In-vivo quantitative analysis of pterygium volume using anterior segment optical coherence tomography imaging

Abstract

Purpose : To propose a novel method for in-vivo quantitative analysis of pterygium volume using anterior segment optical coherence tomography (ASOCT) imaging.

Methods : ASOCT images of pterygia were obtained as part of a multicenter, prospective, randomized, double-masked, phase 2 study evaluating the safety, tolerability, and efficacy of topical AG-86893 in patients with pterygium (Allgenesis Biotherapeutics Australia Pty Ltd, Clinical Trial Number: NCT03533244). ASOCT was captured using the Heidelberg Spectralis ASOCT module (Heidelberg Engineering, Heidelberg, Germany) and a customized 41-line volume scan at high resolution mode, 15° (4.5 mm) OCT image section size, with enhanced depth imaging (Figure A). Pterygium boundaries were segmented using a modification of Duke OCT Retinal Analysis Program (DOCTRAP) which is a custom graphical user interface previously developed using MATLAB software (The Math Works, Inc., Natick, MA). For each B-scan, points along the upper and lower boundaries were manually marked by an experienced reader and interpolated using cubic interpolation. The manual segmentations were then projected to obtain an en face thickness map of the pterygium and the volume was calculated within the volume scan. This study is based on a preliminary analysis of the first 10 enrolled subjects.

Results : The upper boundary of pterygium was marked along and between the most anterior thin hyperreflective tear film layer and the most anterior hyporeflective conjunctival epithelium layer (white line on B-scan in Figure B). The lower boundary of pterygium was marked anterior and along the most posterior hyporeflective episcleral layer overlying the sclera which appears as a thick and well-defined band of hyperreflective tissue (purple line on B-scan in Figure B). Mean baseline pterygium volume was calculated as 2096823.20 ± 634748.39 pixel³.

Conclusions : We developed a novel method to analyze quantitatively pterygium volume using ASOCT imaging. This method may serve as an objective measure to evaluate the effect of topical agents to treat pterygia in future clinical trials.

This is a 2020 ARVO Annual Meeting abstract.

 

Figure. (A) ASOCT B-scan and near infrared image show OCT section passing through the cap, head, and body of the pterygium (Heidelberg Engineering, Heidelberg, Germany). (B) Same OCT B-scan image with segmentation lines marked manually with custom software.