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The paper gives the results of studying the rate of light scattering by different corneal layers in keratoconus from confocal microscopy data. The study was conducted using a Confoscan-4 confocal microscope (Nidek, Japan). The rate of light scattering was estimated from the results of analyzing the densitometric curve, by applying a Z-scanning system. A total of 77 patients (136 eyes) with stages 1-4 keratoconus and 20 healthy individuals at the age of 16 to 20 years were examined. Confocal microscopy revealed corneal changes that were characteristic of different stages of keratoconus and a cause of its optical heterogeneity. As an epithelial lesion progressed, there was an obvious tendency towards increases in the scattering of light waves and in the range between their minimum and maximum values. Examination of corneal stromal layers revealed no statistically significant differences between the minimal level of light scattering in health and that in keratoconus in its different stages. However, there was an increase in the maximum level of light scattering due to the appearance of compact tissue portions with a higher reflectivity. The range between the minimum and maximum values was also increased. Comparison of the levels of light scattering by the posterior corneal epithelium established no statistically significant differences. Overall, increased light scattering by individual corneal microstructures and a distorted ratio between its minimum and maximum levels may be considered as a morphological component of aberrations that reduce the resolution of the eye optical system.

The paper gives the results of a study of ocular optical aberrations in keratoconus. Objective aberrometry was carried out with OPD Scan (Nidek, Japan). An additional computer program (OPD station) was used to evaluate the corneal wavefront. Examinations were made before and after application of a rigid gas-permeable lens (RGPL) to the eye. For the functional evaluation of the effectiveness of contact correction, the investigators used visometry and determined binocular visual functions, contrast sensitivity, and visual productivity. A total of 87 subjects (174 eyes) with keratoconus were examined. Stage 1 disease was found in 48 eyes, Stage 2 in 49 eyes, Stage 3 in 37 eyes, and Stage 4 in 40 eyes. Analyzing the results of the study could evaluation the effectiveness of keratoconus correction with RGPL. The use of the latter presents a possibility of compensating for optical aberrations, achieving their reduction practically to the one level irrespective of the stage of keratoconus with a slight increase in Stage 4 disease. In Stages 1-3, the mean aberration values of each type have very close values (without statistically significant differences between them). In Stage 1 keratoconus, RGPL can completely compensate for high-order corneal aberrations (including coma, trefoil, and spherical aberrations). Normalization of the wavefront promotes the achievement of high functional results of contact correct of refraction disorders in keratoconus, by applying RGPL.