Purpose:
Stargardt disease is primarily a disease of the photoreceptors followed by RPE loss and formation of geographic atrophy (GA). In AMD, the primary cause of GA is not known, but these eyes with GA have thinner choroids than in normal eyes. If the loss of choroidal thickness is the direct result of photoreceptor and RPE loss, then we would expect similar choroidal thickness measurements in eyes with Stargardt disease and AMD once adjusted for age, axial length, and the extent of GA. To test this hypothesis, we compared choroidal thickness measurements in eyes with Stargardt disease and AMD.
Methods:
Patients with the diagnosis of GA secondary to Stargardt disease and AMD were enrolled in a prospective SDOCT imaging study. SDOCT imaging was performed using the Cirrus (Carl Zeiss Meditec, Inc.) and the Spectralis (Heidelberg, Heidelberg, Germany) instruments. The area of GA was measured on the OCT fundus image generated using the Cirrus scan pattern of 200x200 A-scans. Subfoveal choroidal thickness was measured from the central B-scan using the Spectralis enhanced depth imaging protocol. Two independent graders measured the subfoveal choroidal thickness. Axial length was measured using the IOL Master (Carl Zeiss Meditec Inc., Dublin, CA). Multiple linear regressions were used to compare choroidal thickness measurements after adjusting for age and axial length.
Results:
A total of 16 eyes of 8 patients were included in the Stargardt group and 16 eyes of 16 patients with AMD were included and matched with respect to the area of GA. Mean area of GA was 4.68 mm2 (SD=4.5) and 4.69 mm2 (SD=4.1) for the Stargardt and AMD groups, respectively. The mean age of the Stargardt patients was 29.5 (SD=10.0) and 81.0 (SD=7.4) for the AMD patients. Mean subfoveal choroidal thickness was 327.9 µm (SD=70.7) for the Stargardt eyes and 201.5 (SD=137.3) for the AMD eyes. Mean axial length was 23.8 mm (SD=0.93) for the Stargardt patients and 23.5 mm (SD=1.09) for the AMD patients.
Conclusions:
AMD eyes with GA have thinner choroids than Stargardt eyes with GA suggesting that the thinner choroid in AMD eyes is associated with the primary cause of the disease rather than a response to photoreceptor and RPE loss.
Keywords: age-related macular degeneration • choroid • retina