Non-mydriatic chorioretinal imaging in a transmission geometry and application to retinal oximetry

The human retina is typically imaged in a reflection geometry, where light is delivered through the pupil and images are formed from the light reflected back from the retina. In this configuration, artifacts caused by retinal surface reflex are often encountered, which complicate quantitative interpretation of the reflection images. We present an alternative illumination method, which avoids these artifacts. The method uses deeply penetrating near-infrared (NIR) light delivered transcranially from the side of the head, and exploits multiple scattering to redirect a portion of the light towards the posterior eye. This unique transmission geometry simplifies absorption measurements and enables flash-free, non-mydriatic imaging as deep as the choroid. Images taken with this new transillumination approach are applied to retinal oximetry.