Identifying Subtle Cues In Collagen Alignment In Post-Lasik Ectasia By Polarization-Sensitive Optical Coherence Tomography (Ps-Oct)

Published 2022 - 40th Congress of the ESCRS

Reference: PP05.06 | Type: ESCRS 2022 - Posters | DOI: 10.82333/xhks-ky72

Authors: Sailie Shirodkar* ¹ , Rohit Shetty ² , Pooja Khamar ¹ , Raghav N ³ , Rahul Patil ³ , Abhijit Sinha Roy ³

¹Cataract and Refractive Services,Narayana Nethralaya, Bangalore,Bangalore,India, ²Cornea and Refractive Services,Narayana Nethralaya, Bangalore,Bangalore,India, ³Imaging, Biomechanics and Mathematical Modeling solutions (IBMS) Lab,Narayana Nethralaya, Bangalore,Bangalore,India

Purpose

To study the changes in collagen fibril structures in post-LASIK ectasia (PLE) and healthy post-LASIK corneas eyes using custom-built ultrahigh resolution polarization sensitive optical coherence tomography (PS-OCT).

Setting

Narayana Nethralaya Superspeciality Eye Hospital, Bangalore, India

Methods

35 PLE eyes, 50 healthy post-LASIK eyes and 50 normal (unoperated) eyes were imaged using ultrahigh resolution PSOCT to analyse the collagen fibril structure in the stroma. A scan field of 11mm diameter was achieved using conical scan setup enabling uniform signal strength throughout the cornea. Phase retardation (PR) enface maps were generated at the posterior corneal surface. Zonal analysis was performed on the PR enface maps in annular zones from centre to periphery.

Results

PR enface maps of the unoperated healthy eyes showed the preferential arrangement of collagen fibrils with least retardation in the apex and anchoring fibrils in periphery. Healthy post-LASIK eyes had PR distribution similar to normal (unoperated) eyes. Few post-LASIK eyes showed very healthy PR distribution with intact anchoring fibrils even after 6 years post-surgery. PLE eyes showed abrupt changes in PR as compared to healthy post-LASIK eyes (p<0.03). Zonal analyses of PR values showed higher retardation in PLE eyes in regions of higher curvatures.

Conclusions

Significant disruption in corneal fibrillar arrangement was seen in PLE corneas, possibly indicating loss of corneal integrity. PR enfaces maps derived from PS-OCT can be used to track changes in collagen fibril arrangement in post-refractive surgeries aiding in early ectasia detection. PS-OCT can clinically help in identifying corneas with abnormal morphology/fibrillar arrangement prior to the surgery, which could be overlooked otherwise.