Review of fundus autofluorescence in choroidal melanocytic lesions

Fundus autofluorescence (FAF) imaging takes advantage of the fluorescent properties of some molecules, especially lipofuscin. FAF derives mainly from retinal pigment epithelium (RPE) and Bruch's membrane. Using confocal scanning laser ophthalmoscope (cSLO) we have previously shown that FAF associated with pigmented choroidal lesions can be attributed to mainly lipofuscin (orange pigment) within the RPE. Other causes of FAF include hyperpigmentation, drusen, or fibrous metaplasia probably because they also cause lipofuscin accumulation in the overlying RPE. There is a total or partial correlation between FAF and the foci of lipofuscin and hyperpigmentation in about 90% of the cases. The FAF patterns of choroidal melanocytic lesions were classified as patchy or diffuse. The patchy pattern was defined as the presence of distinct areas of increased FAF between areas of normal autofluorescence. The diffuse pattern was characterized by the presence of increased FAF with indistinct borders over a larger part (>50%) of the tumour in the absence of such intervening areas. Choroidal melanomas presented with either a diffuse or patchy pattern, whereas choroidal naevi demonstrated only the patchy pattern. Diffuse FAF pattern was more often associated with larger choroidal melanomas as well as with early venous and late hyperfluorescence on fluorescein angiography. Limitations of these observations depend on the field of depth of cSLO; thus, FAF from other planes could not be detected. Increased retinal thickness, intraretinal oedema, or presence of subretinal fluid may also affect the FAF signal.