Summer 2000 IJO vol3, #1.qxd

...........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1 ... page 1

Indiana University School of
Optometry Administration:

Gerald E. Lowther, O.D., Ph.D.,

Dean

Clifford W. Brooks, O.D., Director,

Optician/Technician Program

Daniel R. Gerstman, O.D., M.S.,

Executive Associate Dean for

Budgetary Planning and

Administration

Steven A. Hitzeman, O.D., Director

of Clinics

Edwin C. Marshall, O.D., M.S.,

M.P.H., Associate Dean for

Academic Affairs

Jacqueline S. Olson, B.A., M.A.,

Director of Student Affairs

Sandra L. Pickel, B.G.S., A.S.,

Opt.T.R., Associate Director,

Optician/Technician Program

P. Sarita Soni, O.D., M.S.,

Associate Dean for Research

and Graduate Program

Graeme Wilson, O.D., Ph.D.,

Associate Dean for Graduate

Programs

Indiana Journal of Optometry

Editor:

David A. Goss, O.D., Ph.D.

Editorial Board:

Arthur Bradley, Ph.D.

Clifford W. Brooks, O.D.

Daniel R. Gerstman, O.D., M.S.

Victor E. Malinovsky, O.D.

Neil A. Pence, O.D.

News Item Editor:

Andrya H. Lowther, M.A.

Production Manager:

J. Craig Combs, M.H.A.

Statement of Purpose: The

Indiana Journal of Optometry is

published by the Indiana

University School of Optometry

to provide members of the

Indiana Optometric Association,

Alumni of the Indiana University

School of Optometry, and other

interested persons with

information on the research,

clinical expertise, and activities

at the Indiana University School

of Optometry, and on new

developments in

optometry/vision care.

The Indiana Journal of

Optometry and Indiana

University are not responsible

for the opinions and statements

of the contributors to this

journal. The authors and

Indiana University have taken

care that the information and

recommendations contained

herein are accurate and

compatible with the standards

generally accepted at the time

of publication. Nevertheless, it

is impossible to ensure that all

the information given is entirely

applicable for all

circumstances. Indiana

University disclaims any

liability, loss, or damage

incurred as a consequence,

directly or indirectly, of the use

and application of any of the

contents of this journal.

A TRIBUTE to Jack W.

Bennett ................................. 2

FACULTY PROFILE: Arthur

Bradley, Ph.D........................ 4

FEATURED REVIEW: The

Changing Face of Refractive

Surgery, by Arthur Bradley.... 5

EYE OPENER: The Optical

Science Underlying the

Quantification of Corneal

Contour: A Short History of

Keratoscopy and Indiana

University Contributions, by

David A. Goss and Daniel R.

Gerstman............................ 13

REVIEW OF ARTICLE OF

INTEREST: Review by David

A. Goss: Progressive Addition

Lenses for Myopia

Control................................. 17

NEWS ITEMS: News from the

IU School of Optometry, by

Andrya H. Lowther............... 19

Please contact us with your comments or suggestions by

calling 812-855-4440 or emailing us at
IndJOpt@indiana.edu.

Summer 2000

Volume 3, Number 1

Table of Contents

Cover Photo: Photokeratogram

taken with the

Keracorneascope, a

photokeratoscope which was

marketed with an optical device

called a comparator for analysis

of the pictures; a short history

of keratoscopy starts on page

13.

Page 2 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ..........................................................

arlier this year Optometry mourned the loss of one of its most ardent advocates, Jack W.

Bennett. Anyone who met him would readily note his friendly and jovial Hoosier manner. But

beneath the folksy humor of his Granddaddy Barndollar stories and self-deprecating remarks,

there was an man of insight and of commitment to family and profession.

Jack W. Bennett was born on October 23, 1932 in Bloomington, Indiana. He graduated in 1950

from Bloomington High School.  Bennett attended Indiana University from 1950 to 1952.  In 1952, he
married Alice Bauer of Bloomington.  Alice became an active helpmate to Jack in optometric
activities.  For example, she became the president of two state optometric auxiliaries and national
president of the American Foundation for Vision Awareness.

Bennett served as an optical technician in the United States Army for three years during the

Korean War. He returned to Indiana University in 1955, and completed his Bachelor of Science
degree in 1958 and his Master of Optometry degree in 1959.

Bennett practiced optometry in Bloomington from 1959 to 1970. During this period of time he

was also a part-time Clinical Associate in the IU Division of Optometry and was very active in the
Indiana Optometric Association, serving as its president in 1968-1970. In 1970, he left private
practice to become Associate Professor of Optometry at Indiana University, a position he held until
1975. Bennett was Director of Patient Care for the IU Optometry Clinics from 1970 to 1972. While

serving on the IU faculty, Bennett received the
Distinguished Service to Optometry Award from the
Indiana Optometric Association (1974) and Indiana
Optometrist of the Year award (1975).

In 1975 Bennett left Indiana to serve as the Dean for

the new College of Optometry at Ferris State University in
Big Rapids, Michigan.  Despite the challenges of a state
economy tied to the auto industry, the school survived and
prospered under Bennett’s leadership.  He served Ferris
State in various administrative capacities in addition to
being Dean of the College of Optometry, including
Executive Assistant to the President in 1986-87 and Vice
President for Administrative Affairs in 1987-88.  He was
president of the Michigan Association of the Professions in
1986-87 and president of the Association of the Schools
and Colleges of Optometry in 1987-89.  While working in
Michigan, Bennett received the Professional Man of the
Year Award from the Michigan Association of the
Professions (1983) and the Keyman Award from the
Michigan Optometric Association (1984).

In August of 1988, Bennett returned to Indiana

University to serve as Dean of the School of Optometry.

This provided opportunities to return to his roots and to
again attend IU basketball and football games regularly,
as well as to make new contributions to optometry. In the

first issue of the Indiana Journal of Optometry, Bennett looked back on the developments in the IU
School of Optometry during his years as Dean.1 He noted changes such as restructuring of the
faculty as a unit rather in a departmental structure, the recognition of the need for clinical rank
faculty, the encouragement of practicing optometrists to mentor bright men and women of their
communities concerning optometry as a profession, revision and expansion of the curriculum,
increases in clinical experience opportunities for students, facility upgrades, increased electronic
technology, investments in research, improved relations with alumni, increased activity of faculty in

Jack Winn Bennett, 1932-2000

A Tribute

Jack W. Bennett

...........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1 ... page 3

optometric organizations, and equipment improvements.

During his years as Dean at IU, Bennett continued teaching in the classroom, lecturing on such

topics as optometric ethics, practice management, and optometric history. These years saw him
receive Meritorious Service and Lifetime Achievement Awards from the Indiana Optometric
Association, and he was named a Sagamore of the Wabash by Indiana Governor Frank O’Bannon.
In 1998, Bennett reached the mandatory retirement age for administrators at Indiana University.

When Bennett stepped down as Dean at IU, he was planning to serve on the IU optometry faculty

for some time and then retire.  These plans were put on hold when the University of Missouri - St.
Louis convinced him to serve as the Dean of their School of Optometry.  He was Dean there from
January of 1999 to April of 2000, when he became ill.  His condition rapidly worsened, and he died at
his home in Bloomington on April 28, 2000.  A memorial service, held May 20, 2000 at the First
United Methodist Church in Bloomington, was reflective of things that mattered to Jack Bennett: one
of his nine grandchildren offering a musical prelude, former optometric colleagues giving words of
eulogy, and two of his four children making touching and humorous tributes.  Memorial contributions
can be made to the Jack W. Bennett Endowed Scholarship Fund at Indiana University, the Jack W.
Bennett Memorial Fund at Ferris State University, the Jack W. Bennett Scholarship Fund at
University of Missouri - St. Louis, or the Creutzfeldt-Jakob’s Disease Foundation.

The Editor

Reference
1. Bennett JW. Reflections. Indiana J Optom 1998; 1: 2-5.

Dr. Gordon Heath, Dr, Jack Bennett, and Dr.
Henry Hofstetter, the first three Deans of the
IU School of Optometry.

Dr. Bennett holding the Sagamore of
the Wabash awarded to him at his
retirement May, 1998

Page 4 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana University Journal of Optometry ........................................

fter what he describes as the longest hitch-
hiking trip of his life, Dr. Bradley arrived in
Berkeley, California to join the Ph.D.
program in Physiological Optics at the

School of Optometry in 1976. Up to that point in
time he had never met or spoken with an
optometrist, but as an undergraduate at the
University of Reading, in England he had
developed a deep interest in the human visual
system which spurred him to pursue a research
degree.

He arrived in Berkeley confident in his own

"perfect vision", only to lose a bet with another
recently arrived Ph.D. student, Raymond
Applegate, an IU School of Optometry graduate
who correctly identified Dr. Bradley as a latent
hyperope. Dr. Bradley now describes his
refraction as the "jock" prescription typical of one
who spent most of his youth chasing soccer, rugby
or cricket balls when he should have been hitting
the books.

At Berkeley, Dr. Bradley studied under

numerous IU alumni (Drs. Tony Adams, Ian Bailey,
Richard VanSluyters, and Russ and Karen
DeValois). He pursued his Ph.D. thesis on human
amblyopia with Ralph Freeman in whose lab he
also studied the neurophysiology of primary visual
cortex and vision in amblyopia.

Dr. Bradley financed most of is graduate

career by teaching virtually every physiological
optics lab in the curriculum, and lecturing at U.C.
Berkeley and U.C. Santa Cruz on visual optics and
visual perception. After graduating with a Ph.D.,
he worked with the DeValois group on color vision,
after which he joined the faculty of Indiana
University. His decision to come to IU was greatly
influenced by his contact with many IU alumni in
Berkeley.

Since arriving at IU in 1985, Dr. Bradley has

developed a world-renown research laboratory
studying visual perception and visual optics. He
has specialized in applying the basic science of
optics and vision to interesting clinical problems. It
was this expertise that led to his "Glenn A Fry"
award from the American Optometric Foundation,
and his recruitment onto the Federal Drug
Administration (FDA) advisory panel on
Ophthalmic Devices.

In addition to a research career with over 100

publications, Dr. Bradley has continued his long-
standing interest in and commitment to teaching.
He teaches the monocular and binocular visual
function courses within the O.D. curriculum, and

contributes to other courses in visual optics,
contact lenses, and environmental optics. He also
teaches a wide variety of courses within the Visual
Sciences program. His commitment and expertise
have been recognized by the students with a
"Professor of the Year" award, and by the
University with two "Teaching Excellence
Recognition Awards".

He was part of a special team put together to

advise the Department of Defense on the suitability
of PRK for service personnel, and within the FDA,
he has advised on numerous refractive devices
and procedures. It is primarily his experience
within this environment that prompted him to write
the article on refractive surgery in the current issue
of the Indiana Journal.

Arthur Bradley, Ph.D.

Profile:

Arthur Bradley, Ph.D.

........................................Indiana University Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1 ... page 5

he recent diversification and availability of

refractive surgery has initiated the most

significant change in refractive technology

since the popularization of the contact lens

during the 1960s. Just as the contact lens freed the

myope from the spectacle, refractive surgery may

free the myope from spectacles and contact lenses.

In spite of its coverage in the popular press (e.g.,

articles in Time magazine and Consumer Reports), it

is not easy to keep abreast of the data on and

changes in refractive surgery. Optometrists are often

provided with pseudo-scholarly publications that are

actually promotional literature1 published by those

marketing refractive surgery. It is this environment of

biased and difficult to access information, that

motivated Dr. Bradley, who is a member of the FDA

Ophthalmic Devices panel and Professor of

Optometry and Vision Science at Indiana University

to write a short summary of the recent history and

new developments in this field.

Some prominent ophthalmologists such as

George Waring III are concerned about the mismatch

between the reality of refractive surgery and the

promotional marketing literature2: "the patient must

have realistic expectations of the procedure based on

honest communication from the surgeon and

professional staff, regardless of portrayal of the

procedure in advertising and the popular media".

There are lingering doubts about the reliability,

safety and stability of refractive surgery. For

example, Professor of Ophthalmology, Leo Maguire,

has referred to patients who have undergone

refractive surgery as the "refractive underclass"3.

Also, there are sufficient numbers of patients

dissatisfied in their refractive surgery results that they

have their own web page. This web page

(http://www.surgicaleyes.org) is full of testimonials

and even some computer simulations of post-

refractive surgery vision which are worth seeing.

In spite of the lingering concerns about refractive

surgery it continues to be promoted and has become

a real option for many patients, some of who will seek

advice from their Optometrist prior to deciding on

surgery. This article is designed as an up-to-date

short review of this field to help our readers

understand the benefits, shortcomings, and possible

future of this approach to correcting ametropia.

The optometrists role in laser vision correction: TLC,

Laser Eye Centers, 1999.

Waring G III, Future developments in LASIK. In:

Pallikaris I, Siganos D, eds. LASIK, Thororofare, NJ: Slack ,

1998: 367-370.

Maguire L, Quoted in Consumer Reports article on

LASIK titled "Zap your myopic eyes", June, 1999.

Introduction:

Although most spherical refractive errors are

caused by anomalous axial length (too long in

myopes and too short in hyperopes), there is a long

history of correcting for this anatomical defect by

introducing optical changes at the anterior eye. For

centuries, spectacle lenses were the only option

available to make this change, but during the last half

of the 20th century, contact lenses became a

convenient alternative and are currently worn by over

20 million Americans. These lenses work by

changing the curvature at the air-eye interface, where

the refractive index difference is large and most of the

eye’s optical power exists. A similar and more

permanent strategy is to change the curvature of the

anterior corneal surface directly.

Although refractive surgery (Keratotomy) was

pioneered during the nineteenth century, it was not

widely available until the last quarter of the 20th

century. Several methods for implementing corneal

curvature changes were developed during the last

quarter of the 20th century and continue to be

developed today. Early methods, e.g., radial

keratotomy (RK) in the 1970’s and 80’s and

photorefractive keratectomy (PRK) in the 1990’s, had

serious shortcomings and they are now being

replaced.

For example, RK, in addition to poor

predictability, produced eyes with unstable refractive

errors that varied diurnally and with altitude and on

average shifted towards hyperopia after surgery (e.g.,

almost 50% shifted by 1 diopter). This article will

describe some of the more recent surgical

approaches and in particular will examine the

refractive success and the safety issues associated

with each.

Refractive surgeries designed to reshape the

cornea can be grouped by either the site of surgical

intervention or the surgical method. For example, in

treating myopia, RK and PRK differ in both the site of

intervention and the surgical method. RK makes

incisions deep into the peripheral cornea, while PRK

The Changing Face of Refractive

Surgery

by Arthur Bradley, Ph.D.

removes tissue from the anterior central cornea using

a high-energy ultraviolet laser.

Photoablative Refractive Surgery

Most photoablative corneal reshaping techniques

employ UVB lasers, e.g., an argon fluoride excimer

laser (

λ=

193 nm), to produce high-energy radiation

which is highly absorbed by the corneal stroma. This

energy is sufficient to break the chemical bonds that

form the collagen fibers and effectively remove this

tissue from the cornea.

Initial attempts to use UV lasers were based upon

the RK radial incision technique. However, the UV

laser failed as a "knife" because it created wider

incisions than the scalpel and produced more

significant scars. More recently, the UV excimer laser

has been modified to ablate stromal tissue within the

optical zone and thus reshape the optical surface

directly. Two manifestations of this approach have

been developed, Photorefractive Keratectomy (PRK)

and laser in situ keratomileusis (LASIK), and both

share a common goal, to reshape the anterior corneal

surface by ablating stromal tissue. However, the

methods for achieving this goal are quite different.

In PRK, anterior stromal tissue is ablated after

the corneal epithelium has been scraped away

(although in rare cases transepithelial PRK was

performed). Of course, this method also ablates the

basement membrane (Bowman’s Layer) upon which

the epithelium grows, and thus has a number of

undesirable complications associated with loss of

epithelial function including susceptibility to infection,

post-surgical pain, abnormal epithelial growth, and

reduced optical transparency. These problems are

most pronounced in the period after surgery, and thus

patients did not generally have bilateral PRK, but had

to maintain one untreated eye during the epithelial

recovery period. In spite of this protracted recovery

period, PRK surgery has been performed on both

eyes simultaneously.

The problems associated with destruction of the

epithelium in PRK have been largely eliminated by

implementing a different pre-ablation surgical

procedure. Instead of scraping off the epithelium, a

deep cut into the stromal lamellae is made

approximately parallel to the corneal surface using a

micro-keratome (LASIK). The cut begins temporally

or inferiorly and cuts across the central cornea but

leaves the nasal or superior edge uncut (the flap).

This method produces an anterior corneal flap (70-

160 microns thick), which can be folded back to

expose the corneal stroma. At this point a

photoablative method, the same in principle to that

used in PRK, is employed to remove stromal tissue

and thus reshape the corneal stroma without

destruction or removal of the epithelium. Once the

ablation is complete, the flap can be repositioned

over the remaining stroma resulting in a cornea with a

mostly functioning epithelium (some sensory nerve

damage and associated corneal insensitivity occurs,

which remediates after about two weeks). The flap is

a non-rigid structure and when repositioned its shape

is affected by the underlying stromal re-shaping which

is transferred to the anterior corneal surface thus

changing the optical power of the cornea.

LASIK is currently the most widely used surgical

method for correcting refractive errors and several

commercial lasers have received FDA approval.

LASIK Efficacy

If refractive surgery is effective, the post-surgical

refractive errors should be the same as the targeted

or intended refractive error. The reason to use

targeted or intended instead of emmetropia is that

sometimes emmetropia is not the target. For

example, a patient may elect to have a small amount

of myopia to aid in reading.

Many studies report and plot the average post-

surgical refractive error, and in general with more

recent technology this approaches the target

indicating an almost perfect outcome. However,

individual eyes do not achieve the mean post-op Rx,

and therefore, in order to assess efficacy, the post-

surgical refractive errors of individual eyes must be

considered.

In order for the FDA to approve a photoablative

laser for LASIK, it must be able to demonstrate

efficacy by having a high percentage of the post-

surgical refractions within some range of the intended

or target refraction (e.g., 75% must be within 1 diopter

of intended and 50% within 0.50 diopters). Most

current systems achieve this goal, with about 60-70%

of the eyes ending up within 0.50 D of the target and

sometimes more than 90% within 1 diopter.

However, some studies still report less than 75%

within 1 diopter of target.

In general, the anticipated residual refractive

errors increase with the magnitude of the pre-surgical

refractive error. However, although approximate

emmetropia may not be achieved in some highly

myopic eyes, it can be argued that converting a -10

diopter myope into a -2 D myope is an effective

procedure since their level of visual disability while

uncorrected will be greatly reduced.

It is important, therefore, that patients be fully

aware of the likely refractive outcome prior to opting

for surgery. Realizing that a patient will typically

expect to leave their eye-care practitioner’s office

seeing "perfectly", clinicians counseling patients

about refractive surgery should emphasize that this

will probably not happen. Typical results in recent

studies indicate about 80% to 90% of patients end up

Page 6 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana University Journal of Optometry ........................................

with uncorrected VA (UCVA) of 20/40 or better, and

between 40 and 70% with 20/20 or better UCVAs.

The FDA requires a new laser system to demonstrate

20/40 UCVA in at least 85% of treated eyes to qualify

as effective. That is, perhaps 50% of LASIK patients

will have to tolerate uncorrected VAs poorer than

20/20 or wear a spectacle or contact lens to achieve

their pre-surgical VA. As many patients with low

levels of refractive error now do, these post LASIK

patients with small residual refractive errors generally

choose to leave them uncorrected making the clear

choice of convenience over vision quality.

There is one significant complication associated

with efficacy. Since photoablation removes tissue,

there will always be some wound healing process,

and this can and does lead to post-surgical refractive

instability. Since PRK removed the entire epithelium

and Bowman’s layer, the healing process was very

active, and this was the likely cause of much of the

post surgical instability. The reduced wound healing

response experienced with LASIK results in less post-

surgical instability in Rx, most eyes (e.g. 95%)

experiencing less than 1 diopter change during the

year post surgery. Recent protocols have reduced

the population mean change in Rx to almost zero.

However, some individual eyes do experience

changes during the 6 months post-surgery.

Although LASIK does not require complete re-

growth of the corneal epithelium and the wound

healing is reduced, recent studies have observed

increased epithelial thickness anterior to the ablation

indicating some epithelial response to the surgery or

the ablation.

Of course, efficacy will be compromised by any

change in corneal structure following keratomileusis

or photoablation, and the significant reduction in the

thickness of the remaining structurally intact cornea

does seem to have an effect. For example, bowing of

the posterior corneal surface has been reported and

this may reflect structural changes caused by the

removal of more than 100 microns with the keratome

and up to 200 microns with photoablation, reducing

the 500 micron thick cornea to approximately only

200 mechanically integrated microns. A significant

correlation between bowing and residual stromal

thickness has been observed when the thickness is

less than 290 microns. The same study concluded

that inaccuracies in the refractive outcome stem

primarily from a combination of secondary bowing

and epithelial thickness changes that develop post-

surgically. Leaving less than 250 microns intact is

generally felt to be unsafe.

The primary determinant of efficacy is the amount

and spatial distribution of tissue ablated. This often

depends upon proprietary algorithms, which can be

updated to improve efficacy if a procedure has been

shown to either under or over correct. Very simply, if

the pre-ablation anterior corneal curvature is known,

the desired change in refraction determines the

required new curvature and the amount of tissue to

be removed. Studies have shown how much tissue

will be ablated by a given amount of laser energy

(e.g. 0.1 microns can be removed by a 50 mJ/cm2

excimer laser pulse), but these values vary slightly

from eye to eye depending upon such things as

stromal hydration. An additional source of variability

is eye position and eye movements during surgery.

In response to this concern, some laser systems (e.g.

Autonomous flying spot laser) include an eye position

tracking system to effectively stabilize the eye with

respect to the laser. This system corrects for any eye

movements during the procedure, which can last from

few seconds to 60 seconds depending on the amount

of tissue to be ablated.

One major advantage of PRK over RK is that,

unlike RK, it did not suffer from significant diurnal

fluctuations or the significant hyperopic shifts

associated with high altitudes that plagued RK.

Recent studies by the US military at 14,000 ft. have

confirmed that LASIK eyes do not suffer from the 1.5

diopter hyperopic shifts seen in RK eyes, but if an eye

has had LASIK recently, a hyperopic shift of about 0.5

diopters was observed. However, after six months,

no such shift was observed.

Since the mean post-LASIK Rx has approached

zero, it appears that the tissue ablation algorithms

have been optimized. The fact that the majority of

eyes do not end up emmetropic results from the eye-

to-eye variability in such factors as epithelial growth,

corneal bowing and reaction to the laser. Therefore,

in order to improve the efficacy still further, a two step

surgery may have to be implemented. The second

ablation will fine tune the small errors left after the

first LASIK. However, the second procedure is nearly

as costly as the first and reduces profit margins.

Such an approach is already used to correct "poor

outcomes" after the initial LASIK procedure.

LASIK Safety

Evaluation of safety is more complicated than

assessing efficacy of refractive surgery. We can

consider any change to the eye which compromises

vision as a safety problem. There are five general

categories of such problems following LASIK: (1)

infections and pathology in response to the surgical

or/and ablative procedures, (2) undesirable wound

healing responses, (3) photoablative changes that

cannot be corrected with standard spectacle or

contact lenses, (4) effects of the high energy laser on

other ocular tissues, and (5) optical problems

.........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1 ... page 7

associated with the pre-ablation surgery (e.g. flap

irregularities). Due to the invasive nature of this

surgery, it is not surprising to find that problems

associated with the flap surgery are the most

significant.

Post-surgical pathology:

The incidence of infections caused by LASIK is

very low, and includes bacterial keratitis due to poor

ocular hygiene combined with imperfect epithelial

coverage along the flap incision. Vitreous

hemorrhage and retinal detachments following

corneoscleral perforations resulting from the surgical

microkeratome have also been reported, but again,

the incidence is very low (e.g., 2 eyes out of 29,916).

Other vitreoretinal pathologies in the post-surgical

LASIK patients were also very rare and may reflect

typical levels experienced by highly myopic eyes.

This emphasizes that, although LASIK may correct

the myopic refractive error, it does not treat or prevent

the other problems associated with and caused by

increased axial length in myopic eyes. Dry eye is a

very common complaint following LASIK, possibly

due to cutting the corneal nerves and decreasing the

primary signal that produces normal tear levels. Dry

eye complaints persist for a long time and individuals

with dry eye prior to surgery should be counseled that

LASIK may exacerbate their existing problem. Those

without dry eye should be counseled that dry eye

complaints are relatively common and can last for

several months to a year following surgery.

Wound healing response:

Diffuse interface keratitis, with an accumulation of

inflammatory cells at the flap interface has been

observed presumably due to a wound healing

response. Also, unusual epithelial growth has been

observed when trauma dislodges the flap. Recent

evidence from animal studies indicates that the

healing process at the flap interface continues for

about 9 months after LASIK. The consequences of

this prolonged wound healing are unclear.

Optical changes uncorrectable with standard

ophthalmic lenses:

There is a genuine concern that photoablative

procedures will result in reduced optical quality of the

cornea due to either a loss of transparency and

optical scatter or irregular changes in the shape of the

optical surface. Both of these optical changes are

uncorrectable with standard spectacle lenses.

Aberrations exist in an optical system when, even

with an optimum sphero-cylindrical correction, the

rays forming a point image will not focus to a single

point. Increased optical aberrations reported in post-

PRK and post-LASIK eyes4 may reflect the

algorithms used to create the ablations, but other

factors must also be involved. For example, myopic

"islands" are often reported after PRK or LASIK and

for some reason these local under-corrected areas

seem to disappear over time. The cause of these

myopic islands and the mechanisms behind their

remediation are not well understood.

As a check for such detrimental changes in the

cornea, the FDA requires that post LASIK VAs be

determined with the optimum spectacle correction in

place (Best Spectacle Corrected Visual Acuity:

BSCVA). If an eye can no longer be corrected to its

pre-surgery levels of VA, it is likely that one or both of

the above optical changes have occurred. The FDA

requires that less than 5% of eyes lose more than 2

lines of BSCVA, and less than 1% end up with

BSCVA of worse than 20/40. One might argue that

any loss of BSCVA is unacceptable since it is

essentially an untreatable vision loss. It is, however,

disappointing that after centuries of striving to

improve retinal image quality, we are now willing to

accept reduced retinal image quality and significant

loss of vision all in the name of convenience.

Although current standards tolerate reduced

retinal image quality and the current LASIK protocols

increase the eye’s aberrations, the potential is there

to reduce aberrations and actually improve retinal

image quality. In principle, photoablative techniques

can be used to correct not only the eye’s spherical

and cylindrical refractive errors but also higher order

aberrations such as spherical aberration and coma,

which limit retinal image quality in pre-surgical eyes.

Autonomous Technologies is pioneering this concept,

which requires measurement of the eye’s aberrations

in addition to the refractive error typically measured.

We expect to see this approach, referred to as

"custom cornea" to develop rapidly in the next few

years. Of course, in order to correct for the

aberrations, they must first be measured. New

technology borrowed from astronomy has been

successfully employed to measure ocular

aberrations5 and these can be used to guide

photoablative surgeries. The term "wave-guided

corneal surgery" was recently coined to describe this

procedure.

We shall soon see if wave-guided corneal

surgery can succeed. McDonald presented some of

the first data earlier this year and showed that the

increase in aberrations and thus reduction in retinal

image quality associated with the standard LASIK

procedure may not occur following a "custom cornea"

approach. Currently, it is not clear how successful

this approach will be. It may be a way to maintain

optical quality at pre-surgical levels, but the potential

is there for actual improvement.

Although the ablation algorithms may be perfect

and corneal transparency maintained, there is

Page 8 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ........................................................

another factor that will lead to significant loss of

retinal image quality in LASIK or PRK. In order to

maintain a monofocal optical system, the reshaped

cornea must be larger than the eye’s entrance pupil.

However, there are limits to the maximum size of the

ablation zone because increased ablation zone size

requires deeper ablations. For example, by

increasing the ablation zone from 4 mm to 7 mm

approximately doubles the necessary ablation depth

in the central cornea when correcting myopia. Thus,

correction of large refractive errors requires more

tissue ablation and larger ablation zones also require

deeper ablations. For example, Sher calculated that

300 microns of tissue would have to be removed to

correct a -12 diopter myopia over a 7 mm diameter

area. Approximate corneal thinning caused by

photoablation for myopia is 12, 18 and 25 microns

per diopter with 5, 6, and 7 mm ablation zones,

respectively.

The problems associated with leaving too little

attached stroma after ablation are exaggerated with

LASIK since up to 150 microns of the anterior cornea

has been removed already in the flap. Ablating

significant amounts of the remaining stromal tissue

may compromise the structural abilities of the

remaining stroma and result in the observed "bowing"

of the posterior corneal surface after surgery.

Since there are limits to how much corneal tissue

can be safely removed, ablation zone size has

typically been smaller than necessary to cover the

entire dilated pupil present at night. Current

standards try to maintain at least 250 microns of

intact stroma after photoablation. Given this type of

constraint, the photoablation zone size is limited.

Early PRK photoablations were performed with 4 mm

and 5 mm zones, but the standard now is about 6 mm

with perhaps a 1-2 mm "transition" zone. Because

the pupil of many young eyes will be larger than 6

mm under low light conditions, the effective optical

system creating the retinal image will be bifocal. The

central zone will be near to emmetropic and the

marginal zone near to the pre-ablation refractive

error. Although this has obvious parallels to

simultaneous bifocal contact lenses or IOLs, it is not

an effective bifocal correction since the additional add

power in the peripheral optics will vary from eye to

eye and will be too peripheral to be effectiveat high

light levels. This bifocal problem cannot be corrected

with a spectacle lens or easily corrected with a

contact lens and bifocal optics are known to produce

significantly reduced image quality, halos and glare.

Data over the last few years indicate that the

flattening of the central cornea by LASIK actually

leads to steepening of the peripheral cornea

potentially exaggerating the simultaneous bifocal

effect for larger pupils. Also, by adding transition

zones into the surgical procedure, a dilated pupil

produces multifocal optics.

The impact of post-surgical simultaneous bifocal

or multifocal optics would only be manifest at low light

levels, and studies from Europe seem to indicate that

night vision can be significantly compromised by PRK

and LASIK. Visible halos and glare at night are often

reported, and they increase in frequency with

increased myopic correction, and cases have been

reported in which post LASIK and post PRK night

vision is so poor that night driving has to be

eliminated. It would be wise therefore, as Applegate6

has been emphasizing for many years now, to

discourage individuals with large night-time pupils

from undergoing this procedure. Simulations of these

night vision problems can be visualized on the web at

http://www.surgicaleyes.org.

UV damage to other ocular tissue:

The introduction of a high intensity UV radiation

source into the eye produces obvious concerns for

other ocular tissue since UV is known to cause

cataractogenesis and may be a significant factor in

age related maculopathy. However, 193 nm UV

radiation does not penetrate more that a few microns.

This is why it is so effective at stromal ablation.

Problems with the flap.

The major concern with LASIK stems from the

radical surgery preceding the photoablation. The

entire anterior cornea (epithelium and part of the

stroma) is removed across the central cornea

exposing the central stroma. Problems develop due

to poor quality of the keratome blade, poor control of

the cutting speed, failure to complete the cut, leaving

tiny metal fragments from the blade on the flap,

deposition of other material (e.g., surgical glove

powder) within the wound, and movement of the

tissue during the cut. Expert use and maintenance of

the micro-keratome is essential to reduce the

incidence of these vision-compromising

complications.

It is important to realize that cutting corneal tissue

requires much greater precision and better quality cut

surfaces than cutting tissue in other parts of the body.

Errors, such as the micro-chatter marks seen post

LASIK, on the scale of the wavelength of light, can

become significant. Also, since the stroma is

avascular, there is little opportunity for debris to be

removed by phagocytic inflammatory cells. Reports

of tiny metal fragments from the micro-keratome

blade, powder from the surgical gloves, small pieces

of sponge as well as corneal tissue remnants have

been seen under the flap post surgically. All of these

reduce transparency, and can require a second

procedure in which the flap is opened up and the

.........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1 ... page 9

tissue cleaned.

LASIK has a unique safety issue not present with

other refractive surgical procedures, which stems

from the structural weakness of the corneal flap and

its poor adhesion to the underlying corneal stroma. In

some ways it is remarkable that the flap can

"reattach" so easily without sutures. Initial

reattachment results from hydrostatic pressure due to

the hydrophilic nature of the inner cornea. Primary

"reattachment" forces may result from capillary

surface tension. It is therefore quite easy to remove

the flap for additional photoablation, if the initial

surgery was not as effective as desired. However,

the flap can also become dislodged accidentally.

Remarkably, this is very rare, but it can and does

happen, usually following some ocular trauma. A

notable concern exists for patients with dry eye who

may experience adhesion forces between the anterior

corneal surface and the lid. This has led to a patient

waking to find the flap stuck to the lid. Also, because

of the reduced sensitivity following surgery (sensory

nerves have been cut) the normal feed-back that

controls corneal insult has been seriously

compromised which must increase the chances of

elevated mechanical forces on the cornea due to

trauma or lid friction.

In addition to flap displacement, the structural

weakness of the flap and its attachment can lead to

structural changes within the flap. Small scale

"ripples" or "wrinkles" in the flap have been reported,

as have larger folds. Flaps are sometimes detached

and reattached to try and remedy flap irregularities.

There is also the problem of accurately realigning the

flap and replacing it in the correct location. Flap

decentration has been reported. As with flap

wrinkling, it will lead to reduced optical quality.

The final complication associated with the flap

surgery stems from the pre-incision protocol. In order

for the keratome to make a precise cut, the corneal

tissue must be held firmly by a vacuum ring. During

this procedure, the intraocular pressure spikes to

above 60 mm of Hg. There is some concern that this

IOP spike, particularly if it is maintained for more than

a few seconds, can lead to retinal damage. Suction

duration depends upon the speed of the procedure

and can vary significantly (e.g., from 6 to 80

seconds). Changes in retinal blood flow and visual

function following this transient elevated IOP have

been reported. In addition to the IOP spike, there is

some globe deformation associated with the vacuum

ring.

In the March 2000 issue of Biophotonics

International, a new technology for producing the flap

without a micro-keratome was described. A group at

the University of Michigan are developing an infra-red

laser to make the flap. This device uses a highly

convergent laser beam with very high energy per

square cm at its focal plane with sufficient energy to

break the collagen fibers. By placing the focal plane

within the stroma and scanning across the eye, the

anterior cornea can be detached from the remaining

posterior stroma and a flap produced. The

advantages are that it requires no mechanical shear

forces, which tend to move and distort the cornea and

lead to variable flap thickness with micro-keratomes.

Also, by optically adjusting the laser focal plane, the

flap depth can be varied across the cornea and flaps

with beveled edges can be produced. The

technology is undergoing trials in Europe and may be

introduced late in 2000 in the US. Interestingly for

optometry, this device removes the necessity for

cutting tissue with a blade, or traditional surgery, and

may, in the classical sense, make LASIK a non-

surgical procedure.

LASIK Summary

The overall picture emerging from the LASIK

literature indicates that it is a largely safe and

effective treatment for myopia, hyperopia and

astigmatism. However, LASIK is not risk free, and

with current technology final vision quality will

probably be slightly inferior to pre-surgical vision.

Night vision may be significantly impaired. There are

many stories of post-PRK and post-LASIK patients

having to modify their night driving behavior because

of seriously reduced vision at night. For the patient,

the very small risk of serious complications and the

likely small reduction in vision and night driving

problems must be balanced against the obvious

convenience of never having to worry about contact

lenses or spectacles. Perhaps more significantly,

highly myopic patients will never have to suffer the

serious handicap that exists when their high myopia

is uncorrected. For many patients, particularly those

who are seriously handicapped by their myopia, and

those for whom highest quality vision is not required,

this may be the surgical treatment of choice at this

time. However, it is imperative that all patients are

made aware of the risks, particularly the commonly

occurring reduced quality of vision and night driving

problems.

Thermokeratoplasty

In addition to the photoablative use of short

wavelength UV lasers, corneal irradiation using long

wavelength (1.5 - 2.0 micron) lasers has been

developed to create thermally induced changes in the

corneal stroma. This method, Laser

Thermokeratoplasty (LTK), has some obvious

parallels to radial keratotomy, and it is sometimes

referred to as radial thermokeratoplasty. Unlike RK,

which treated myopia by introducing deep incisions to

Page 10 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ........................................................

allow the peripheral cornea to stretch and thus reduce

central corneal curvature, LTK causes peripheral

corneal shrinkage due to thermally induced shrinkage

of individual collagen fibers. Thus, LTK has the

opposite effect on the peripheral cornea, and therefore

induces myopic shifts in the central cornea. It has

been suggested and actually tested as a treatment for

hyperopia (either naturally occurring or secondary to

over-correction by PRK or LASIK), but it is still in the

investigational stage and has not received FDA

approval. There are major concerns about its ability to

produce a stable refractive change since large

regressions occur. Also, unlike photoablative

techniques which calculate the desired tissue to be

removed, LTK must rely on empirically determined

nomograms. Predictability with this approach has not

been established and dosimetry studies continue to

examine the impact of wavelength, temperature,

penetration of the radiation, beam profile, and spatial

pattern and duration of radiation. There is also

concern that the thermal effects cannot be confined to

the stroma, and damage to the epithelium and

endothelium may occur.

Surgical Implants

In addition to the methods just described in which

the cornea is reshaped by removing tissue or

reshaping the cornea, two new surgical approaches

are being developed that insert foreign bodies into the

eye. The first inserts a ring deep into the peripheral

corneal stroma and the second involves implanting an

intraocular lens (IOL) into a phakic ametropic eye.

Intrastromal Corneal Rings

Just as RK and LTK change the curvature of the

central cornea by changing the structure of the

peripheral cornea, intrastromal corneal rings (ICR) or

intrastromal corneal ring segments (ICRS) are inserted

into the peripheral cornea to treat myopia. The ring or

ring segments are inserted through a small incision

and threaded circumferentially into the deep stromal

lamellae. The structural changes that are produced

translate into curvature changes in the central cornea.

Inserting PMMA annular rings into the deep stromal

lamellae of the corneal periphery changes the already

prolate elliptical cornea into an even more prolate

cornea, reducing the overall corneal curvature and

thus producing a hyperopic shift. Studies indicate that

myopia of up 3 or 4 diopters can be treated with this

method. The biggest advantage of this approach is

that, unlike PRK, RK or LASIK, it is largely reversible

by simply removing the ring (segments). Thicker rings

(0.45 mm diameter) introduce large changes and thus

can correct for more myopia while thinner rings (0.25

mm) are used to correct lower levels of myopia.

BSCVAs seem to remain high and thus the method

must not introduce large amounts of aberrations or

turbidity in the central cornea. There is some concern

that significant refractive instability exists with this

method including diurnal variations. Peripheral

corneal haze, small lamellae deposits adjacent to the

ring, deep stromal neovascularization, and pannus are

also associated with the ring insertions. Currently the

FDA has approved one ICR (Keravision’s Intacs).

Phakic Intraocular Lenses

Unlike the previous methods, which all required

the development of new technology, IOL implantation

has a long and successful history as a treatment for

cataract. The major difference with phakic IOL

implantation is that the natural lens is left in place.

The general principle of using an IOL to correct for

ametropia has of course been part of the typical

cataract lens replacement regime for many years. By

manipulating the curvature, refractive index and

thickness of an IOL, significant refractive errors can be

corrected by the cataract surgery.

A phakic IOL (PIOL) is placed in either the anterior

or the posterior chamber and anchored in a similar

way to that of traditional IOLs. PIOLs are made of

flexible materials such a silicone and hydrogel-

collagen, and can be anchored with nylon haptics or

other mechanical anchors. The anterior chamber

PIOLs typically anchor in the angle between the

cornea and iris while posterior chamber PIOLs anchor

around the zonules. One beneficial effect of

transferring the myopic correction from the spectacle

to the iris plane is that there will be significant image

magnification which is responsible for the observed

improvements in VA after this procedure.

The primary concerns with phakic IOLs stem from

the intrusive nature of the surgery in an eye that does

not need to be opened and the introduction of a

foreign body into the eye. For example, the

acceptably low levels of complications associated with

cataract surgery may be unacceptably high for phakic

IOL refractive surgeries. Also, recurring problems with

lenticular and corneal physiology, the development of

cataracts, and reduced endothelial cell counts cast

doubt on the acceptability of this approach for routine

refractive surgery.

The efficacy of this approach hinges on the

application of thick lens optics and accurate biometric

data on the eye. There is still some uncertainty in

calculating the required PIOL power and therefore the

post surgical refractions are not very accurate with

residual errors of up to 6 diopters. These inaccuracies

are, of course, affected by the precise position of the

lens in the eye, and this can vary significantly from eye

to eye.

There are two primary safety issues that continue

to compromise this approach. First, posterior chamber

..........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1... page 11

Page 12 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ........................................................

PIOLs that are typically in contact with both the lens

and the iris, routinely lead to cataract development.

Incidence rates of up to 80% have been reported, but

other studies report zero incidence of cataract.

Anterior chamber PIOLs seem to lead to reduced

endothelial cell counts and thus compromise the

physiology of the cornea, and in some cases (20% of

eyes in one study) have lead to the surgical removal

of the PIOL. Also, the posterior chamber PIOLs push

the iris forward and thus lead to reduced anterior

chamber depth (and volume) and narrower angles

with the associated elevated chance of angle closure

glaucoma. Also, oval pupils and glare problems have

been reported following insertion of anterior chamber

PIOLs.

The major advantage of this approach over the

corneal reshaping techniques described previously is

that it can correct for very large refractive errors, and

has been used to correct eyes with up to -30 D of

myopia and +10 of hyperopia. One interesting

combination therapy for the very high myopes has

been to implant a PIOL to correct most of the myopia

and then use the more predictable LASIK to further

reduce the myopia towards emmetropia.

One solution to the cataract development

complication associated with posterior chamber

PIOLs is to remove the natural lens and replace it

with one that will correct the refractive error.

PIOLs have not received FDA approval although

several are in the last phases of FDA approved

clinical trials.

Summary:

Refractive surgery has been widely available for

about three decades now, and it has undergone many

transformations. Overall, the newer techniques have

improved accuracy, stability and reliability, but

continue to be plagued by biological variability leading

to small errors in correction. Although serious

problems rarely occur with PRK or LASIK, minor

problems associated with reduced optical quality are

routinely produced. Eye care practitioners should

advise patients of the small risks of serious

complications and the high risk of slight daytime

vision problems and possible serious night driving

problems. These risks must be balanced with the

tremendous increase in convenience of reducing or

eliminating dependence on spectacle or contact

lenses.

The costs associated with excimer lasers and the

imperfect results observed with PRK and LASIK are

the primary driving forces behind the continued

development of novel refractive surgical techniques

and products, and we can expect to see more

developed in the future.

Post-script

Most of the information reported in this review

article comes directly from the primary literature.

Refractive surgery has proliferated a large number of

publications. For example, 330 articles were

published on LASIK during the last five years. I used

over 50 such articles identified by searching through

the National Library of Medicine’s MEDLINE system

to write this article. I have not included all of these

citations, but a comprehensive bibliography on these

topics can be located at

http://www.ncbi.nlm.nih.gov/PubMed/ simply by

searching for PRK, LASIK, PIOLs, etc. Also, the year

2000 abstract listings from the annual meeting of the

Association for Research in Vision and

Ophthalmology (ARVO) proved to be a valuable

resource (http://www.arvo.org).

Acknowledgements:

Earlier drafts were improved with help from Raymond Applegate,

O.D., Ph.D. (Indiana Alumnus), Professor of Ophthalmology,

University of Texas, San Antonio; Michael Grimmett, M.D. Assistant

Professor of Ophthalmology, University of Miami; and by Carolyn

Begley, O.D., M.S., and David Goss, O.D., Ph.D. from the Indiana

University Optometry faculty.

Three important papers published by IU faculty

and alumni on refractive surgery:

4. Oshika T, Klyce SD, Applegate RA, Howland HC, El Danasoury

MA, Comparison of corneal wavefront aberrations after

photorefractive keratectomy and laser in situ keratomileusis.

Am J

Ophthalmol, 1999; 127:1-7.

5. Thibos LN and Hong X Clinical applications of the Shack-

Hartmann aberrometer. Optom Vision Sci 1999; 76: 817-825.

6. Applegate RA and Gansel KA The importance of pupil size in

optical quality measurements following radial keratotomy. Corneal

Refract Surg 1990; 6:47-54.

he Indiana University School of
Optometry has been active for a number
of years in the optical science underlying
the quantification of corneal contour.
The first IU graduate student to earn a

Ph.D. degree in physiological optics, Robert B.
Mandell, did his dissertation research on
instrumentation and measurement of corneal
topography. In 1962, Mandell completed his
Ph.D. thesis, "Morphometry of the
Human Cornea." Mandell has gone
on to publish material on corneal
topography in books and journals.1-
3 In 1961 at IU, John R. Levene
completed an M.S. thesis entitled
"An Evaluation of the Hand
Keratoscope as a Diagnostic
Instrument for Corneal Astigmatism."
In 1965, Levene published the
definitive work on the history of the
invention of keratoscopy.4

Studies

on corneal contour by IU optometry
faculty include a subjective
evaluation of keratoscopy images.5

The Indiana University School of

Optometry got involved early in
videokeratoscopy when it obtained a
Corneal Modeling System in the late
1980s. Purchase of this
videokeratoscopic system was made
possible by a grant of $89,900 to
Drs. Dan Gerstman, Gordon Heath,
Doug Horner, and Sarita Soni from
the Indiana Lions Eye Bank, Inc.6
The Corneal Modeling System
captures light information reflected
from the cornea in the form of
concentric rings, and digitizes this
information to produce a color map of corneal
dioptric power, thus providing a local radius of
curvature.

Indiana University faculty members have

published on reliability, validity, and
mathematical analysis in keratoscopy,7-9 as
well as on applications of videokeratoscopy in

patient care and clinical research.10-14 IU
faculty have also written book chapters on
keratoscopy procedures and corneal topography
analysis.15,16 Tom Salmon, a 1999 IU Ph.D.
graduate, used videokeratoscopy and other
instrumentation to analyze the contributions of
the cornea to the aberrations of the eye,
culminating in his Ph.D. dissertation entitled
"Corneal Contribution to the Wavefront

Aberration of the Eye". Recent
instrumentation obtained by IU
includes the Orbtek, Inc., Orbscan,
which yields anterior corneal surface
contour measures, corneal thickness
maps, and back surface curvature
estimates.

A variety of factors influenced the

significant gain in popularity of
photokeratoscopy and
videokeratoscopy in the 1980s and
1990s. Computers have made the
analysis of keratoscopy images quick

and simple, thus allowing the use of

corneal topography measurements
for monitoring keratoconus and
various other corneal conditions in a
timely fashion. Corneal topography
has also been used extensively to
study the effects of orthokeratology
and keratorefractive surgery. While it
may seem that photokeratoscopy is a
recent development, the Swedish
ophthalmologist, Allvar Gullstrand
(1862-1930) worked out the optical
concepts of photokeratoscopy over a
hundred years ago.

Keratoscopy has its roots in the

development of keratometry.

Keratometry is based on the principle that the
radius of curvature of a convex surface is
proportional to the size of an image reflected
from that surface. It appears that this principle
was first applied in 1619 when Christoph
Scheiner measured the radius of curvature of

The Optical Science Underlying the
Quantification of Corneal Contour: A
Short History of Keratoscopy and Indiana
University Contributions

David Goss, O.D., Ph.D. and Daniel Gerstman, O.D., M.S.

Daniel R. Gerstman

David A. Goss

..........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1... page 13

the anterior corneal surface by comparing the
sizes of images reflected from the cornea to
images reflected from glass balls of known
radius.17,18 The first keratometer was
constructed by Jesse Ramsden, an instrument
maker, in 1769.19 Subsequently, in the mid 19th
century, Hermann von Helmholtz improved on
Ramsden’s design and made a keratometer (or
ophthalmometer as it was called then) that was
similar to the manual keratometers of today.
Whereas the optically centered keratometer
predicts the radius of curvature across a span of
about 3 mm relying on just four localized points
(two per meridian), the centered keratoscope
provides an assessment of almost the entire
corneal surface, utilizing thousands of localized
points reflected from the cornea and analyzed for
most all meridians.

Levene4 identified English physician Henry

Goode as the
first to make a
keratoscope.
Goode reflected
a square object
from the
patient’s cornea
and viewed the
reflection from
the side of the
keratoscope
target. Goode
was influenced
by George
Biddell Airy’s
description of
astigmatism,
and in 1847
Goode reported
on his
observations of
some eyes with
astigmatism
using his
keratoscope.

By studying

publications
and letters to
the editor in 19th century journals, Levene4
concluded that the Portuguese oculist Antonio
PlÆcido independently reinvented a hand
keratoscope in 1880, and also invented the
photokeratoscope in 1880. PlÆcido’s
keratoscope had black and white concentric
circles and a viewing tube in the center of the
keratoscope used for alignment. His pattern of
alternating black and white rings is used in

modern corneal topographers with the target
often referred to as a PlÆcido’s disc.  French
ophthalmologist Emile Javal was the first to
suggest using auxiliary lenses to magnify the
keratoscope image.  Javal talked about attaching
a paper disc with concentric circles either to an
ophthalmoscope along with a plus lens, or to the
Javal-Schiotz ophthalmometer (keratometer), or
to a photographic system.  Javal was the first to
use a keratoscope to evaluate a corneal disease,
when he examined an eye with keratoconus.

Gullstrand’s contribution came in 1896 in

being the first to describe the mathematical
analysis of photokeratoscopy.20 Ludlam and
Wittenberg,20 in their 1966 translation and notes
on Gullstrand’s photo-keratoscopy system,
observed some faults in Gullstrand’s work, but
stated that Gullstrand’s "...work still stands as the
best in photo--keratoscopy. Little has been done

since then
which
approaches
the insights
offered by
Gullstrand..."
Today
computerized
photo-
keratoscopy
and video-
keratoscopy
units have
programs to
calculate
various
parameters of
corneal
topography.
Gullstrand had
already
worked out a
system for
these
calculations in
1896. But
without rapid
calculation

capability as is made possible today with
computers, Gullstrand recognized that the
necessary calculations would be too tedious for
the typical ophthalmic practice. In talking about
measurements of the cornea in his appendices
to Helmholtz’s Treatise on Physiological Optics
published in 1909, Gullstrand stated: " The only
way to do this, when the problem consists in
ascertaining the radii at different points in one

Gullstrand s photokeratoscopy apparatus, Today s videokeratoscopes

look a little different! (Used by permission from: Gullstrand A.

Photographic-ophthalmometric and clinical investigations of corneal

refraction, translated by Ludlam WM,, with appendix notes by

Wittenberg S. American Journal of Optometry and Archives of the

American Academy of Optometry, 43(3): 143-214.

The American

Academy of Optometry, 1966.

Page 14 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ........................................................

and the same principal section, is by
photographing the reflex image in the cornea.
Such measurements, it must be admitted, take
much time and require special apparatus made
for the purpose. Consequently, they are not
suitable for the general run of practice, but on
the other hand they give a resultant accuracy
that previously could not be obtained in any
other way."21

Gullstrand’s photokeratoscope target was a

series of paired concentric circles.  Each circle
had another paired circle very close to it with a
thin dark line between them.  To measure radii
of curvature in the horizontal and vertical
meridians, Gullstrand moved a microscope over
the photographic plates by means of a screw
mechanism.  A "dividing engine"22 was used to
determine the amount of movement of the
microscope after it had been moved to align a
cross hair in the ocular with the dark line
between the paired white circles.  These
measurements were converted into radii of
curvature and then into dioptric powers.  In his
1896 paper, Gullstrand gives an example of a
photograph taken and analyzed in 1893.  He
presented an x,y coordinate plot of dioptric
power as a function of degrees of eccentricity.
This kind of plot had been produced previously
with peripheral ophthalmometry (keratometry),
but Gullstrand appears to have made the first
such plot using keratoscopy.  Although today’s
keratoscopy is often thought of as a recent
development, Gullstrand had worked out many
of the necessary details over a hundred years
ago.

Perhaps because of the lack of rapid

calculation methodology for the extensive
computations and/or Gullstrand’s statement that
photokeratoscopy measurements "..are not
suitable for the general run of practice...," little
work seems to have been done in this area in
the first couple decades of the twentieth century.
It appears that the first commercial device for
photokeratoscopy was manufactured by Zeiss in
the 1930s.23,24 The Zeiss instrument had a flat
target so curvature of field would have affected
peripheral measurements. Zeiss did not resume
manufacture of the instrument after World War
I

The next commercially available device for

photokeratoscopy was the Wesley-Jessen
Photo-Electronic Keratoscope or PEK.25,26 I

was developed in the 1950s, and was
manufactured for about 20 years. Because the
target rings were on an elliptical bowl, there
were less curvature of field defects than with the

Zeiss instrument.  Wesley-Jessen marketed the
PEK as an aid to contact lens fitting.  The
practitioner took the keratoscope picture and
mailed it to Wesley-Jessen.  Wesley-Jessen
sent back an analysis of the corneal topography
and suggested the appropriate contact lens
parameters.  Although possibly more accurate
than the Zeiss instrument, the PEK did not
achieve wide acceptance.

Following the PEK, various photo-

keratoscopes were available, including the
Corneascope and the Nidek Photo-

keratoscope.15,27 The Corneascope was
marketed initially by International Diagnostics
Instruments and later by Kera Corporation. The
practitioner could analyze photokeratograms
taken in the office with a device called a
Comparator.28,29 The Comparator is an optical
magnifier with variable magnification. The
Comparator projects the Corneascope
keratogram onto a screen and allows the
practitioner to compare the photokeratogram
rings to a calibrated set of concentric rings.
Radii of curvature at various points on the
photograph can be determined by varying the
magnification to match the photograph ring size
to the ring size on the comparison pattern.

..........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1... page 15

Allvar Gullstrand (1862-1930) was winner of

the Nobel Prize in physiology or medicine in

1911. He made many contributions to the

knowledge of optics of the eye and lenses

and to instrumentation for ophthalmic

clinical practice. This medal, from the

collection of Jay M. Galst, was struck by Erik

Lindberg in 1935 for the Royal Swedish

Academy of Science. (photo courtesy of Jay

M. Galst)

The next developments focused on replacing

photographs with computer scanning devices
coupled with video technology.  It appears that
the first computerized videokeratoscope was the
Corneal Modeling System by Computed
Anatomy.16,30 It was this instrument that was
obtained by Indiana University School of
Optometry in the late 1980s.  IU now has the
newer generations of this and other
videokeratoscopic instruments.  There are a
number of videokeratoscopes now on the
market.  Most use the Placido pattern for the
object and an image analysis system similar to
that of Gullstrand’s.  Even though computer
technology has allowed keratoscopy to become
more widely accepted and more clinically
friendly, the basic principles underlying the new
technology are the same as those articulated by
Gullstrand.  Gullstrand’s approach developed
over a hundred years ago is finally being
incorporated into "the general run of practice."

References

1. Mandell RB. Corneal topography. In: Mandell RB,

ed. Contact Lens Practice, 4th ed. Springfield, IL:

Charles C. Thomas, 1988: 107-135.

2. Mandell RB. The enigma of the corneal contour.

Contact Lens Assoc Ophthalmol J 1992; 18: 267-273.

3. Mandell RB, Horner D. Alignment of

videokeratoscopes. In: Sanders DR, Koch DD, eds.

An Atlas of Corneal Topography. Thorofare, NJ:

Slack, 1993: 197-204.

4. Levene JR. The true inventors of the keratoscope

and photo-keratoscope. Brit J Hist Sci 1965; 2: 324-

342.

5. Hofstetter HW. A keratoscopic survey of 13,395

eyes. Am J Optom Arch Am Acad Optom 1959; 36: 3-

11.

6. Anonymous. School acquires Corneal Modeling

System. Optometry Alumni Focus 1989; 13(2): 1.

7. Heath GG, Gerstman DR, Wheeler WH, Soni PS,

Horner DG. Reliability and validity of

vidoekeratoscopic measurements. Optom Vis Sci

1991; 68: 946-949.

8. Salmon TO, Horner DG. Comparison of elevation,

curvature, and power descriptors for corneal

topographic mapping. Optom Vis Sci 1995; 72: 800-

808.

9. Horner DG, Salmon TO. Accuracy of the EyeSys

2000 in measuring surface elevation of calibrated

aspheres. Internat Contact Lens Clin 1998; 25: 171-

177.

10. Horner DG, Soni PS, Heath GG, Gerstman DR.

Management of scarred cornea with RGP contact

lens. Internat Contact Lens Clin 1991; 18: 9-12.

11. Soni PS, Gerstman DR, Horner DG, Heath GG.

The management of keratoconus using the corneal

modeling system and a piggyback system of contact

lenses. J Am Optom Assoc 1991; 62: 593-597.

12. Horner DG, Heck D, Pence NA, Gilmore DM.

Terrien’s marginal degeneration: A case report with

corneal modeling evaluation. Clin Eye Vision Care

1992; 4:64-69.

13. Horner DG, Bryant MK. Take another look at

today’s ortho-k. Rev Optom 1994; 131(6): 43-46.

14. Horner DG, Soni PS, Vyas N, Himebaugh NL.

Longitudinal changes in corneal asphericity in myopia.

Optom Vis Sci 2000; 77: 198-203.

15. Goss DA. Keratoscopy. In: Eskridge JB, Amos JF,

Bartlett JD, eds. Clinical Procedures in Optometry.

Philadelphia: Lippincott, 1991: 379-385.

16. Horner DG, Salmon TO, Soni PS. Corneal

topography. In: Benjamin WJ, ed. Borish’s Clinical

Refraction. Philadelphia: Saunders, 1998: 524-558.

17. Ronchi L, Stefnacci S. An annotated bibliography

on corneal contour. Firenze: Baccini & Chiappi, 1975.

18. Daxecker F. Christoph Scheiner’s eye studies.

Doc Ophthalmol 1992; 81: 27-35.

19. Mandell RB. Jesse Ramsden: inventor of the

ophthalmometer. Am J Optom Arch Am Acad Optom

1960; 37: 633-638.

20. Gullstrand A. Photographic-ophthalmometric and

clinical investigations of corneal refraction.

(Translated by Ludlam WM, with appendix notes by

Wittenberg S) Am J Optom Arch Am Acad Optom

1966; 43: 143-214.

21. Gullstrand A. Procedure of rays in the eye. In:

Southall JPC, ed. Helmholtz’s Treatise on

Physiological Optics, translated from the third German

edition (1909). New York: Dover, 1962; 1: 309.

22. Daumas M. Scientific Instruments of the

Seventeenth and Eighteenth Centuries and their

Makers (Translated and edited by Holbrook M).

London: Portman Books, 1989: 194-204.

23. Emsley HH. Optics of Vision, Volume 1 of Visual

Optics, 5th ed. London: Butterworths, 1953: 330-331.

24. Knoll HA. Photokeratoscopy and corneal contours.

In: Haynes PR, ed. Encyclopedia of Contact Lens

Practice. South Bend, IN: International Optics, 1961; 2

(9th supplement): 6-11.

25. Reynolds AE, Kratt HJ. The photo-electronic

keratoscope. Contacto 1959; 3: 53-59.

26. Henson DB. Optometric Instrumentation, 2nd ed.

Oxford: Butterworth-Heinemann, 1996: 132.

27. Rowsey JJ, Reynolds AE, Brown R. Corneal

topography - Corneascope. Arch Ophthalmol 1981;

99: 1093-1100.

28. Reynolds AE. Introduction: History of corneal

measurement. In: Schanzlin DJ, Robin JB. Corneal

Topography: Measuring and Modifying the Cornea.

New York: Springer-Verlag, 1992: vii-x.

29. Lundergan MK. The Corneascope-Comparator

method of hard contact lens fitting. In: Schanzlin DJ,

Robin JB. Corneal Topography: Measuring and

Modifying the Cornea. New York: Springer-Verlag,

1992: 117-128.

30. Gormley DJ, Gersten M, Koplin RS, Lubkin V.

Corneal modeling. Cornea 1988; 7: 30-35.

Page 16 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ........................................................

ecades of research on childhood myopia
progression still haven’t yielded any
definitive answers on how progression rates
can consistently be controlled. However, it

is widely accepted that nearwork plays a role in
myopia development, as evidenced by the
recent publication of two books on the
relationship of myopia and nearwork.1,2
Laboratory studies with animals have shown
that myopia can be induced by the defocus of
retinal imagery.3-6 The physiological correlate
in humans to these animal models of defocus-
induced myopia may be large lag of
accommodation during nearwork. Myopic
children and young adults tend to have lower
accommodative response levels than
emmetropes and hyperopes.1,2,7,8 If defocus
associated with high accommodative lag plays a
role in the etiology of human myopia, then the
prescription of added plus for near becomes a
logical approach to myopia control.

A recent paper by Leung and Brown9 reports

progressive addition lenses to have a significant
effect in reducing childhood myopia progression
rates.  The study was conducted at The Hong
Kong Polytechnic University Optometry Clinic
where potential subjects were selected by
review of the clinic records.  Subject inclusion
criteria were: nine to twelve years of age, one to
five diopters of myopia, astigmatism less than or
equal to 1.50 D, anisometropia less than or
equal to 1.25 D, intraocular pressure less than
20 mm Hg, monocular visual acuities better than
6/9, stereoacuity better than 100 seconds of arc,
and myopia progression greater than -0.4
diopters per year.  None of the subjects had
strabismus or had a correction for large phorias.
All subjects wore spectacles prior to the study.
Seventy-nine subjects started the study, and 68
completed the full two years of the study.
Subjects were examined at six month intervals
during the investigation.

The control group wore single vision spectacle

lenses. There were two progressive addition
lens treatment groups: one with +1.50 D reading
additions and one with +2.00 D reading
additions. Subjects were advised to wear their

glasses full-time. When subjects had a change
in spherical equivalent refraction of 0.37 D or
greater, they received new lenses with the new
prescription. The examiner was not masked to
the treatment group or to the previous
prescription.

Study Findings

Refractive error measurements were made by

manifest subjective refraction, and the right eye
spherical equivalent was used for analysis.  The
mean increase in myopia in two years for the
single vision lens wearing control group was -
1.23 D (n=32; SD=0.51).  The subjects who
wore +1.50 D adds had a mean change in
refractive error of -0.76 D (n=22; SD=0.43).
This was significantly different from the mean
change for the control group (p=0.0007).  The
subjects with the +2.00 D add treatment had a
mean two year progression of myopia equal to -
0.66 D (n=14; SD=0.44).  This was also
significantly different from the mean for the
control group (p=0.0007).  The means for the
+1.50 D and +2.00 D add groups were not
significantly different (p=0.505).

The depth of the vitreous chamber was

measured by ultrasonography. The
enlargement of eyes of control group subjects
was greater than that for subjects who wore
progressive addition lenses. The mean
increases in vitreous chamber depth were 0.63
mm (SD=0.40) in the single vision lens group,
0.46 mm (SD=0.34) for the +1.50 D add group,
and 0.41 mm (SD=0.41) in the group wearing
+2.00 D adds.

Comments

This appears to be the first published paper

on the use of progressive addition lenses for
slowing childhood myopia progression. In the
extensive literature on bifocals for myopia
control, study outcomes have been variable.
One consistent result in four studies is that
mean progression rates were about 0.2 diopters
per year less with bifocals than with single vision
lenses in children with esophoria at near on the
von Graefe test.10,11 Phorias were not

reported

Article of Interest: Progressive Addition
Lenses for Myopia Control

Review by David A. Goss, O.D., Ph.D.

Leung JTM, Brown B. Progression of myopia in Hong Kong Chinese schoolchildren is slowed by wearing

progressive lenses. Optom Vis Sci 1999; 76(6): 346-354.

..........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1... page 17

Page 18 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ........................................................

in this paper.

The examiner was not masked to subject

treatment group in this study, so it could be
argued that inadvertent examiner bias could
have affected the refractive error results.
However, the vitreous depth increases show the
same trend of less change in the progressive
addition lens groups than in the single vision
lens group.

The amount of reduction in myopia

progression rates with progressives in this study
(about a quarter diopter per year) is greater than
that found in most of the bifocal studies without
division by phoria status.10,11 It is unknown
whether this was due to the population studied
or unrecognized variables or whether
progressives may be more effective in myopia
control than bifocals. One possible advantage
of progressive addition lenses in this regard is
that parents may more readily accept
progressives than bifocals. Most children adapt
successfully to progressive addition lenses.

Nearpoint plus can be beneficial in non-

presbyopes with conditions such as
convergence excess and accommodative
insufficiency. This study suggests that
nearpoint plus in the form of progressive
addition lenses can also be useful in myopia
control.

References
1. Ong E, Ciuffreda KJ. Accommodation,
Nearwork and Myopia. Santa Ana, CA:
Optometric Extension Program, 1997.
2. Rosenfield M, Gilmartin B, eds. Myopia and
Nearwork. Oxford: Butterworth-Heinemann,
1998.
3. Wallman J. Retinal factors in myopia and
emmetropization: clues from research on chicks.
In: Grosvenor T, Flom MC, eds. Refractive
Anomalies: Research and Clinical Applications.
Boston: Butterworth-Heinemann, 1991: 268-
286.
4. Goss DA, Wickham MG. Retinal-image
mediated ocular growth as a mechanism for
juvenile onset myopia and emmetropization.
Doc Ophthalmol 1995; 90: 341-375.
5. Wildsoet CF. Active emmetropization -
evidence for its existence and ramifications for
clinical practice. Ophthal Physiol Opt 1997; 17:
279-290.
6. Smith EL III. Environmentally induced
refractive errors in animals. In: Rosenfield M,
Gilmartin B, eds. Myopia and Nearwork. Oxford:
Butterworth-Heinemann, 1998: 57-90.

7. Goss DA, Zhai H. Clinical and laboratory
investigations of the relationship of
accommodation and convergence function with
refractive error - a literature review. Doc
Ophthalmol 1994; 86: 349-380.
8. Gwiazda J, Bauer J, Thorn F, Held R. A
dynamic relationship between myopia and blur-
driven accommodation in school-age children.
Vis Res 1995; 35: 1299-1304.
9. Leung JTM, Brown B. Progression of myopia
in Hong Kong Chinese schoolchildren is slowed
by wearing progressive lenses. Optom Vis Sci
1999; 76: 346-354.
10. Goss DA. Effect of spectacle correction on
the progression of myopia in children - a
literature review. J Am Optom Assoc 1994; 65:
117-128.
11. Grosvenor T, Goss DA. Clinical
Management of Myopia. Boston: Butterworth-
Heinemann, 1999: 113-125.

..........................................................Indiana Journal of Optometry ... Summer 2000 ... Vol. 3, No. 1... page 19

Dr. Victor Malinovsky recently received

the Indiana University’s President’s Award for
Excellence in Teaching during the Founder’s Day
ceremony.  He was the only recipient from the
Bloomington campus.  This is a very competitive
University system award and the first time that
an Optometry School faculty member has
received it.  The award is a tribute to Dr.
Malinovsky’s many years of hard work in the
classroom, his development of the ocular
disease clinic, and his national reputation in
professional continuing education.

Dr. Ed Marshall was recently chosen by the

U.S. Public Health Service to receive the
prestigious 2000 Primary Care Policy Fellow.  He
is one of 32 individuals from around the country
and world chosen for this fellowship.  This is a
very competitive process and Dr. Marshall is the
second optometrist to ever be chosen for this
program.  This is a great honor for him, the
School of Optometry, and the optometry
profession.  The program brings together a multi-
disciplinary group of primary health care leaders
to work with top government, congressional, and
private sector health care officials in Washington,
D.C.  Dr. Marshall will be making a number of
additional visits to Washington in conjunction
with this program.

Dr. Sarita Soni was recently appointed to

the National Advisory Eye Council. This group
advises the Secretary of Health and Human
Services; the Director, NIH; and the Director,
NEI, on all policies and activities relating to the
conduct and support of vision research, research

training, facilities development, and other
programs of the Institute.

Thomas Stickel, a fourth year optometry

student, was
recently named
a recipient of the
Indiana
University John
H. Edwards
Fellowship.
There were only
five recipients
from the entire
Indiana
University. The
amount of the
fellowship was
approximately
$14,000. Tom

also was recently

named the Chancellor’s Scholar from the School
of Optometry.

Dr. Ed Marshall recently received a

$99,000 grant from the Indiana State Department
of Health under the Preventive Health and Health
Services Block Grant program. The application
is to equip an examination room in the Family
Health Center of Clark County, the Patoka
Family Healthcare Center in Crawford County,
and the Martin County Health Clinic in Shoals.
These facilities target the under-served, low-
income residents.

News from the IU

School of Optometry

U.S. Surgeon General David Satcher, Dr.Norma
Bowyer, HHS Secretary Donna Shalala, and Dr. Ed
Marshall.

Tom Stickel

The Family Health Center of Clark County, IN, site

of the optometry exam room funded by Dr.

Marshall s grant.

Page 20 ... Vol. 3, No. 1 ... Summer 2000 ... Indiana Journal of Optometry ........................................................

Dr. Doug Horner was an invited lecturer at

the B.P Koviala Lions Centre for Opthalmic
Studies’ optometry program in Kathmandu,
Nepal recently. Since the library at the Centre
had very few optometric publications, the faculty
of IU School of Optometry, under Dr. Horner’s
guidance, is now contributing publications to the
Centre in Nepal.

An official ribbon cutting ceremony was

held on March 8 at the opening of the new
Indiana University optometry clinic at the
Hospital General in Guanajuato, Mexico. The
event was presided over by Mrs. Maria Esther
Montes de Martin, President of the Department
of Infants and Family (DIF); Professor Martha
Aguilar Gomez, Director General of DIF; and Dr.
Carlos Tena Tamayo, Secretary of Health.

Representing the IU School of Optometry at the
ceremony were Dr. Cyndee Foster who is the
faculty member in charge of the clinic, and Dr.
Doug Horner, who has been instrumental in
establishing the clinic. This clinic will be a
rotation site for fourth year interns from Indiana
University as well as for interns from The Ohio
State University.

Drs. Joe Bonanno, Susana Chung, and

Larry Thibos were recipients of sizeable grants
from National Institute of Health (NIH) recently.

Drs. Jerry Lowther and Sarita Soni

lectured at the American Academy of Optometry
International meeting in Madrid, Spain in April.

Dr. Sarita Soni will present at the Essilor

200 Presbyopia Conference in Portugal n June
and also at the International Society of Contact
Lens Specialists meeting in Switzerland in
September.

Approximately 30 of our faculty and

students presented papers, posters, and
continuing education at the American Academy
of Optometry in Seattle this past December. In
addition, Dr. Sarita Soni and Dr. Jerry
Lowther served on the Executive Council, Dr.
Vic Malinovsky was the chairperson of the
Ellerbrock Continuing Education program, and
Dr. Larry Thibos was in charge of the AAO web
site. Indiana University was, indeed, well
represented at the AAO.

Approximately 20 of our faculty and

students will present papers and posters at the
Association for Research in Vision and
Ophthalmology (ARVO) annual meeting in Fort
Lauderdale the end of April.

Mrs. Maria Esther Montes de Martin, President of

DIF and Dr. Carlos Tena Tamayo, Guanajuato s

Secretary of Health and Medical Director of DIF

cut the ribbon to the new Eye Care Center in

Guanajuato.

Hospital General, Guanajuato, Mexico where our Eye clinic is located.