Choroidal and Outer Retinal OCT Features Preceding Development of Geographic Atrophy

Abstract

Purpose : To evaluate parameters based on optical coherence tomography (OCT) that may be predictive of progression to geographic atrophy (GA) secondary to age-related macular degeneration (AMD).

Methods : Retrospective review of SD-OCT imaging was conducted among subjects enrolled in ongoing studies of AMD. OCTs for subjects who progressed from intermediate AMD to GA (mean follow up: 2.8 years) after the baseline image (n=10), and age-matched subjects with no AMD (n=10) were assessed. One eye per subject was evaluated: the eye that progressed to GA, and the eye with the highest quality images for controls. OCT images at baseline, annually, and last exam prior to GA development were systematically evaluated to identify potential prognostic factors in the vitreo-retinal interface, retina, and choroid. An algorithm assessing the light-to-dark ratio (LDR) between choroidal stromal area and choroidal vessel lumen was calculated. OCT parameters for progressors and controls were compared using Fisher’s Exact and Welch’s t-test. Associations between OCT parameters and the LDR were also assessed.

Results : Among the choroidal features, irregularities in the choroidal vessels (thickening or thinning) were associated with progression to GA (P=0.02). Average sub-foveal choroidal thickness tended to be thinner in progressors compared to controls (188.4 μm vs. 272.2 μm, P=0.06). Choriocapillaris irregularity was significantly associated with the LDR (P=0.03). There was no difference in LDR between groups, suggesting that choroidal thinning associated with advanced AMD evolved with a preserved ratio between vessel lumen and choroidal stroma. Abnormal or disrupted outer neurosensory retinal parameters prior to signs of GA were noted for several features (P<0.0001): retinal thickness, external limiting membrane, ellipsoid zone, photoreceptor outer segments, and interdigitation zone.

Conclusions : This systematic analysis revealed that the outer retina was markedly affected prior to onset of GA. Additional abnormalities in outer neurosensory retina and retinal pigment epithelium also precede GA. Although there was a trend toward choroidal thinning, there was no difference in LDR.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Female, age 65. A) baseline fundus; B) follow-up at 3 years with GA (dashed line); C) baseline OCT with subsidence of outer plexiform layer (yellow arrow); D) baseline LDR; E) follow-up OCT at 3 years with GA overlying the site of the large vessels (white arrows)