Morphological Changes in Keratoconus: Interpretation of Corneal Confocal Microscopy Findings

The aim of the study was to suggest the interpretation of confocal microscopy findings based on their comparison with a corneal morphological picture, and in accordance with the structural principles of confocal images. Materials and Methods. For 10 year (2005-2015) we monitored and followed up 660 patients with stage I-IV keratoconus (1268 eyes). In addition, 160 patients with subclinical keratoconus (268 eyes) composed a separate group. Corneal discs removed during penetrating keratoplasty were used as the material for paraffin sections to study morphological changes and compare the study results and confocal microscopy findings, confocal microscopy being performed preoperatively. The sections were hematoxylin and eosin stained. To perform corneal confocal microscopy we used a confocal microscope ConfoScan 4 (Nidek Technologies Srl, Japan). Results and Discussion. The most specific signs of subclinical keratoconus were revealed using corneal confocal microscopy. We suggested the concept for interpreting the signs according to the principles of optics and confocal imaging. An optical phenomenon of increased intensity of light reflection by keratocyte nuclei can be due to the light scattering in surrounding tissues. The phenomenon of visible (needle-shaped) deformity of keratocyte nuclei can result from anomaly of spatial orientation of collagen plates. We suggested an interpretation of the light phenomenon of stria formation in corneal stroma in advanced keratoconus and confirmed it with corneal histology. Corneal defects, fibrocellular proliferation and epithelial proliferation were registered in Bowman's membrane, the findings being confirmed by histological analysis of corneal section. Confocal microscopy revealed possible variants of entocornea defect closure. Conclusion. The findings enable to assess the informativity of corneal confocal microscopy, provide an interpretation of the results and confirm it using histological analysis of corneal sections.