Demarcation Line in the Human Cornea After Surface Ablation Observed by Optical Coherence Tomography and Confocal Microscopy

Purpose: To investigate the long-term changes in anterior corneal structure after surface ablation. Methods: In this retrospective study, patients who received surface ablation including laser-assisted subepithelial keratomileusis (LASEK) and epipolis laser in situ keratomileusis at the Department of Ophthalmology of Fudan University Eye and Ear, Nose and Throat (EENT) Hospital (Shanghai, People's Republic of China) were telephoned. Patients were asked to follow-up at the refractive center. Changes in the anterior cornea (from the epithelium to the anterior stroma) were examined by optical coherence tomography (OCT) and in vivo confocal microscopy. Results: Thirty-four eyes of 18 patients (10 years or more after operation), 16 eyes of 8 patients (4 years after operation), 12 eyes of 6 patients (1 year after operation), 8 eyes of 4 patients (6 months after operation), and 12 eyes of 6 patients (1 month after operation) were included. Under OCT, a smooth, continuous, and highly reflective demarcation line between the epithelial layer and the stroma was noted in all eyes that received surgeries more than 1 year previously. For eyes at 6 months after operation, the complete formation of this demarcation line was detected in 12.5% (1/8) of eyes and a partial formation of this demarcation line was observed in 87.5% (7/8) of eyes. A partial formation of this demarcation line was observed in 100% (12/12) of eyes in patients at 1 month after surgery. Conclusions: A demarcation line in the human cornea can be detected after corneal surface ablation. It was completely formed around postoperative 6 to 12 months. The functions and components of this structure merit investigation.