Measuring progression at the edge of dense macular scotomas in Stargardt disease

Abstract

Purpose : As new treatments such as pharmacotherapy, gene or stem cell therapy for Stargardt disease enter clinical trials, functional surrogate outcome measures are needed. We previously demonstrated that microperimetric mean sensitivity (MS) derived from a standard test grid using microperimetry is a sensitive outcome measure. Here, we hypothesize that the functional decline is faster at the edge of the dense scotoma (eMS) than using MS.

Methods : As part of the international, multicenter, prospective ProgStar study (NCT01977846), patients with molecularly confirmed Stargardt disease (at least one mutation in ABCA4) were followed over 24 months in 6-monthly intervals using the Nidek MP-1 and a custom Humphrey 10-2 test grid with 68 test locations. Custom software was used to automatically identify and selectively follow the points directly adjacent to dense scotoma points (defined as unable to see the brightest light stimulus at baseline) and to calculate their mean sensitivity (eMS). Manual grading of eMS was performed to validate the method.

Results : A total of 361 eyes (185 patients) were included into the analysis (mean age 32.9 ± 15.1; 46% male). At baseline, MS was 10.4 ± 5.2 dB (N=361) and the eMS was 9.3 ± 3.3 dB (N=335). The yearly progression rate of MS (1.5 ± 2.1 dB/yr) was statistically significantly lower (β = -1.33, p < .001) than for eMS (2.9 ± 2.9 dB/yr). eMS did not differ between automated and manual grading (β = .09, p = .461).

Conclusions : In Stargardt disease, macular sensitivity declines significantly faster at the edge of the dense scotoma than in the overall test grid. An automated, time-efficient approach for extracting and grading eMS is possible and appears valid. Thus, eMS offers a valuable tool and sensitive outcome measure to follow STGD1 in clinical trials, allowing clinical trial designs with shorter duration and/or smaller cohorts.

This is a 2020 ARVO Annual Meeting abstract.

 

Progression of microperimetric mean sensitivity derived from a standard test grid using microperimetry over 12 months (MS in dB top left) in the left eye of a patient with molecularly confirmed Stargardt disease type 1. Points in the edge of the dense scotoma are overlaid in light blue. Custom software automatically identified these test locations and calculated the average sensitivity in these locations (eMS in dB, indicated in the top right).