Autofluorescence of the cells in human subretinal fluid

The origin of autofluorescence in the subretinal space and the autofluorescence properties of the cells were investigated in surgically collected subretinal fluid.

Subretinal fluid was surgically collected from four eyes of patients with rhegmatogenous retinal detachment (three eyes) and Coats' disease (one eye). After cytocentrifuge preparation of the cells in the fluid and immunofluorescence staining, a cytologic examination was conducted by using confocal scanning laser microscopy. The autofluorescence of the cells was elucidated by measuring the fluorescence spectra with spectroscopy, to obtain different excitation laser light emission fingerprints.

The cells from the subretinal fluid were classified into three types: CD68-negative cells containing numerous pigmented granules, CD68-positive cells containing few pigments, and CD68-negative cells with no pigmented granules. Autofluorescence was observed in the inclusions of the cells classified into the former two types. When the cells were excited by a 458- or 488-nm laser light, emission spectra in autofluorescence showed little difference between CD68-positive and -negative cells. Peak analysis confirmed that the two types of cells showed the same emission peaks within this range of excitation light.

Autofluorescent inclusions appeared in the CD68-positive and -negative cells in the subretinal fluid. The macrophages in the subretinal fluid possess autofluorescence that is spectroscopically similar to lipofuscin. Autofluorescence of macrophages can be attributed to degenerated outer segments and debris from apoptotic photoreceptors. Clinicians should consider migration of macrophages, in addition to retinal pigment epithelium, as the possible source when abnormal fundus autofluorescence is observed using an ordinary set of fluorescence filters.