Abstract
Purpose :
Contrast sensitivity, a critical visual function task for distinguishing an object from its background, is known to be impacted in aging and in age-related macular degeneration (AMD). The goal of the current study was to compare three different contrast tests in normal and non-advanced AMD subjects.
Methods :
Twenty three subjects with non-advanced AMD (AREDS grade 1-4 on simplified scale) and thirty three age-matched normals (AREDS grade 0) were included in the study. All subjects had best VA 20/25 or better. Three different contrast tests were performed 1) Pelli-Robson CS, 2) Variable contrast flicker (VCF): computer based contrast testing using a flickering target on a mesopic background and 3) Static contrast test: computer based static stimuli of a fixed spatial frequency (0.5 and 5 cpd), under regular and low luminance condition (using 1.2 ND). Log CS assessed using Pelli-Robson letter chart was documented (higher the better). For the computer based tests (VCF and static), a staircase method was used to vary the stimulus contrast against the background and the contrast at which a subject can no longer perceive the stimulus was identified as the threshold (lower the better). The VCF contrast threshold can range from 0 to 1.
Results :
The VCF test identified significant visual dysfunction in the non-advanced AMD group (0.67±0.07) compared to normal (0.45±0.04) (p=0.005). No significant difference between the normal and the non-advanced AMD groups were identified using the Pelli-Robson contrast test (1.76±0.04 in normal vs 1.67±0.05 in AMD, p=0.14) or for any of the stimuli using the computer based static contrast test. For example, contrast threshold using the 0.5 cpd target under low luminance testing was 4.77±0.37 in normal vs 5.15±0.79 in AMD, p=0.62). There was no significant difference in ETDRS VA between the normal (0.06±0.02 logMAR) and non-advanced AMD groups (0.04±0.02 logMAR) (p=0.57).
Conclusions :
The VCF test, assessing contrast using a flickering stimuli on a mesopic background, was able to detect significant visual dysfunction in the non-advanced AMD group compared to age-matched normal controls. In the same cohort, contrast tests assessed using static targets were unable to differentiate normals vs AMDs. The VCF test could serve as a sensitive test of visual function in AMD clinical trials.
This is a 2020 ARVO Annual Meeting abstract.