Abstract

The development of functional retinal imaging is of great interest to clinical and experimental ophthalmology because it should improve current clinical practice that relies on a simple evaluation of disease-related changes in retinal morphology. In this presentation, we will review our recent progress in the measurements and interpretation of optoretinograms (ORG). The ORG comprises light-dependent changes in photoreceptor outer segment length and scattering measured in vivo with submicrometer-resolution by Optical Coherence Tomography (OCT). Our recent data confirm that the mechanisms underlying “slow” ORG response is that extreme phototransduction increases osmotic pressure in the outer segment, driving water entry and swelling to restore osmotic balance. Water movement between different retinal layers was quantified by OCT measurements, and analysis of retinal layer thickness dynamics provided estimates of the water permeability of key barriers between the choriocapillaris (CC) and photoreceptors, viz., of the CC cell membrane, Bruch’s membrane (BrM), the RPE layer, and the rod plasma membrane. A model proposed to link the changes in refractive index caused by the osmotically driven water movement between the CC lumen and the outer segment during the ORG predicts the observed BrM scattering changes. Overall, the results and modeling provide new insights into critical water barriers of the posterior eye and an experimental and theoretical toolkit for measuring their permeabilities.

© 2023 SPIE