Pathology of Corneal Endothelium in Keratoconus

Abstract

Keratoconus is characterized by stromal thinning and conical deformity of the cornea that affects a small but significant portion of the population. Although keratoconus has been well studied, endothehal changes have not been extensively investigated. We studied the endothelium of 14 keratoconus corneal buttons obtained over the past 6 years by penetrating keratoplasty using light microscopy, scanning electron microscopy and transmission electron microscopy. Observations were correlated with patient history. Corneas demonstrated: endothehal cell pleomorphism and polymegathism (6 corneas); endothehal cell degeneration (13), and evidence of anterior chamber inflammation (4). Patterns of endothehal damage were variable ranging from isolated cell membranolysis to denudement of Descemet’s membrane. Less damage was present at the apex of the cones than that observed in a circumferential pattern at the bases. In general the damage observed correlated with the severity and duration of the keratoconus with 9 years being the dividing time between mild and severe endothehal cell damage. These observations support other studies that implicate contact lens wear as a cause of pleomorphism and polymegathism in these patients. Endothehal cell alterations are likely a secondary event occurring due to mechanical stresses.

Corneal Cell Morphology in Keratoconus: A Confocal Microscopic Observation

“…Ucakhan et al and Chi et al observed ploymegathism and pleomorphism in severe keratoconus compared with those in the early stages of keratoconus (4,27). Degenerative and ectatic changes in the later stages of keratoconus can explain the alteration in the usual hexagonal pattern of endothelial cells (27,28). In the present study, the changes observed in endothelial cell density and cell area among the three keratoconus subgroups were not significantly different.…”

Corneal endothelial cell loss after nonmechanical penetrating keratoplasty depends on diagnosis: a regression analysis

“…Wound healing occurs by enlargement, thinning and migration of remaining endothelial cells. The in vivo evaluation of the corneal endothelium normally is performed using contact or noncontact specular microscopy or alternatively confocal microscopy [30,34]. Measurement is impossible if the cornea is no longer clear and the impinging light is scattered in the stroma.…”

The pathogenesis of keratoconus

“…5,7 The minor changes of cellular pleomorphism of the endothelium are most likely secondary to contact lens induced hypoxia or mechanical stress. 8 There is conflicting evidence regarding biochemical abnormalities in KC, with reports of increased, 9 decreased, 10 or normal levels 11 of proteoglycans. Examination of the proteome of KC tissue has confirmed that, compared with normal cornea, there is upregulation of decorin and keratocan.…”