Confocal scanner gives ophthalmologists valuable new tool
Most ocular structures become luminescent for a short time when exposed to a light source of appropriate wavelength; this phenomenon is known as autofluorescence (AF). AF is due to the presence of fluorescent substances called fluorophores. Of special importance for diagnostic purposes is the autofluorescence of the ocular fundus (fundus autofluorescence; FAF) caused by the presence of lipofuscin, the most important fluorophore of the retinal pigment epithelium (RPE).
Lipofuscin is the product of degradation of the outer segment disks of photoreceptors, which in normal conditions are phagocytised by RPE cells. Many retinal pathologies cause accumulation or depletion of lipofuscin, and consequently, an increase or a reduction of autofluorescence. FAF is increased in the following diseases: age-related macular degeneration; Stargardt disease; Best disease; and adult-onset foveomacular vitelliform macular dystrophy. Levels are also raised in the drusen of the sub-pigment epithelial space and in choroidal tumours, such as nevi and melanomas.
Reduced or absent FAF occurs in cases of damage of the RPE, as in geographic atrophy, cystoid macular oedema, and in recent retinal haemorrhages. Sometimes, the alterations of FAF precede the anatomic alterations, hence FAF imaging is being considered as increasingly important for the evaluation of patients with fundus alterations.