Official ESCRS | European Society of Cataract & Refractive Surgeons


Bowman’s layer topography: comparing virtual values vs manual measurement

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Session Details

Session Title: Anterior Segment Imaging

Session Date/Time: Monday 16/09/2019 | 14:00-16:00

Paper Time: 15:18

Venue: Free Paper Forum: Podium 4

First Author: : P.Paritekar INDIA

Co Author(s): :    R. Shetty   A. Sinha Roy   C. Rachana   G. Kundu                    

Abstract Details


To describe a novel method of computing topography of the corneal surface and Bowman’s Surface using Anterior Segment – Optical Coherence Tomography (AS-OCT) and comparing this with Bowman’s layer topography measured after epithelium removal


Tertiary eye care institute in Bangalore, India


25 normal and 25 Keratoconus(KC) eyes were analyzed using undistorted AS-OCT ( Optovue Inc.) and Pentacam HR. Curvatures for OCT was calculated from the detected Anterior corneal surface (ACS) and Bowman’surface on the 8 radial scans. Similarly, curvatures of the same ACS were obtained from Pentacam (OCULUS Optikgerate Gmbh, Germany). Manual epithelium removal of normal eyes during photorefractive keratectomy and KC eyes during cross linking was performed by a single surgeon and topography was repeated intraoperatively (intra-op) to manually measure Bowman’s topography. Intraclass Correlation Coefficient(ICC) and Coefficient of Variation(CoV) were performed


The ICC of mean K1, K2 and Kmax (D) was high (0.96, 0.83 and 0.94) between Bowman's surface measured intra-operatively (44.74 ± 0.52 , 42.38 ± 0.39 and 45.33 ± 0.45) and derived from pre-op images (44.14 ± 0.52 , 41.55 ± 0.42 , 44.42 ± 0.54), respectively. In KC patients, the ICC of mean K1, K2 and Kmax(D) of Bowman’s surface measured intra-operatively (57.89 ± 1.18, 50.13 ± 0.86 and 59.27 ± 1.24 ) and derived from pre-op virtual images (58.25 ± 1.27 , 49.79 ± 0.86 and 59.68 ± 1.33) was excellent (0.98, 0.96 and 0.99 respectively)


This study presents a novel, non-invasive method for “virtual de-epithelization” using OCT, where no physical removal of epithelium is required. This tool can be useful for preoperative screening, monitoring the progression and stability, customized crosslinking, planning of trans-epithelial procedures and topography guided LASIK

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