Performance of a Novel OCT Segmentation Method for Determining Lesion Volume in the Assessment of a Non-Human Primate Model of Choroidal Neovascularization

Abstract

Purpose : To compare the performance of a novel OCT segmentation method for determining lesion volume and fluorescein angiography (FA) in the assessment of eyes of non-human primates (NHP) with experimental CNV treated with intravitreal (IVT) Lucentis™ and those receiving IVT saline control.

Methods : Twenty eyes of 10 cynomolgus macaques with laser-induced CNV (9 laser areas/macula) were monitored using OCT and FA at 2- and 4-week time points following CNV induction. Ten eyes (5 animals) were treated with IVT Lucentis 2 days after the 2-week time point (LUC); the other 10 eyes (5 animals) were treated with IVT PBS (CTR). OCT volume scans were converted to DICOM format and 3 tissue boundaries were segmented using semi-automated software (EdgeSelect™; EyeKor, Inc.) including: the Inner Limiting Membrane (ILM), Bruch’s Membrane (BM), and the internal border of CNV lesions. Segmentation analyses were used to calculate the volumes of the CNV laser lesions (from the internal lesion border to BM), and total retinal volume (TRV; from ILM to internal lesion border). FA was scored using a semi-quantitative system to assign a leakage severity score (1-4) to each laser lesion.

Results : Three LUC eyes and 1 CTR eye were excluded after laser induction due to subretinal hemorrhage. Over the 2-4 week interval following induction, there was no significant difference (p=0.626) in mean % change in CNV volume in the 7 remaining LUC eyes (-41.002% ± 6.976) and the 9 remaining CTR eyes (-36.231% ± 6.510). There was a slightly significant difference (p=0.043) in mean % change in TRV between LUC eyes (-4.651% ± 0.946) and CTR eyes (-1.552% ± 0.978). During the same interval, the number of Grade 4 lesions on FA decreased by 100% in LUC eyes and 63% in CTR eyes.

Conclusions : OCT-derived CNV lesion volume measurements can provide valuable quantification data for structural retinal changes and generally correlate with FA leakage and change over time in untreated NHPs with laser-induced CNV. However, they are not necessarily superior to FA in predicting response to anti-VEGF treatment in this model. This may be due to higher amounts of subretinal fibrosis in laser-induced CNV lesions, yielding a discrepancy in OCT volume and FA leakage. CNV volume may be a more useful clinical endpoint to follow if treatment is administered at an earlier stage in the lesion development.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.