THICKNESS AND MORPHOLOGICAL CHANGES OF CORNEAL EPITHELIUM IN KERATOCONUS

The primary objective was to evaluate the morphologic and tomographic changes of the corneal epithelium in keratoconus patients according to the stage of keratoconus,the secondary objectives were to examine whether there were any changes on confocal microscopy in forme fruste eyes and to evaluate the subbasal nerve plexus and stroma in addition to the epithelium on confocal microscopy.

Keratoconus group was divided into stage 1,stage 2 and stage 3-4 groups according to Amsler-Krumeich staging.15 patients were included in stage 1 and stage 2 group and 10 patiens were included in stage 3-4 group.In addition,15 patients were included in forme fruste keratoconus group.Participants were evaluated by biomicroscopic examination,anterior segment optical coherence tomography and laser scanner in vivo confocal microscopy.Superficial,intermediate and basal epithelial cells,anterior and posterior stroma keratocyte density,subbasal nerve density and length,dendritic cell density were evaluated.The results were compared between the groups by statistical analysis.

No morphologic difference was observed between the keratoconus group and forme fruste group.The size,circumference and diameter of superficial, intermediate and basal epithelial cells increased in parallel with the stage,while the density and circularity decreased in the keratoconus group compared to the control group.There was a significant decrease in anterior and posterior stroma keratocyte density in the keratoconus group compared to the control group and a significant difference was observed between the stages.Total,main branch and side branch nerve density and total,main branch and side branch nerve length parameters showed a significant decrease in keratoconus stages compared to the control group.There was no significant difference between keratoconus groups and control group in dendritic cell analysis.

In this study,all 3 layers of the epithelium were evaluated in terms of density and cell size between keratoconus stages.It was observed that the basal epithelium was affected early in keratoconus and morphologic changes in the intermediate cell layer and surface cells increased in accordance with the stage.Our findings showing that the basal epithelium is affected at an early stage support previous studies reporting early changes in the basal lamina in keratoconus.Our nerve analysis results are consistent with previous studies reporting a decrease in subbasal nerve density in keratoconus.The fact that no difference was observed in the morphologic evaluation of forme fruste eyes with the control group,which is the secondary objective of our study,indicates that confocal findings in eyes evaluated as normal by OCT-based tomography devices are also normal.