Spectrally Resolved Fundus Autofluorescence in ABCA4-Related Retinopathy

To investigate the green and red fluorescence emission component of hyperautofluorescent flecks in patients with ABCA4-related retinopathy.

A confocal light-emitting diode (LED)-based retinal imaging system (EIDON) was used for image acquisition of patients with genetically confirmed ABCA4 mutations. Using 450-nm excitation wavelengths, spectrally resolved retinal autofluorescence images were acquired in two wavelength ranges: green emission fluorescent component (GEFC, 500-560 nm), and red emission fluorescent component (REFC, 560-700 nm). Image analysis included comparison of the two emission spectra, correlation with confocal EIDON LED color fundus images, and spectral-domain optical coherence tomography (OCT).

Eighty eyes of 40 patients with ABCA4-related retinopathy were examined. A characteristic distribution of flecks with distinct pattern of fluorescence emission components was detected and quantified. Independent from disease manifestation, different proportions of GEFC and REFC were identified within single flecks. Centrally located flecks showed a higher proportion of GEFC and were characterized by local disruption of outer retinal bands in OCT. More peripheral flecks were more prominent in the REFC and correlated to subretinal hyperreflective deposits with only minor pathologic alterations of outer retinal layers. Individual flecks even showed spatial differences of the predominant fluorescent component.

Spectrally resolved fundus autofluorescence intensity images feature characteristic distribution of GEFC and REFC in flecks, highlighting the heterogeneity of fluorophore distribution and providing more insight into the pathogenesis of ABCA4-related retinopathy. In view of upcoming therapeutic trials, longitudinal analysis of fluorescent components might facilitate monitoring of subtle disease progression and/or treatment effects.