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Johnny Tam, Jianfei Liu, Alfredo Dubra, Robert N Fariss; Visualization of retinal pigment epithelial cells using adaptive optics enhanced indocyanine green imaging. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4634.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the use of indocyanine green (ICG) in combination with adaptive optics (AO) in human subjects (AO-ICG) and to evaluate the uptake of ICG into retinal pigment epithelial (RPE) cells in the late phase.
An adaptive optics scanning light ophthalmoscope (AOSLO) was custom-outfitted with multimodal imaging capabilities which enabled the simultaneous collection of four different types of AOSLO images from a single 790 nm light source: confocal reflectance, split detection, dark field, and ICG fluorescence (810-840 nm detection using less than 100 µW of excitation light measured at the cornea). Multimodal AOSLO images of the inner retinal capillaries, photoreceptors, and RPE cells were acquired in six eyes of three human subjects with no history of ocular or systemic diseases. Image sequences were acquired at various time points before, during, and after the injection of ICG. In addition, histological studies in mice were carried out to confirm the specific localization of ICG to RPE cells in the late phase of ICG.
Prior to the injection of ICG dye, no detectable AO-ICG fluorescence signal could be observed. Immediately after injection, detailed images of the vasculature could be seen, confirming both entry of ICG dye into the circulation, as well as successful detection of ICG fluorescence. Two hours post injection, a non-uniform AO-ICG signal was observed in the outer retina, despite the fact that no AO-ICG signal could be detected at the time in the retinal vasculature. The recorded patterns showed good correspondence to RPE cells which were simultaneously imaged using AO dark field. Interestingly, there was a marked heterogeneity in the fluorescence of individual RPE cells. Confirmatory histological studies in mice corroborated the specific uptake of ICG by the RPE layer at a late time point after systemic ICG injection.
We demonstrate for the first time fluorescence imaging of ICG dye using the AOSLO in human subjects. The capability to simultaneously acquire four different adaptive optics modalities, namely, confocal reflectance, split detection, dark field, and ICG, significantly broadens the potential application of AOSLO for understanding disease. We also demonstrate a novel method for visualizing individual RPE cells in the living human eye, opening up new opportunities for evaluating the health and status of these cells in disease.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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