Multimodal imaging of the retinal neurons and underlying epithelial cells in the living human eye using adaptive optics enhanced infrared autofluorescence

Authors

• T Liu
• H Jung
• J Liu
• M Droettboom
• J Tam

Abstract

Retinal pigment epithelial (RPE) cells play a fundamental role in supporting and maintaining the light sensitive neurons of the eye (photoreceptors), but imaging RPE cells in the living human eye has been challenging due to the absorption of light by melanin pigment. We demonstrate a new method to simultaneously visualize both RPE cells and overlying photoreceptors, using a custom-built Adaptive Optics (AO) instrument with a novel Infrared Autofluorescence (IRAF) imaging channel, which takes advantage of the autofluorescence signal presumably arising from the melanin inside RPE cells. Overlapping videos were collected in 13 healthy subjects at different retinal locations ranging from the fovea out to 6mm eccentricity, and then averaged and assembled into a montage. Compared to conventional IRAF, AO-IRAF images showed a considerable improvement in resolution, enabling in vivo quantitative analysis of the RPE mosaic. RPE cell density ranged from 6505 to 5388 cells/mm2 for the areas measured. We also identified cone photoreceptors on simultaneously-acquired AO images that were co-registered to the AO-IRAF images of RPE cells and found that RPE cells support on average up to 20.15 cone photoreceptors in the fovea down to an average of 1.03 cone photoreceptors at 6.0 mm eccentricity. These results were in general agreement with previous studies. We present a novel AO modality that can reveal the cellular details of the RPE mosaic, which can be juxtaposed with AO images of light sensitive neurons, establishing a potential path for investigating the changes of the photoreceptor-RPE complex in patients with blinding retinal diseases.

Scientific Focus Area: Biomedical Engineering and Biophysics

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