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Thygeson's Superficial Punctate Keratitis
(Thygeson's SPK or TSPK)
First described: Phillips Thygeson. "Superficial Punctate Keratitis".
Journal of the American Medical Association, 1950; 144:1544-1549.
Signs and Symptoms:
Symptoms are minimal, typically these include discomfort such as burning
or irritation, foreign body sensation, mild degrees of tearing, and photophobia
(light sensitivity). There will occasionally be minor decreases in visual
acuity.
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The
typical appearance of the cornea shows numerous superficial lesions
that will stain with fluorescein or rose bengal dye. The epithelium
may be eroded. Lesions may be round, oval or star shaped, they consist
of a conglomerate of tiny grey-white dots that are slightly raised.
Individual lesions are transient and usually are randomly scattered
over the central part of the cornea.
During inactive stages of TSPK, lesions can disappear; can be
flat, grey dots that do not stain; or can appear stellate (star
shaped). The conjunctiva may be mildly red and swollen; tiny hair-like
filaments may be present; and corneal sensation is generally normal
to slightly decreased. (Arffa, p. 323)
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Etiology
The cause of TSPK is unknown but viral or immune mechanisms have been
suggested. "A viral cause has been proposed based on the absence of bacteria
and other infectious agents, the resistance of the disease to antibiotics,
and features that are said to resemble the lesions of measles and adenoviral
infections." (Leibowitz, p.461) However, it should also be noted that
the disease is unresponsive to antiviral agents as well. One author also
notes that the role of the immune mechanism is suggested by the presence
of white blood cells in the conjunctiva and corneal epithelium, "by the
extended course of the disease, by the therapeutic efficacy of topical
corticosteroids," and by the presence in some individuals of an antigen
called HLA-DR3. (Leibowitz, p.461)
Natural History
TSPK tends to have a chronic recurrent course with asymptomatic periods
during which both corneas are clear interrupted by episodes of blurred
vision and minor eye irritation. One remarkable feature is the absence
of any accompanying conjunctivitis. Keratitis is variable with remissions
and exacerbations for several years until it resolves spontaneously, usually
without serious sequellae. (Gock, 1995) "Individual attacks generally
last 1 to 2 months, go into remission for 4 to 6 weeks, and the recur;
the time course is variable. Usually after 2 to 4 years, the disease resolves
without sequelae." (Arffa, p.323) However, rare cases have been reported
to persist for as long as 20 years. It is thought that steroid use is
involved in causing persistence of the disease (see treatment, below).
Treatment
Treatment is only indicated if the patient suffers with significant decreased
vision and/or light sensitivity or pain to be worth the risks of treatment:
development of glaucoma (especially if there is a family history of glaucoma)
or cataract (higher doses of steroids for long periods) or the possibility
of prolonging the TSPK itself..
Lubricant eye drops alone may occasionally relieve symptoms.
The keratitis usually improves with low-dose topical corticosteroids
(0.12% prednisone or equivalent 2 to 3 times per day for a few days
up to 2 weeks as recommended by Arffa, p. 323. Leibowitz et al., recommend
that acute episodes be treated aggressively with topical steroids and
then tapered and discontinued over a 3 to 4 week interval.) It should
be noted that "steroids may prolong the condition and have the risk
of complications in an essentially benign disease." (Gock, p.76). Complications
such as ocular hypertension and cataracts are associated with extended
use of topical corticosteroids. However, the use of steroids may be
warranted in patients who are significantly disabled by the condition
Therapeutic soft contact lenses have been used successfully to treat
the condition but the treatment must be for an extended period of time.
One of the first reports was by Goldberg, et al. who noticed that patients
whose eyes had been bandaged or patched for 24 hours showed considerable
symptomatic relief. This prompted a trial period of therapeutic soft
contact lenses in the patients resulting in "almost complete resolution
of the lesions and dramatic almost immediate relief of discomfort."
(Goldberg, p.23) It has been postulated that soft contact lenses "improve
symptoms by improving the optical quality of the cornea, and cover the
elevated corneal lesions and nerves that are constantly in friction
with the conjunctiva during blinking. The effect would break a vicious
cycle by decreasing lacrimation (tearing) that is associated with hypotonic
(low salt content) tears that may contribute to local epithelial edema
(swelling)." (Tabbara, p. 77) Soft contact lenses may simply protect
the cornea and thus the lesions from exposure and friction.
Outcome/Prognosis
The visual outcome of TSPK is generally good, although some individuals
have experienced slightly reduced visual acuity.
Bibliography
Gock G, Ong K, McClellan K. A classical case of Thygeson's superficial
punctate keratitis. Australian and New Zealand Journal of Ophthalmology.
23(1):76-77, 1995.
Goldberg DB. Schanzlin DJ. Brown SI. Management of Thygeson's superficial
punctate keratitis. American Journal of Ophthalmology. 89(1):22-24,
1980.
Tabbara KF, Ostler HB. Dawson C, Oh J. Thygeson's superficial punctate
keratitis. Ophthalmology. 88(1):75-77, 1981.
Thygeson's Superficial Punctate Keratitis. In Arffa RC. Grayson's Diseases
of the Cornea, 4th ed. Mosby, 1997, pp. 323-329.
Thygeson's Superficial Punctate Keratitis. In Leibowitz HM, Waring
GO. Corneal disorders: clinical diagnosis and management, 2nd ed. Saunders,
1998, pp. 460-461.
Van Bijsterveld OP. Mansour KH. Dubois FJ. Thygeson's superficial punctate
keratitis. Annals of Ophthalmology. 17(2):150-153, 1985.
reviewed
January, 1999, by John E. Sutphin, Jr., MD, Cornea and External Diseases,
Department of Ophthalmology and Visual Science, University of Iowa.
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