Ectasia after keratorefractive surgery: Analysis of risk factors and treatment outcomes in the Indian population

Abstract

Purpose: To analyze the risk factors in eyes developing ectasia following keratorefractive procedures. In addition, the study assessed visual outcomes following various treatment modalities for ectasia. Methods: In this retrospective study, data of patients who underwent keratorefractive procedures, presenting to the refractive services of a tertiary eye care hospital in South India between January 2016 and May 2019 was analyzed. Of these, the eyes that developed ectasia were noted and the possible risk factors were determined. Visual outcomes following treatment with corneal collagen crosslinking (CXL) with or without intracorneal ring segment implantation (ICRS) or topography-guided corneal ablation (T-PRK) were analyzed. Results: Forty eyes of 26 patients developed ectasia following keratorefractive procedures, with a mean interval of 73.1± 45.4 months between primary procedure and ectasia development. Of these, 14 patients had bilateral presentation. Identifiable risk factors included ablation depth >75 μm (59.25%), percentage of tissue altered (PTA) >40% (48.14%), residual stromal bed <300 μm (22.22%), mean refractive spherical equivalent >8 D (25.92%), inferior–superior (I–S) asymmetry >1.4D (7.40%), central corneal thickness (CCT) <500 μm (7.40%), Belin Ambrosio Display (BAD) >2.5 (7.40%), posterior float elevation maximum ≥18 μm (3.70%), and pellucid marginal degeneration (PMD; 3.70%). Conclusion: Our study shows that only 70% of the eyes demonstrated an identifiable risk factor for the development of ectasia. Ablation depth of >75 μm and the PTA >40% were the most common risk factors. Treatment following CXL with ICRS or T-PRK demonstrated significantly better visual outcomes in comparison with CXL alone.

Alternative indications for corneal crosslinking

“…Treatment with CXL was found to be more effective in achieving keratometry flattening, corneal regularization, and reduction in spherical equivalent when additional PRK or intrastromal corneal ring segment implantation was added. 45…”

“…As the diagnosis of postrefractive surgery is only made after a mean of more than 6 years, 126 these shorter studies are not able to reflect the true patient population. 45 Patients with radial keratotomy often complain of fluctuating vision during the day. The interesting hypothesis that CXL could stabilize these fluctuations has been confirmed only in 3 case reports.…”

“…As the diagnosis of postrefractive surgery is only made after a mean of more than 6 years, 126 these shorter studies are not able to reflect the true patient population. 45…”