Reproducibility of Quantitative Optical Coherence Tomography Sub-Analysis in Neovascular Age-Related Macular Degeneration

Abstract

Purpose:: To determine the reproducibility of computer-assisted grading and quantification of retinal structures on optical coherence tomography (OCT) images from eyes with neovascular age-related macular degeneration (AMD).

Methods:: Sixty OCT image sets (set of six each) from eyes with neovascular AMD were independently analyzed by two certified reading center graders and compared. Custom software (termed OCTOR) was used to manually define the borders of the retina and other relevant structures on each radial-line scan, and compute thicknesses and volumes analogous to conventional StratusOCT software (including measurements of the 9 standard ETDRS macular subfields, total macula, and the foveal center point, FCP). Boundaries delineated included: the inner and outer retinal surface, inner and outer surface of any tissue in the subretinal space, inner surface of the retinal pigment epithelium (RPE), and estimated original location of the RPE in cases with RPE detachments (PEDs). Defining these boundaries allowed quantification of the following sub-spaces: retina, subretinal fluid, subretinal tissue, and PEDs. Correlation coefficients, mean differences (MD), and kappa statistics were calculated.

Results:: Comparison of the FCP thicknesses, central subfield volumes, and total macular volumes for the various spaces showed a high level of correlation (R² ≥ 0.88 and Κ ≥ 0.72 for all parameters). Of the various FCP thicknesses (for retina, subretinal fluid, subretinal tissue, PED), the retina had the highest correlation between graders (R² = 0.97, Κ = 0.84, MD = 18 µm) and subretinal tissue had the lowest (R² = 0.94, Κ = 0.72, MD = 17 µm). For central foveal subfield volume, the highest correlation was for the retina (R² = 0.97) and the lowest was for subretinal fluid (R² = 0.95). For total macular volume, the retina had the highest correlation (R² = 0.94, Κ = 0.82, MD = 0.23 mm³) and subretinal tissue had the lowest (R² = 0.88, Κ = 0.73, MD = 0.13 mm³).

Conclusions:: Analysis of OCT images using computer-assisted grading software allows for highly reproducible measurements of the retina, subretinal fluid, subretinal tissue, and PEDs in eyes with complex pathologies such as neovascular AMD. Such quantitative sub-analysis may be useful in evaluating and quantifying the response to therapeutic interventions.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • retina