Purpose:
The use of a functional test in early AMD may provide a marker of disease severity which could be followed over time to chart progression. However the relationship between clinical fundus changes and retinal function in AMD has not been well investigated. In this study, we examined the relationship between AMD severity based on fundus appearance and visual function assessed by static and flicker perimetry.
Methods:
This cross sectional study involved 279 AMD participants (71.6 ± 10.4 years) with various clinical grades of AMD severity and 24 normal participants without AMD (61.0 ± 12.4 years). The clinical status of the study eye was graded according to the fundus appearance in both eyes. AMD severity was subdivided into 10 groups ranging from hard drusen to non-foveal geographic atrophy. All participants underwent static and flicker perimetry testing in the same session. Both test consisted of 48 test points located at 1, 3, 6 and 10 degrees. The static and flicker thresholds of various AMD grades were compared.
Results:
The pattern of change in static thresholds across the AMD grades was very similar to that of the flicker threshold changes although the absolute thresholds were consistently higher in the flicker groups across all classifications of AMD. Both static and flicker thresholds were proportionally increased as AMD severity increased. Significant increases in static and flicker thresholds within the central 3 degrees were detected in 6/10 AMD groups including groups with soft drusen (p<0.001) and non-foveal geographic atrophy (p<0.001). Neither static nor flicker threshold was significantly elevated in eyes with hard (p=1.000) or intermediate (p=1.000) drusen compared to normal eyes.
Conclusions:
AMD severity graded by fundus appearance correlates well with the degree of visual dysfunction as measured by static and flicker perimetry. Both static and flicker perimetry appear to be equally affected at all levels of AMD severity. Increases in clinical severity grade were associated with a greater reduction in visual function. Perimetry may prove a useful outcome measure to assess progression of early AMD.
Keywords: age-related macular degeneration • perimetry