Purpose
To evaluate cone structure using Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) in eyes with non-neovascular age related macular degeneration (AMD), and to correlate progression of AOSLO-derived cone measures with standard measures of macular structure. High resolution imaging of cone photoreceptor morphology and quantitative measures of cone structure may enhance understanding of the pathophysiology of vision loss in AMD and provide a sensitive biomarker for disease progression.
Methods
AOSLO macular images were obtained over 12 to 21 months from 7 patients with non-neovascular AMD including 4 eyes with geographic atrophy (GA) and 6 eyes with drusen. AOSLO images were precisely superimposed onto color, infrared and autofluorescence fundus photographs and spectral domain optical coherence tomography (SD-OCT) images to allow direct correlation of cone parameters with macular structure. Cone spacing was measured for each visit in selected regions including areas over drusen (n=29), at the margin of GA (n=14), and regions without evidence of drusen or GA on fundus photos or SD-OCT (n=13) and compared to normal, age-related values.
Results
AOSLO imaging revealed intact cones up to the GA edge and overlying drusen, although subtle mosaic irregularity and reduced reflectivity often resulted in a dark signal surrounding GA margins and drusen. At baseline, cone spacing measures were normal at all study locations but 2 GA margin locations and 4 drusen locations. Although progression of GA was observed in most study eyes with standard clinical measures, AOSLO longitudinal tracking showed mild increases in cone spacing in 3 drusen locations, but stable cone spacing measures in all other drusen and GA margin locations.
Conclusions
AOSLO provides adequate resolution for quantitative measurement of cone structure at the margin of GA and over drusen in eyes with non-neovascular AMD, providing insight into the pathophysiology of GA progression. Despite reflectivity changes noted over drusen and at GA margins, cone spacing was often preserved at these locations and remained stable over time, suggesting changes in cone spacing may not represent a primary structural change in AMD progression.
Keywords: 412 age-related macular degeneration •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
688 retina