KERATOCONUS

Keratoconus is a bilateral noninflammatory corneal ectasia with an inc idence of approximately 1 per 2,000 in the general population. It has well-described clinical signs, but early forms of the disease may go u ndetected unless the anterior corneal topography is studied. Early dis ease is now best detected with videokeratography. Classic histopatholo gic features include stromal thinning, iron deposition in the epitheli al basement membrane, and breaks in Bowman's layer. Keratoconus is mos t commonly an isolated disorder, although several reports describe an association with Down syndrome, Leber's congenital amaurosis, and mitr al valve prolapse. The differential diagnosis of keratoconus includes keratoglobus, pellucid marginal degeneration and Terrien's marginal de generation. Contact lenses are the most common treatment modality. Whe n contact lenses fail, corneal transplant is the best and most success ful surgical option. Despite intensive clinical and laboratory investi gation, the etiology of keratoconus remains unclear. Clinical studies provide strong indications of a major role for genes in its etiology. Videokeratography is playing an increasing role in defining the geneti cs of keratoconus, since early forms of the disease can be more accura tely detected and potentially quantified in a reproducible manner. Lab oratory studies suggest a role for degradative enzymes and proteinase inhibitors and a possible role for the interleukin-1 system in its pat hogenesis, but these roles need to be more clearly defined. Genes sugg ested by these studies, as well as collagen genes and their regulatory products, could potentially be used as candidate genes to study patie nts with familial keratoconus. Such studies may provide the clues need ed to enable us to better understand the underlying mechanisms that ca use the corneal thinning in this disorder. (C) 1998 by Elsevier Scienc e Inc. All rights reserved.).