Purpose
In Stargardt disease, unlike geographic atrophy from AMD, the dense scotoma often far exceeds the size of the atrophic lesion on fundus autofluorescence, fluorescein angiography, or color fundus photos. For this reason, microperimetry is necessary for determining the size of dense scotoma and its enlargement over time. With a growing interest in potential treatments for Stargardt disease, it is important to better understand the natural history of the disorder and the optimal ways of quantifying this. We mapped the dense scotoma over time in a group of Stargardt patients and present the findings here.
Methods
We retrospectively reviewed patients with Stargardt disease who had testing that fully defined their dense scotomas (Goldmann III stimulus) with the Nidek MP-1 on at least two visits. Twelve patients had extensive mapping of the dense scotoma; seven mapped the full boundary of the scotoma so that an enlargement rate could be determined. Median follow-up was 4.5 years (range 1.5 to 8.0), and median number of testing sessions was 3 (range 2-5).
Results
The mean rate of enlargement of the dense scotoma was 1.37 mm2 per year (std dev 1.08). The two eyes of each patient were highly concordant in the rates of enlargement, with mean absolute difference between eyes of 0.26 mm2 per year, and correlation of 0.95. Baseline areas were less highly correlated (correlation 0.66). Four patients had age of onset between 6 and 13, and three between 23 and 40. Time from onset did not differ between groups. The younger group had worse acuity and a trend to more rapid enlargement. The mean time required for dense scotoma mapping was 5.3 minutes per eye, with no eye requiring more than 10 minutes.
Conclusions
Dense scotomas continue to enlarge over time in Stargardt disease. There is strong correlation in enlargement rate between eyes, so that the fellow eyes could serve as a comparison group in uniocular treatments. In all these cases, the borders of the dense scotoma could not be predicted based on the fundus image.