Keratoconus: current diagnostic approach

Keratoconus is an ectatic corneal disease, resulting in loss of visual functions in young population. Diagnosis of the disease at a moderate stage with a typical progressive clinical course is not particularly difficult; however, the diagnosis verification in a few cases is rather troublesome. This literature review systematizes modern conceptions to the keratoconus diagnosis, outlines current approaches to patients examining and diagnostics results assessing. The clinical manifestations (complaints, anamnesis data, visometry and autorefractokeratometry results) at the early stages of keratoconus with its non-progressive course are similar to ordinary myopia and regular myopic astigmatism; as a result, it is quite difficult to suspect the disease in such cases. With progressive keratoconus course, as corneal protrusion develops, the disease acquires features specific for gradual irregular corneal myopic astigmatism growth. Currently valuable pathognomonic slit-lamp signs of keratoconus are Fleischer’s ring, stromal Vogt’s striae and focal thinning of the cornea in the ectasia apex. Nowadays the gold standard of keratoconus diagnosis and screening is comprehensive examination of the cornea by means of modern computer optical scanning (Scheimpflug camera in particular) keratoanalyzers, combining keratoscopy (Placido’s disc) and keratotomography. The keratoanalyzers original software generates maps and calculates irregularity indices of the cornea shape (keratotopography), refractive power (keratometry) and thickness (keratopachimetry), as well as values the probability and stage of corneal protrusion. Such diagnostic platforms provide differential diagnosis and verification of keratoconus at the earliest signs of the topographic stage of the disease; to date, there are no effective methods, that can reliably confirm or exclude ultrastructural changes at the pretopographic stage of keratoconus.