Purpose
Geographic atrophy (GA) in Stargardt disease (STGD) results from the abnormal accumulation of A2E in photoreceptors, which subsequently causes loss of the retinal pigment epithelium (RPE), photoreceptors, and choriocapillaris. In age-related macular degeneration (AMD), the primary cause of GA is not known. If the presence of GA affects the underlying choroidal thickness (CT), then we might expect eyes with similar amounts of GA, regardless of etiology, to have similar CT measurements. If there’s a difference in the CT measurements underlying GA in AMD and STGD, then this difference might reflect a difference in the underlying pathophysiology leading to GA. To determine if different diseases causing GA have a similar or different affect on subfoveal CT measurements, we compared measurements from eyes with similar areas of GA secondary to AMD and STGD.
Methods
Patients with the diagnosis of central GA secondary to STGD and AMD were enrolled in a prospective spectral domain optical coherence tomography imaging study. Subfoveal CT was measured from the central B-scan using an enhanced depth imaging protocol. The area of GA was measured using fundus autofluorescence imaging. Two independent graders measured the subfoveal CT and areas of GA. AMD eyes were divided into those with and without reticular pseudodrusen. CT from all group were compared.
Results
A total of 22 eyes of 22 patients were included in the STGD group and in the AMD group, and these eyes were matched with respect to the area of GA. The mean age of the STGD patients was 48.9 (SD 17.1) and 81.8 (SD 6.2) for the AMD patients. Mean area measurements of GA for the STGD and AMD groups were 5.4mm2 (SD 4.1) and 5.1 mm2 (SD 4.0), respectively (P=0.83). After adjusting for age, eyes with STGD had a mean CT measurement greater than the AMD eyes (336.1 vs.198.1µm respectively; p=0.039). But this difference seemed to be driven by AMD eyes with reticular pseudodrusen (RPD) and a single Stargardt case with a very thick choroid. Eyes with RPD had statistically thinner choroids when compared to all other groups.
Conclusions
No clinically meaningful difference was observed between the CT in normal eyes and eyes with STGD and AMD without RPD containing similar areas of GA. However, eyes with GA and RPD had significantly thinner subfoveal CT.