MODERN DIAGNOSTIC METHODS AND CLASSIFICATION OF KERATOCONUS (LITERATURE REVIEW)

Abstract

Keratoconus is an ectatic disease of the cornea observed in young individuals of working age, leading to impairment of visual function. In advanced stages of the disease and in cases with a typical progressive clinical course, diagnosis does not present significant difficulty. However, in certain cases, verification of the diagnosis may be accompanied by specific challenges.

This review systematizes contemporary perspectives on the diagnosis of keratoconus and consistently presents current approaches to patient examination and interpretation of the obtained results. In the early stages of keratoconus and in non-progressive forms, the clinical picture (complaints, medical history, visometry, and autorefractokeratometry findings) is identical to that of simple myopia and regular myopic astigmatism. For this reason, it is rather difficult to suspect the presence of the disease. In progressive keratoconus, with the development of keratectasia, the clinical picture acquires characteristics of the disease and essentially reflects the progressive manifestations of irregular corneal myopic astigmatism. The current pathognomonic biomicroscopic signs of keratoconus include the Fleischer pigment ring, Vogt’s stromal striae, and focal corneal thinning around the ectatic apex currently, keratoconus is best diagnosed and screened with computer-based corneal scanners, such as those using a rotating Scheimpflug camera. These devices combine keratoscopy (Placido disc–based imaging) and keratotomography.The proprietary software of keratoanalyzers generates maps of corneal shape irregularity (keratotopography), refractive power maps (keratometry), and thickness maps (keratopachymetry), calculates relevant indices, and evaluates the probability and stage of keratectasia.These diagnostic platforms enable differential diagnosis and verification of keratoconus at the earliest — keratotopographic — stage. However, to date, there is no effective methodology capable of reliably confirming or excluding ultrastructural changes at the pre-keratotopographic stage of keratoconus.