Post-LASIK Ectasia versus Keratoconus: An in Vivo Confocal Microscopy Study
Azam Alvani1 , Hassan Hashemi1 *, Mohammad Pakravan2 , Mirgholamreza Mahbod1 , Mohammad Amin Seyedian1 , Kazem Amanzadeh1 , Mehdi Khabazkhoob1 , Ebrahim Jafarzadehpur3 , Akbar Fotouhi4
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
- Ophthalmic Epidemiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
- Department of Optometry, School of Rehabilitation, Iran University of Medical Sciences, Tehran, Iran.
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Abstract: To examine and compare corneal cellular and subbasal nerve (SBN) characteristics in post laser-assisted in situ keratomileusis (LASIK) ectasia (PLE), normal post-LASIK corneas (PLC), keratoconus (KC), and normal virgin corneas (NC).
Methods: In this cross-sectional comparative study, 18 PLE eyes of 11 patients, 18 PLC of 15 cases, 32 KC eyes of 32 patients, and 29 NC of 29 subjects were assessed using in vivo confocal microscopy. The density of the basal epithelial cell (BEC), anterior keratocyte, posterior keratocyte, and endothelial cell layers, as well as the characteristics of SBN fibers were compared between the four groups.
Results: The density of the BEC, and the anterior and posterior keratocyte layers were significantly lower in KC compared to NC (-650±190, P=0.013; -181±39, P˂0.001; -36±11, P=0.021, respectively). However, there was no significant difference between PLE and PLC regarding these parameters (all P≥0.6). Mean SBN parameters including central corneal nerve branch density, nerve fiber length, total branch density, and nerve fiber area were significantly lower in KC compared to NC, and in PLE compared to PLC (all P≤0.021).
Conclusion: The pathophysiology of PLE seems to differ from KC. Apparent changes in BEC, and anterior and posterior keratocytes associated with KC were not observed in PLE. However, SBNs appear to be involved in both conditions.
