Intrasession repeatability of swept-source OCT derived retinal thickness measurements in neovascular age related macular degeneration

Abstract

Purpose: Swept-source optical coherence tomography (SSOCT) imaging has recently been introduced into clinical practice but little is known about the repeatability of retinal thickness measurements in patients with neovascular age-related macular degeneration (AMD) using SSOCT imaging systems. The aim of this work was to determine the repeatability of retinal thickness measurements with a commercially available SSOCT device (DRI OCT-1; Topcon UK). The results of this work will lead to a better understanding of the magnitude of retinal thickness change needed using SSOCT to distinguish true clinical change from measurement variability. This in turn has implications for treatment algorithms for neovascular age-related macular degeneration using anti-angiogenic agents.

Methods: 42 eyes of 42 patients with known neovascular AMD were included in the study. Each patient underwent a 12 x 9mm raster scan using the DRI OCT-1. The scans were repeated three times in the same imaging session by a clinical trials certified technician. Retinal thicknesses were calculated for the 9 ETDRS (Early Treatment Diabetic Retinopathy Study) macular subfields using the onboard segmentation algorithm (TABS). Repeatability of measurements was assessed using coefficients of repeatability.

Results: There were 27 male and 15 female patients in the study with a mean age (± standard deviation) of 74.4 (±7.3) years and included 25 left and 17 right eyes. The coefficient of repeatability was 57µm for the central 1mm ETDRS (A1) subfield with a mean retinal thickness of 234µm (± 13.1 µm). Repeatability coefficients for other subfields ranged from 66µm to 33µm.

Conclusions: This study suggests that a change of >57µm in the central retinal subfield is highly indicative of true clinical change rather than measurement variability. This repeatability estimate of DRI OCT-1 based macular thickness change is of value when developing retreatment criteria for the use of anti-angiogenic agents in the treatment of neovascular AMD using commercially available SSOCT systems.