In vivo Optical Coherence Tomography of Light-Driven Melanosome Translocation in Retinal Pigment Epithelium

Abstract

Optical coherence tomography (OCT) may revolutionize fundamental investigation and clinical management of age-related macular degeneration and other eye diseases. However, quantitative OCT interpretation is hampered due to uncertain sub-cellular correlates of reflectivity in the retinal pigment epithelium (RPE) and photoreceptor. The purpose of this study was twofold: 1) to test OCT correlates in the RPE, and 2) to demonstrate the feasibility of longitudinal OCT monitoring of sub-cellular RPE dynamics. A high resolution OCT was constructed to achieve dynamic imaging of frog eyes, in which light-driven translocation of RPE melanosomes occurred within the RPE cell body and apical processes. Comparative histological examination of dark- and light-adapted eyes indicated that the RPE melanin granule, i.e., melanosome, was a primary OCT correlate. In vivo OCT imaging of RPE melanosomes opens the opportunity for quantitative assessment of RPE abnormalities associated with disease, and enables longitudinal investigation of RPE kinetics correlated with visual function.

The Effect of Retinal Melanin on Optical Coherence Tomography Images

“…Previous studies have shown that melanosomes translocate within the RPE under different light conditions in several types of fish 31–34 and frogs. 35,36 In the dark, melanosomes are transported to the basal end of RPE cells. However, in light, melanosomes are moved into the apical projections of the RPE.…”

Correlation Between Hyperreflective Foci and Clinical Outcomes in Neovascular Age-Related Macular Degeneration After Switching to Aflibercept

“…22 Three RPE grades contain epithelial and nonepithelial components (sloughed, shedding, and intraretinal). Four are epithelial only (nonuniform, very nonuniform, bilaminar, and vacuolated).…”

The Project MACULA Retinal Pigment Epithelium Grading System for Histology and Optical Coherence Tomography in Age-Related Macular Degeneration

“…The RPE is revealed in vivo by its abundant melanosomes, melanolipofuscin, and lipofuscin granules, all of lysosomal lineage, [23][24][25] and all potential subcellular contributors to SDOCT reflectivity. 26,27 Yet RPE imaging relies on surprisingly few data about the number, size, shape, and disposition of individual RPE cells and their organelles of imaging significance. Previous morphological studies of RPE in AMD and Stargardt disease, an inherited disorder also featuring abundant RPE lipofuscin, collectively used low-resolution light microscopy, electron microscopy of small series, minimally characterized or insufficiently advanced pathology, and imprecisely specified retinal localizations.…”