Near-infrared autofluorescence imaging of the fundus: Visualization of ocular melanin

PURPOSE. To evaluate the origin of the near-infrared autofluorescence ( AF) of the fundus detected by scanning laser ophthalmoscopy and compare the distribution of this AF with that of lipofuscin. METHODS. AF [ 787] fundus images ( excitation [ Exc.] 787 nm; emission [ Emi.] > 800 nm) were recorded with a confocal scanning laser ophthalmoscope, in 85 normal subjects ( ages: 11 - 77 years) and in 25 patients with AMD and other retinal diseases. Standard AF [ 488] images ( Exc. 488 nm; Emi. > 500 nm) were recorded in a subset of the population. RESULTS. The fovea exhibits higher AF[ 787] than the perifovea in an area > 8 degrees in diameter, roughly equivalent to the area of higher RPE melanin seen in AF[ 488] and color images. The ratio of foveal to perifoveal AF[ 787] decreases with age ( P < 0.0001) and is higher in subjects with light irides ( P = 0.04). Higher AF[ 787] emanates from hyperpigmentation, from the choroidal pigment ( nevi, outer layers) and from the pigment epithelium and stroma of the iris. Low AF[ 787] is observed in geographic atrophy particularly in subjects with light irides. CONCLUSIONS. AF[ 787] originates from the RPE and to a varying degree from the choroid. Oxidized melanin, or compounds closely associated with melanin, contributes substantially to this AF, but other fluorophores cannot be excluded at this stage. Confocal AF[ 787] imaging may provide a new modality to visualize pathologic features of the RPE and the choroid, and, together with AF[ 488] imaging, offers a new tool to study biological changes associated with aging of the RPE and pathology.