Corneal Ectasia After Photorefractive Keratectomy: Case Series and Literature Review
Purpose
To analyze the risk factors associated with a series of ectasia cases following photorefractive keratectomy (PRK) and all such cases reported in the literature.
Methods
Retrospective analysis of post-PRK ectasia patients treated by us and all cases found in the literature. The 37 eyes included 8 eyes of 6 patients in our series and 29 eyes of 20 patients from the literature. Data included patient demographics; pre-operative data including best spectacle corrected visual acuity (BSCVA), manifest refraction, pachymetry and topography; perioperative and postoperative data including ablation depth, residual stromal bed (RSB), number of enhancement procedures, and the time to onset of ectasia. Risk scores for post-PRK ectasia were assessed using an established ectasia risk scoring system (ERSS) for laser in situ keratomileusis (LASIK) patients.
Results
Ectasia risk scores for age, RSB and spherical equivalent (SEQ) were zero in 70%, 87% and 78% of the eyes, respectively. Pachymetry risk score was 2 in 58% of the eyes and 3 or 4 in 16% of the eyes. Topography risk score was 3 in 46% of the eyes and 4 in 21% of the eyes. Cumulative ectasia risk score of 4 or greater (high risk) was found in 81% of the eyes.
Conclusion
Preoperative corneal topographic abnormalities and thin corneas are significant risk factors for the development of ectasia following PRK. Post-LASIK ectasia risk scoring by ERSS has some overlap with the risk for developing post-PRK ectasia.