Autofluorescence Imaging for Diagnosis and Follow-up of Cystoid Macular Edema

Lipofuscin results from digestion of photoreceptor outer segments by the retinal pigment epithelium (RPE) and is the principal compound that causes RPE fluorescence during autofluorescence imaging. Absorption of the 488-nanometer blue light by macular pigments, especially by the carotenoids lutein and zeaxanthin, causes normal macular hypo-autofluorescence. Fundus autofluorescence imaging is being increasingly employed in ophthalmic practice to diagnose and monitor patients with a variety of retinal disorders. In macular edema for example, areas of hyper-autofluorescence are usually present which are postulated to be due to dispersion of macular pigments by pockets of intraretinal fluid. For this reason, the masking effect of macular pigments is reduced and the natural autofluorescence of lipofuscin can be observed without interference. In cystic types of macular edema, e.g. cystoid macular edema due to retinal vein occlusion, diabetic macular edema and post cataract surgery, hyperautofluorescent regions corresponding to cystic spaces of fluid accumulation can be identified. In addition, the amount of hyper-autofluorescence seems to correspond to the severity of edema. Hence, autofluorescence imaging, as a noninvasive technique, can provide valuable information on cystoid macular edema in terms of diagnosis, followup and efficacy of treatment.