How is light sensitivity of the posterior pole compromised in Stargardt disease?
In this multicenter prospective cohort study, microperimetric mean sensitivity was lower in the fovea than in the peripheral macula. Overall mean sensitivity was lower in older patients and those stating longer disease duration. There are cases with obvious discrepancies of low mean sensitivity measurements with good visual acuity; these cases showed foveal sparing on fundus autofluorescence testing.
These findings suggest microperimetry allows a more comprehensive assessment of the function of the central retina, and it may serve as an outcome measure in future clinical trials for Stargardt disease and other macular diseases.
New outcome measures for treatment trials for Stargardt disease type 1 (STGD1) and other macular diseases are needed. Microperimetry allows mapping of light sensitivity of the macula and provides topographic information on visual function beyond visual acuity.
To measure and analyze retinal light sensitivity of the macula in STGD1 using fundus-controlled perimetry (microperimetry).
Design, Setting, and Participants
This was a multicenter prospective cohort study. A total of 199 patients and 326 eyes with molecularly confirmed (ABCA4) STGD1 underwent testing with the Nidek MP-1 microperimeter as part of the multicenter, prospective Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study. Sensitivity of 68 retinal loci was tested, and the mean sensitivity (MS) was determined; each point was categorized as “normal,” “relative,” or “deep” scotoma.
Main Outcomes and Measures
Mean sensitivity and the number of points with normal sensitivity, relative, or deep scotomas.
Mean (SD) patient age was 34.2 (14.7) years, mean (SD) best-corrected visual acuity of all eyes was 47.8 (16.9) Early Treatment Diabetic Retinopathy Study letter score (approximately 20/100 Snellen equivalent), and mean MS of all eyes of all 68 points was 11.0 (5.0) dB. The median number of normal points per eye was 49 (mean [SD], 41.3 [20.8]; range, 0-68); abnormal sensitivity and deep scotomas were more prevalent in the central macula. Mean sensitivity was lower in the fovea (mean [SD], 2.7 [4.4] dB) than in the inner (mean [SD], 6.8 [5.8] dB) and outer ring (mean [SD], 12.7 [5.3] dB). Overall MS per eye was 0.086 dB lower per year of additional age (95% CI, −0.13 to −0.041; P < .001) and 0.21 dB lower per additional year of duration of STGD1 (95% CI, −0.28 to −0.14; P < .001). Longer duration of STGD1 was associated with worse MS (β = −0.18; P < .001), with a lower number of normal test points (β = −0.71; P < .001), and with a higher number of deep scotoma points (β = −0.70; P < .001). We found 11 eyes with low MS (<6 dB) but very good best-corrected visual acuity of at least 72 Early Treatment Diabetic Retinopathy Study letter score (20/40 Snellen equivalent).
Conclusions and Relevance
We provide an extensive analysis of macular sensitivity parameters in STGD1 and demonstrate their association with demographic characteristics and vision. These data suggest microperimetry testing provides a more comprehensive assessment of retinal function and will be an important outcome measure in future clinical trials.
Schönbach EM, Wolfson Y, Strauss RW, Ibrahim MA, Kong X, Muñoz B, Birch DG, Cideciyan AV, Hahn G, Nittala M, Sunness JS, Sadda SR, West SK, Scholl HPN, for the ProgStar Study Group. Macular Sensitivity Measured With Microperimetry in Stargardt Disease in the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) StudyReport No. 7. JAMA Ophthalmol. Published online May 25, 2017. doi:10.1001/jamaophthalmol.2017.1162