Purpose:
A biomarker of early age-related macular degeneration (AMD) which could be used to follow change over time, predict progression to geographic atrophy (GA) and determine treatment efficacy is urgently required. Using flicker perimetry, our aim was to determine the pattern of flicker sensitivity changes prior to clinically detectable GA.
Methods:
In this prospective study, we recruited 182 subjects with early AMD and 24 age-matched normal controls, and followed them at 6 monthly intervals. At each visit, all subjects underwent a clinical eye examination, retinal imaging and flicker visual field testing. The changes in flicker sensitivity of 24 tested locations within the central 6 degrees over 3 visits prior to the development of atrophy were examined.
Results:
Of the 182 participants, GA developed in 16 eyes of 16 subjects during the study period. The mean follow up duration was 4.0 years and ranged from 1.5 to 5.0 years. Having taken the rate of change of each test location, the average rate of change in flicker sensitivity over the last 3 consecutive visits in eyes without AMD was -0.003 dB/month (95% CI: -0.021 - 0.015). In eyes that went on to develop GA, there was a greater linear reduction in flicker sensitivity over time of 0.38±0.41 dB/month (p=0.017) in the areas that went on to develop GA. A wide-spread reduction in flicker sensitivity was also observed in non-atrophic areas but the rate of change in sensitivity was less (-0.07±0.37 dB/month, p=0.008).
Conclusions:
The flicker sensitivity within the central 6 degrees was significantly reduced not only at the time GA was detected but also prior to clinically detectable GA. Retinal locations with a greater rate of change in flicker sensitivity appear to correlate with areas that went on to develop atrophy. These findings suggest that flicker perimetry parameters could have a potential role in predicting GA development, monitoring disease progression and determining the efficacy of treatments aimed at slowing progression of disease.
Keywords: age-related macular degeneration • perimetry • visual fields