En Face Imaging of the Choroid in Diabetic Retinopathy using Swept-Source Optical Coherence Tomography

Abstract

Purpose: To define the choroidal layers in eyes with diabetic retinopathy (DR) using en face images from swept-source optical coherence tomography (SS-OCT).

Methods: Diabetic and age-matched normal subjects were prospectively scanned with a prototype SS-OCT system obtaining 100,000 A-lines/sec at a wavelength of 1050nm and axial resolution of 6 µm. A motion correction algorithm was applied to merge the 12x12 mm scans into a single volumetric dataset. Scans were flattened using the RPE/Bruch's membrane complex as a reference, to facilitate en face image generation at an interval of 4.13 µm (1 pixel) starting from the RPE. Choroidal layers were qualitatively and quantitatively characterized.

Results: Thirty seven eyes from 27 subjects with DR were enrolled; 22 eyes had non-proliferative DR and 15 eyes had proliferative DR; Best corrected visual acuity (BCVA) ranged from 20/20 to 20/200. Twenty two eyes from 13 normal subjects were enrolled with BCVA of 20/20 or better. Systemic analysis of en face SS-OCT images was used to define the choriocapillaris (CC), inner choroid (IC), and outer choroid (OC). In the DR group, the mean thickness ± standard deviation (SD) of each layer was: CC (40.4 ± 11.0 µm), IC (43.6 ±19.7 µm), and OC (205.0 ± 45.9 µm). In the normal group, the mean thickness ± SD of each layer was: CC (64.2 ± 23.9 µm), IC (67.4µm ± 22.2 µm), and OC (233.9 ± 5.2 µm). CC and IC were significantly thinner in the diabetic group when compared to the normal group (p < 0.001). In the DR group, the mean proportion of each layer of the total choroidal thickness was: CC 14%, IC 15%, and OC 71%. In the normal group, the mean proportion of each layer was: CC 18%, IC 18%, and OC 64%. The CC and IC contributions to the total choroidal thickness were significantly less in the diabetic eyes when compared to the normal eyes (p= 0.007, p= 0.009, respectively). The OC contribution to the total choroidal thickness was significantly higher in the diabetic eyes when compared to normal eyes (p< 0.001).

Conclusions: DR eyes had thinner choroids when compared to normal eyes. CC and IC contributed less to the total choroidal thickness in DR when compared to normal subjects. En face SS-OCT might provide a useful tool to better understand the pathophysiology of diabetic choroidopathy.

Keywords: 452 choroid • 499 diabetic retinopathy • 550 imaging/image analysis: clinical