Low Luminance Visual Acuity and Treatment Response in Patients with wet Age-Related Macular Degeneration Enrolled in the HARBOR Study

Abstract

 

Purpose

 

Explore the effect of baseline low luminance visual acuity (LLVA) score on best corrected visual acuity (BCVA) response to ranibizumab treatment in patients with subfoveal wet AMD (n = 1097).

 

Methods

 

Subanalysis of the HARBOR study (NCT00891735). LLVA was measured by placing a 2.0-log-unit neutral density filter and having the participant read the normally illuminated ETDRS chart. The relationship of LLVA with BCVA at baseline and over 24 months of treatment (months 3, 6, 9, 12, 15, 18, 21, and 24) was explored using Pearson correlation.

 

Results

 

Mean baseline LLVA was similar across treatment groups (28.2 to 29.3 letters) and was significantly correlated with baseline BCVA (P<.0001). On average for all treatment groups pooled, LLVA increased by 15.4 letters from baseline to month 24, compared with 8.7 letters gain in BCVA. Therefore, the effect of treatment under low luminance conditions was underestimated by BCVA measurements, but it is likely meaningful to patients. The magnitude of the difference (gap) between BCVA and LLVA at baseline (but not the absolute baseline value of LLVA) was negatively correlated with BCVA gain at month 24 (P<.0001). Patients with ≤17 letters difference between BCVA and LLVA at baseline gained on average 13.4 letters BCVA at month 24 while patients with ≥33 letters difference gained only 2.4 letters BCVA (Figure).

 

Conclusions

 

LLVA was correlated with BCVA and showed a robust response to treatment. While baseline LLVA itself was not associated with a differential treatment effect, patients with a wider gap between the BCVA and LLVA scores at baseline gained less BCVA during the 24 month treatment period than those whose baseline LLVA and BCVA were more similar. Therefore a small BCVA-LLVA differential may be a manifestation of a milder retinal impairment and a predictor of greater capacity for visual function improvement with ranibizumab therapy.

 

 

BCVA mean change from baseline (EDTRS letters) by BCVA/LLVA gap quartile (letters). All treatment groups pooled. Error bars represent 95% confidence interval of the mean.

 

Keywords: 412 age-related macular degeneration • 754 visual acuity • 466 clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials