OCT-Angiography Quantification of Peripapillary Retinal Vessel Density In Myopes with and Without Tilted Discs and Emmetropes

Abstract

Purpose : To examine the effect of myopia and optic disc tilt on peripapillary perfused vessel density (PVD) as measured by optical coherence tomography angiography (OCTA). High myopia and tilted optic discs may be associated with visual field defects presumed secondary to mechanical stress on optic nerve fibers. Peripapillary retinal perfusion may play a role. This study is the first to investigate the effect of myopia and optic disc tilt on peripapillary PVD as measured by OCTA

Methods : Emmetropic control and myopic (myopia ≥ -1.0 D) eyes were imaged using the Optovue Avanti XR OCT system™ (Fremont, CA) to obtain OCT volumetric images of the optic disc (4.5 mm x 4.5 mm) The Split-Spectrum Amplitude Decorrelation AngiographyTM (SSADA) was used to create a 3-dimensional map of perfused vessels in the peripapillary retinal nerve fiber layer (RNFL). The Optovue AngioAnalytics softwareTM was used to calculate the PVD as the percent area of perfused vasculature within the RNFL divided into six peripapillary segments and one inside disc segment. A custom algorithm was used to generate a color-coded density map of perfused radial peripapillary vessels. Average perfusion density values in emmetropes vs. myopes were compared in the peripapillary segments. Statistical analysis was performed in SPSS Software © (Version 24, IBM Corporation, Armonk, NY), Student t-tests were used to compare group differences in PVD; a multiple regression model was used to quantify the variance accounted for by disc tilt and refractive error.

Results : PVD in 36 emmetropic and 28 myopic eyes (6 with tilted discs) were analyzed. Myopic eyes demonstrated lower PVD in overall peripapillary ring, nasal, temporal, and inferotemporal sectors. The inside disc sector of myopic eyes demonstrated significantly higher PVD than emmetropic eyes. Multiple regression analysis found that disc tilt, and not refractive error, predicted variance of PVD in the peripapillary, nasal, and inside disc sectors

Conclusions : Myopic eyes have statistically significant decreases in peripapillary PVD compared with emmetropic eyes, as measured by OCTA. The presence of optic disc tilt may be more predictive of decreased PVD than myopic refractive status alone.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.