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A. E. Elsner, D. A. VanNasdale, Jr., B. P. Haggerty, R. C. Gustus, B. L. Petrig; Mapping Fundus Autofluorescence in the Central Macula. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5167.
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To detect the earliest changes possible in the retinal pigment epithelium due to aging or the initial stages of age-related macular degeneration. To map fundus autofluorescence in the central macula of humans that provides fine spatial detail and is not masked by absorption from macular pigment, choroidal melanin, or photopigment.
We used a research scanning laser ophthalmoscope to illuminate the fundus of normal subjects, aged 31, 50, 58, and 58 yr. To image readily through macular pigment, we used 594 nm illumination at 0.60 microwatts/cm2, which we previously showed was bright enough to bleach foveal cone photopigments and remove their transmission artifacts. Visual field size was varied, but the most successful results were obtained from the 29 x 23 deg field of view, which provided a view of the optic disc and major retinal vessels for landmarks to align multiple images. Autofluorescence images were acquired using a barrier filter that cut on at about 600 nm, with > 5 log units of extinction at the illumination wavelength, virtually eliminating pseudo-fluorescence. We collected both reflectance and fluorescence data, in separate series of 92 images each, which required about 3 sec, and varied the gain of the detector and capture card across series. We documented fundus status by polarimetric imaging (GDx, Zeiss) and en face near infrared imaging with spectral domain OCT (Spectralis, Heidelberg Engineering).
The average of 30 or more aufofluorescences images led to maps of autofluorescence that revealed foveal detail. Individual autofluorescence images were dim and noisy, and extremely dim in the youngest subject. The retinal vessels and optic nerve were visible as uniformly darker than the surrounding fundus, as expected. Vessels in the central macula were detectable down to the 4th and sometimes 5th branch. In one older subject, a region of early changes to the retinal pigment epithelium, seen as uneven autofluorescence, was supported by data from both the OCT and GDx at that location. Another older subject lacked these changes in the near infrared, en face imaging, and the autofluorescence data agreed.
A strikingly better autofluorescence map of the central macular region of subjects with macular pigment is produced with 594 nm illumination, compared to the more typical 488 nm. Laser scanning and image averaging produce relatively sharp images that can reveal small and subtle features over the entire macular region.
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