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 AF787 than the perifovea in an area approximately 8 degrees in diameter, roughly equivalent to the area of higher RPE melanin seen in AF488 and color images. The ratio of foveal to perifoveal AF787 decreases with age (P < 0.0001) and is higher in subjects with light irides (P = 0.04). Higher AF787 emanates from hyperpigmentation, from the choroidal pigment (nevi, outer layers) and from the pigment epithelium and stroma of the iris. Low AF787 is observed in geographic atrophy particularly in subjects with light irides. CONCLUSIONS: AF787 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 AF787 imaging may provide a new modality to visualize pathologic features of the RPE and the choroid, and, together with AF488 imaging, offers a new tool to study biological changes associated with aging of the RPE and pathology.