Swept Source Enhanced Depth Imaging Optical Coherence Tomography

Overview

The investigators would be interested in applying the enhanced depth imaging technique to swept source optical coherence tomography, by modifying the acquisition protocol. Doing so, the investigators hope to improve the visualization of the choroid and perhaps even of the sclera.

A structurally and functionally normal choroidal vasculature is essential for retinal function. The status of the choroid appears to be a crucial determinant in the pathogenesis of diseases such as age-related choroidal atrophy, myopic chorioretinal atrophy, central serous chorioretinopathy, chorioretinal inflammatory diseases, and tumors. The in vivo structure of the choroid in health and disease is incompletely visualized with traditional imaging modalities, including indocyanine green angiography and ultrasonography. Optical coherence tomography (OCT) is an established medical imaging technique that uses light to capture micrometer-resolution, three-dimensional images from within optical scattering media. OCT is based on low-coherence interferometry. Nowadays, it is essential for managing retinal conditions. Unfortunately, standard spectral domain optic coherence tomography (SD-OCT) is of limited use in imaging choroidal morphology. A modification to the standard technique, termed enhanced depth imaging optical coherence tomography (EDI-OCT), is able to image the choroid with better clarity using commercial SD-OCTs. With the advent of enhanced depth imaging optical coherence tomography (EDI-OCT), detailed visualisation of the choroid in vivo has been made possible possible. Measurements of choroidal thickness (CT) have also enabled new directions in research to study normal and pathological processes within the choroid. However, EDI-OCT has its own limitations: the outer choroidal border cannot always be visualized and choroidal details sometime lack clarity. A new generation of OCTs has been made available, based on swept-source technology. Swept source OCT (SS-OCT) has been shown to be more precise than spectral domain EDI-OCT in measuring choroidal thickness. Our department is now using two OCTs, one is a SD- OCT (Canon HS-100), the other one a SS- OCT (Topcon DRI Atlantis). The investigators would be interested in applying the EDI technique to SS- OCT, by modifying the acquisition protocol. Doing so, the investigators hope to improve the visualization of the choroid and perhaps even of the sclera. This modification is based on the technique described by Spaide for SD-OCT. From the patient's perspective, it only involves spending more time fixing the green stimulus (about 4 minutes instead of 2, in order to follow the swept-source EDI protocol in addition to standard swept source).

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