Abstract
Purpose: :
To determine if detailed measurements of outer retinal layers in spectral domain OCT (SD-OCT) scans passing through the foveola correlate with Snellen visual acuity.
Methods: :
A retrospective analysis of volume SD-OCT scans was performed on a consecutive series of patients with various macular diseases from a retina specialty clinic imaged either on 3D-OCT-1000 (Topcon Corporation, Tokyo, Japan) or Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany). Best or pinhole visual acuities were collected from clinic charts. A single horizontal B-scan deemed to be closest to the foveal center in each volume SD-OCT image set was selected using standardized criteria and loaded into Photoshop (ver. CS3, Adobe, Inc). Boundaries representing the inner limiting membrane (ILM), the external limiting membrane (ELM), the IS/OS junction, the outer limit of the photoreceptors (POS), and the inner and outer RPE boundaries were graded by two graders. Thicknesses and average intensities for the photoreceptor inner and outer segments, the entire photoreceptors, and all trained boundaries were calculated using custom software and correlated with Snellen visual acuity.
Results: :
131 eyes of 100 patients scanned on 3D-OCT-1000 and 87 eyes of 54 patients scanned on Spectralis HRA+OCT were included. The thickness of the photoreceptor inner segments correlated more strongly with visual acuity than the outer segment, total photoreceptor or total retinal thicknesses (Table 1). Inner segment and photoreceptor intensities also correlated with visual acuity. The degree of correlation was quite similar between the two instruments and remained relatively unchanged after the datasets were combined.
Conclusions: :
In this study, the average thickness and intensity of the photoreceptor inner segments correlated better with visual acuity than other thickness or intensity measurements. Objective measurements such as these may be useful adjunctive measures in clinical trials guided by functional outcomes.
Keywords: visual acuity • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical