Abstract
Purpose :
Decreased low luminance visual acuity as a measure of cone dysfunction and reduced scotopic sensitivity as an indicator of rod dysfunction are both observed in patients with AMD. Diffuse retina pigment epithelial dysfunction leading to both rod and cone dysfunction has been hypothesized as a major pathologic mechanism in AMD. The goal of the present study was to test this hypothesis by examining the relationship between LLD and sMPS in patients with AMD.
Methods :
Subjects with early AMD (n=6, age 63.7 ±4.7), intermediate (n=31, age 73.6 ±9.9), geographic atrophy (GA) (n=8, age 74.7 ±7.0), and age-matched controls (n=8, age 67.8 ±9.3) were examined. Following 30 minutes of dark adaptation, sMPS’s were measured at 56 locations with a spot size 3 within 10° of the fovea, aligned to OCT using a modified fundus microperimeter (MP-1S, Nidek Technologies) and neutral density filters to adjust the dynamic range. Points falling on patches of GA were eliminated. ETDRS visual acuity was measured. Low luminance visual acuity was measured by introducing an occluder with a 2.0 ND filter. LLD were calculated by subtracting the low luminance values from the normal luminance. Relationships were evaluated using Pearson’s correlation coefficient (r).
Results :
In the control group the average LLD was 11.5 ±3.03 letters, and the average sMPS was 19.73 ±5.08 dB. For the early AMD group LLD was 16.4 ±10.4 letters, and sMPS was 19.40 ±7.31 dB. In the intermediate group LLD was 15.2 ±6.24 letters, and the sMPS was 19.31 ±3.83 dB. In the GA group the LLD was 18.0 ±9.18 letters, and the sMPS was 16.4 ±4.93 dB. There was no significant correlation between LLD and sMPS overall (r=0.124, p=0.929), in the early group (r=0.191, p=0.716), nor in the intermediate group (r=-0.010, p=0.956). However, there was a negative correlation in the normal group (r=-0.740, p=0.0360) but a positive correlation in the GA group (r=0.696, p=0.0372).
Conclusions :
Aging appears to affect global photoreceptor function as demonstrated by a correlation between a larger LLD and a decrease in sMPS. However increasing severity of AMD appears to selectively affect either the rods or cones but not both, while in patients with GA there appears to be a large effect on rods selectively rather than cones. These data do not support the hypothesis of generalized diffuse photoreceptor dysfunction in AMD.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.