Changes In Corneal Thickness And Curvature Following Inlay Implantation

Abstract

Purpose: : To study the changes in total corneal and eptithelial thickness as well as changes in curvature for inlay implanted corneas by comparing results obtained from Orbscan IIz instrument and Optovue OCT images.

Methods: : Four unsighted eyes of four human subjects were implanted with corneal inlays. Cross-sectional OCT scans using Optovue and topography maps using Orbscan IIz were taken at 6 timepoints from pre-operative up to Month 3 post-operative. Thicknesses of different corneal layers were measured separately using their corresponding refractive index and customized software to analyze the OCT images. Thickness profiles of the cornea across 6 mm diameter range were calculated. Anterior and posterior cornea radii of curvatures were determined from the OCT images and compared to values obtained from Orbscan IIz instrument.

Results: : Average corneal thickness at pupil center had increased by (mean ± STDEV) 61 ± 16 µm at Day 1 post-operative and progressively decreased to 34 ± 8 µm at Month 3 post-operative. The average corneal flap and inlay thickness measured at pupil center was consistent across all post operative time points of 166 ± 4 µm and 38 ± 1 µm respectively. There were significant gradual thinning in epithelial thickness up to 30 % by Month 3 post-operative. Anterior curvature of the cornea and the epithelium significantly steepened by an average of 0.35 mm and 0.31 mm respectively at Month 3 post-operative. No siginificant changes in the posterior corneal curvature. Anterior corneal curvature values obtained from the Orbscan IIz instrument measured was significantly steeper at all post-operative timepoints than curvature values obtained using OCT images and customized software.

Conclusions: : Post corneal inlay implantation changes in the corneal thickness and curvature where observed and measured. There were increase in corneal thickness above the added inlay thickness but this dissipated by Month 3 post-operative. This transient change was likely attributed to post-operative swelling. Epithelial thinning was present in all eyes post implantation. Anterior curvature of the cornea significantly steepened as a result of the positive powered inlay while posterior curvature change was not significant. Orbscan IIz instrument measured steeper anterior curvature values and somewhat flatter posterior curvature values.

Keywords: cornea: basic science • imaging/image analysis: non-clinical • refractive surgery