Abstract
Purpose :
Retinal diseases such as AMD have been known to lead to an acquired tritan (blue-yellow) deficit in early stages of the disease during which visual acuity is still well-preserved. However, clinical studies investigating blue-green-red sensitivity have sometimes shown conflicting results. Moreover, the role of luminance variations in color identification in early AMD has not been extensively explored. We examine color sensitivity under several luminance conditions in a population of early AMD subjects.
Methods :
A group of 27 AMD subjects (mean age 74.8 ± 6.5) were tested for color sensitivity using a computer program. Thresholds were determined for all subjects using red, green and blue Landolt C stimuli with varying saturation presented on an equiluminant background. Subjects were tested at three luminance levels in the low photopic/high mesopic range. A group of 34 normal subjects (mean age 73.9 ± 5.3) served as the control group. Fundus photographs and OCT imaging were taken and graded for all subjects. Inclusion required ETDRS BCVA of 20/40 or better for all subjects. Subjects with advanced AMD or other retinal diseases were excluded.
Results :
Mean BCVA for normal subjects was 0.03 ± 0.11 and 0.07 ± 0.12 for AMD. Mean threshold sensitivity averaged over all luminance levels for red, green and blue tests were 0.25 ± 0.018, 0.40 ± 0.024 and 0.39 ± 0.023, respectively for normal and 0.28 ± 0.020, 0.43 ± 0.030 and 0.46 ± 0.030 for AMD. Both groups showed sensitivity losses with decreased luminance level. Only mean sensitivity for blue at the highest luminance level was statistically different between groups (p=0.02).
Conclusions :
These results confirm the established vulnerability of the S-cone mediated blue visual mechanism in early AMD. Blue sensitivity may thus have potential as a clinical trial endpoint or inclusion criteria. Some loss of sensitivity appeared to be evident in the L-M cone mediated green-red visual mechanism. However, these differences were not statistically significant. Surprisingly, lower luminance conditions did not increase separation between AMD and control group means. More work needs to be done to determine the dependency of color sensitivity and low light conditions in early AMD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.