Purpose
To characterize macular function with MP1 and its association with visual acuity (VA) in the ProgSTAR study (The Natural History of the Progression of Geographic Atrophy Secondary to Stargardt Disease).
Methods
Patients with ≥2 pathogenic mutations (PM) in the ABCA4 gene or 1 PM with a typical STGD phenotype were enrolled. Images were obtained with the MP1 system (Nidek Technologies, Japan) and graded by the Doheny Image Reading Center. Best corrected VA (BCVA) was assessed using ETDRS charts. Generalized linear models with GEE were used to assess the relationships between MP1 parameters, participants’ characteristics, and BCVA while adjusting for potential within-subject correlation. Model assessment was conducted using aggregated residuals when appropriate.
Results
44 patients from 9 centers in US and Europe were enrolled. 57% were female, 91% were white, median age was 34 (11-69) years, median age of onset was 22.5 (5-63) years, and median disease duration (DD) was 9 (1-55) years. The median BCVA of N=76 study eyes was 47 letters (range 20-88;). Fixation was predominantly eccentric in 52 eyes (70%), predominantly central in 12 eyes (16%), poor central in 2 eyes (3%), and undetermined in 8 eyes (11%). Fixation was stable in 19 eyes (26%), relatively unstable in 30 eyes (41%), and unstable in 23 eyes (31%). Mean sensitivity (MS) was 11.9 (SD 5.3) dB.<br /> DD was significantly associated with the odds of fixation instability (Odds Ratio per 5 year increase in DD=1.33, p=0.05) and with MS (mean reduction of 1.2dB per 5 years DD, p<0.001). Gender and age of onset were not significantly associated with the tested MP1 parameters (p>0.05).<br /> <br /> The mean BCVA of eyes with predominantly eccentric fixation was 20 (p<0.001) letters lower compared to eyes with central fixation. Compared to eyes with stable fixation, eyes with unstable fixation had a mean reduction of 21 letters, and eyes with relative unstable fixation had a mean reduction of 13 letters. These reductions were robust after adjusting for age. Comparing patients of the same age, 1dB increase in MS was associated with an increase of 1 ETDRS letter score (p<0.001).
Conclusions
Eccentric fixation, fixation instability, and reduction in MP1 macular sensitivity were all associated with lower BCVA in patients with STGD. MP1 may offer robust parameters to assess functional damage and may be used to monitor disease progression in STGD.