In Vivo Microscopic Imaging of Drusen using Adaptive Optics

Abstract

Purpose: : To characterize the aspect of age-related and familial drusen at the microscopic scale as well as the structure of the overlying and neighbouring cone photoreceptors.

Methods: : 4 patients with age-related drusen and 2 cases of familial drusen underwent high resolution spectral domain optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) examinations (Spectralis HRA+OCT, Heidelberg, Germany). The same eyes were analyzed using an adaptive optics retinal camera (rtx1, Imagine Eyes, Orsay, France) at eccentricities ranging from 0 deg to 4 deg from the foveola. The resulting AO images were registered with the corresponding OCT and SLO images.

Results: : In AO images, most drusen appeared as doughnut-shaped highly reflective zones. AO provided detailed images of very small familial drusen that were barely detectable using SLO and OCT. The overlying cone mosaic was also observed in all AO images, yet it exhibited local losses in cell visibility in several areas. The comparison with matched OCT data showed that areas with reduced cone visibility were located over the drusen slopes. Cones were almost always visible at the top of drusen. In the flat retinal areas that surrounded drusen, the cones were organized in a normal mosaic pattern.

Conclusions: : The AO retinal camera provided enhanced sensitivity in detecting and mapping drusen. The regularity of the cone mosaic observed over the top of drusen and between drusen suggested that the presence of drusen might have limited impact on photoreceptor metabolism. Local losses in cone contrast at the drusen slopes confirm a strong relation between cone visibility and their orientation. These results lead us to anticipate that the AO retinal camera will be a powerful tool for quantifying spontaneous or therapeutic changes in drusen quantity and morphology.

Keywords: photoreceptors • retina • imaging/image analysis: non-clinical