Abstract
Purpose: :
To determine the correlation between photoreceptor thickness and visual acuity in patients with dry AMD using high speed, ultrahigh resolution OCT.
Methods: :
Forty-one eyes from 41 patients diagnosed with dry AMD were scanned using a high speed, ultrahigh resolution OCT (UHR OCT) prototype instrument with a 3 um axial resolution at ~26,000 axial scans/second. Three high-definition images, each 6mm long and with 8192 axial scans, were acquired from the central fovea to confirm the clinical diagnosis of dry AMD. A 3-D scan protocol, which acquires 180 images of 512 axial scans each, in a 6 x 6 mm region centered on the fovea, was also performed. The five central most images were then extracted for measurement. Lines representing central foveal thickness (CFT) and foveal outer segment pigment epithelium thickness (FOSPET) were manually drawn and measured. CFT was measured from the vitreoretinal interface to the posterior surface of the RPE. In the same location, FOSPET was measured from the anterior surface of the IS/OS junction to the posterior surface of the RPE. Pearson correlations and linear regressions were calculated between: 1) CFT and logMAR 2) FOSPET and logMAR, 3) logMAR and the difference of FOSPET from CFT, and 4) CFT and FOSPET.
Results: :
Patients with poor visual acuity had correspondingly disrupted or atrophied retinal pigment epithelium and thinned or compressed IS/OS layer. There was a moderate correlation between CFT and visual acuity (r = -0.442, p = 3.8x10-3) and an even stronger correlation between FOSPET and visual acuity (r = -0.605, p = 2.79x10-5). Additionally, there was strong correlation between CFT and FOSPET (r = 0.617, p = 1.73x10-5). No correlation was found between visual acuity and the difference of FOSPET from CFT (r = -0.148, p = 0.355).
Conclusions: :
High speed, UHR OCT enables delineation of the photoreceptor outer segments for both qualitative and quantitative analysis of dry AMD. The FOSPET measurement may be a promising and more objective method of monitoring dry AMD to assess disease progression and guide treatment decisions.
Keywords: age-related macular degeneration • photoreceptors • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)