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Hae Won Jung, Jianfei Liu, Alfredo Dubra, Johnny Tam; In vivo imaging of the choriocapillaris using adaptive optics enhanced indocyanine green ophthalmoscopy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):296.
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© ARVO (1962-2015); The Authors (2016-present)
In vivo imaging of the choriocapillaris has been difficult due to its thinness and location behind the retinal pigment epithelial (RPE) cells, which contain light-absorbing melanin granules. Indocyanine green (ICG) can be used to visualize the choroidal vasculature, but conventional ICG imaging is unable to reliably visualize the mesh-like structure of the choriocapillaris. We explore the feasibility of using adaptive optics enhanced indocyanine green ophthalmoscopy (AO-ICG) to image the choriocapillaris in the living human eye (IOVS 2016;57:4376-4384).
A custom-built adaptive optics scanning light ophthalmoscope (AOSLO) was used to image eyes from 5 subjects with no history of ocular or systemic diseases (age range 22-47 years; ex/em 790/810-840nm; imaging light power measured at cornea 125 µW; detection pinhole size 3-6 Airy units). AO-ICG videos were acquired at the fovea during intravenous injection of ICG, and then post-processed to remove eye motion. Stabilized AO-ICG videos were further averaged at various intervals within the dye transit to extract the choriocapillaris signal. Images were compared to three previously-published histological images to quantitatively assess sizes of observed pores.
In all subjects and in agreement with our previous findings, there was a rapid uptake of ICG into punctate spots which hindered the visualization of the choriocapillaris. These spots colocalized with outlines of RPE cells which could be visualized from simultaneously-captured and co-registered darkfield images. Thus, videos were separated into two portions corresponding to the rise in signal from the transit of the initial injection bolus and a residual signal approximately 0.5-1 minutes later. This resulted in two images of the combined choriocapillaris and RPE signals in which the first portion contained a stronger choriocapillaris signal when compared to the second. Subtraction of these two images revealed a mesh-like structure that resembled the choriocapillaris. The area of imaged pores at the fovea, 307±73 µm2 (n=199), was not significantly different compared to those measured from histology, 249±122 µm2 (n=133) (mean±SD, p=0.42).
AO-ICG can be used to visualize perfusion of the choriocapillaris in the living human eye which may lead to new insights about the onset and progression of diseases such as age related macular degeneration.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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