Abstract
Purpose: :
To construct and validate autofluorescence (AF) metrics in Stargardt disease (STGD).
Methods: :
We studied the AF scans OU of 10 patients with STGD. Four had serial scans. Some methods were extensions of techniques we had previously validated for analysis of age-related macular degeneration, including measurement of area and geometry of geographic atrophy (GA) (Huang et al, IOVS, 2006), finding the area and distribution of focally increased autofluorescence (FIAF) by leveling the AF scan background with a mathematical model (Smith et al, IOVS, 2006), and registering the final image into point-wise correspondence with the initial image for analysis of GA and FIAF changes in serial images. New techniques for STGD included level sets to measure the boundaries of rings of increased AF, their contour levels, and their progression. We defined FIAF dispersion as the weighted average radius of FIAF fleck pixels (similarly for hypoautofluorescence (hypoAF) dispersion) and used these metrics to track centrifugal patterns of flecks with FIAF and hypoAF.
Results: :
GA central lesions tended to grow uniformly centrifugally, with no quadrantic preference. Active hyperautofluorescent rings tended to increase in size, spread temporally and maintain their nasal boundaries. More peripheral, newer flecks tended to be hyperautofluorescent and the more central, older flecks hypoautofluorescent, so that FIAF dispersion and hypoAF dispersion were both increasing in time, with FIAF dispersion always greater than hypoAF dispersion.
Conclusions: :
Because AF identifies lipofuscin accumulation and GA so specifically, and because these are the most characteristic biologic markers of STGD, autofluorescence metrics in STGD merit consideration as quantitative disease markers.
Keywords: imaging/image analysis: clinical • retinal degenerations: hereditary • ipofuscin