Abstract
Purpose::
Optical coherence tomography (OCT) has been advocated as a tool for monitoring response to therapy in patients with neovascular age-related macular degeneration (AMD). Some have suggested that OCT parameters may correlate better with visual function changes than traditional imaging studies. In this study, we correlate measurements of retinal and subretinal layers on OCT with visual acuity.
Methods::
High-resolution radial line StratusOCT B-scans (set of six each) from 14 consecutive eyes with active neovascular AMD for whom protocol refracted visual acuities were available were selected. Cases were graded independently by certified reading center graders using a standard protocol and the custom OCT analysis software OCTOR, which allows the user to manually draw the boundaries of the layers to be quantified. Differences between graders were adjudicated to achieve a consensus reading. Specific layers quantified included: retina, outer nuclear layer (ONL) only, photoreceptor outer segments, subretinal fluid (SRF), subretinal tissue (SRT), and pigment epithelial detachments (PEDs). Volumes (mm3) of these structures were computed for the whole macula as well as for the foveal subfield alone and correlated with visual acuity (Pearson correlation).
Results::
A higher ONL layer volume showed a statistically significant correlation (R2 = 0.36) with better visual acuity (p=0.02 for total macula, p= 0.03 for central subfield). No other parameters including SRF volume and PED volume demonstrated a statistically significant correlation. SRT volume and retinal volume demonstrated a trend (p=0.11 for SRT, p= 0.09 for retina) for better acuity with higher volumes of retina and lower volumes of SRT, but the patients in this series generally did not have much retinal edema. The commonly used parameters from the StratusOCT output, including foveal center point thickness, foveal central subfield thickness, and total macular volume showed no statistically significant correlation.
Conclusions::
Various retinal layers and pathologic structures can be quantified by human graders using OCT analysis software. Measurements of these individual structures may correlate better with visual function than the limited measurements provided by the automated machine output.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • age-related macular degeneration • visual acuity