keratocyte density in keratoconus and post-lasik corneas with and without keratectasia; a confocal scan study

purpose: to compare keratocyte density in stromal layers of the cornea in keratoconus, post-lasik keratectasia, lasik without keratectasia, and normal corneas by confocal scan. methods: thirty-one unscarred corneas from 22 patients with keratoconus, 24 clear corneas from 17 cases with post-lasik keratectasia, 12 corneas from 7 lasik cases without keratectasia, and 26 corneas from 13 normal subjects were evaluated using confocal scanning. none of the patients were contact lens wearers. keratocyte density was determined in three stromal layers and compared with densities in the corresponding layers in control corneas. cell densities in different corneal layers were also compared among the study groups. results: overall, 93 eyes from 59 patients with mean age of 30±7.3 years were evaluated. there was no difference in mean keratocyte density at 3 stromal layers between the keratoconus and control groups. in the post-lasik keratectasia group, keratocyte density was significantly lower than controls in the anterior and posterior stromal layers; whereas in lasik cases without keratectasia it was lower than controls in all 3 stromal layers. no difference in keratocyte density was found between cases with post-lasik keratectasia and lasik without keratectasia. in the post-lasik keratectasia group, there was a significant difference in keratocyte density between the anterior and posterior, and between the middle and posterior stromal layers; such a difference was not observed in the lasik cases without keratectasia. conclusion: mean keratocyte density seems to be lower in post-lasik keratectasia and lasik cases without keratectasia as compared to normal corneas. the distribution of keratocytes among different stromal layers was different in the two lasik groups: there was a non-homogenous distribution of keratocytes in stromal layers in the post-lasik keratectasia. whereas the distribution of keratocytes in the post-lasik cases without keratectasia was homogenous, this latter observation may be a protective factor against corneal ectasia.