Climatic Keratopathy
Gary N. Foulks
The array of nonhereditary degenerative keratopathy related to geographic or climatic conditions or environmental exposure is vast. Climatic keratopathy is a rubric describing these various entities and presentations. Many of the names encompassed by this term are listed in Table 37-1. The conditions are degenerative corneal changes that share a common pathobiology consisting of elastotic degeneration related to chronic actinic exposure (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28). Yellow, white, or gray lesions typically occur in the interpalpebral area of the superficial cornea, often associated with corresponding changes in the adjacent conjunctiva (21). One classification system divides spheroidal degeneration into three types: type 1 is primary, bilateral, and occurs without other evident ocular pathology; type 2 is secondary and occurs in conjunction with other ocular pathology; type 3 is the conjunctival expression of the disorder and commonly occurs in association with types 1 and 2 (10).
The incidence and severity of climatic keratopathy is geographically dependent, with a higher incidence in areas of high sun exposure. Rural areas usually have higher prevalence and increased severity of disease than metropolitan areas, probably due to differences in occupational sun exposure (17).
CLINICAL DESCRIPTION
Climatic keratopathy is characterized by yellow, oilyappearing subepithelial deposits within the cornea in the interpalpebral area (Fig. 37-1). The changes are usually first visible in the periphery of the horizontal meridian of the cornea. The early appearance is that of minute droplets, appearing like oil, in both nasal and temporal edges of the cornea. Deposits increase in size and number with advancing age and exposure, and may extend across the cornea as a nontransparent band, prompting one description as non-calcific band keratopathy (25,31). Similar deposits in the adjacent conjunctiva are also present but are sometimes less easily recognized (1,4,21). The condition usually occurs in association with pingueculae (1,4,20,21). The deposits initially occur superficially and may replace Bowman’s zone. With advancing severity, the deposits lie deeper in the anterior cornea. Inflammation is usually absent unless secondary erosion or superinfection occur.
Symptoms are usually mild, particularly if only the periphery is involved with the deposits, but when the deposits occur centrally vision can be reduced (Fig. 37-2). Elevations of the deposits can result in desiccation of the corneal surface due to disturbance of the tear film, resulting in symptoms of foreign-body sensation and irritation. If aggravating local factors are present, the cornea may break down and ulceration can occur. Secondary infection also is a potential complication, and corneal perforation has been reported (32).
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