Abstract
Purpose :
Light that ultimately forms fundus photographs is a summation of multiple reflections from several stratified fundus tissue layers. Reflections from the inner retina dominate and obscure the visibility of deeper structure, such as the retinal pigment epithelium (RPE) and choroid. We propose an alternative imaging strategy based on transmitted light, which avoids such unwanted superficial reflections.
Methods :
The imaging technique is based on light delivered transcranially through the subject’s temple. Near-infrared (NIR) light from a high-power LED source is coupled into a fiber bundle, the distal end of which is placed on the subject’s temple. NIR light penetrates deeply in tissue due to its low absorption and scattering, and thus sufficient light is available at the back of the eye to enable transmission imaging with a standard fundus camera equipped with a NIR-sensitive image sensor.
Results :
An example of fundus transillumination is shown in the attached figure. An image taken using a 940 nm LED and a non-mydriatic fundus camera reveals major retinal vessels and aspects of the deeper choroidal vortex veins. As predicted, the images are free from superficial back-reflections.
Conclusions :
Near infrared light penetrates deeply through the skull and thus enables transmission widefield fundus imaging. Our strategy is compatible with existing fundus cameras, enabling transmission and reflection modalities to be operated quasi-simultaneously, allowing a direct comparison of the two modalities and a potential fusion of the information they provide.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.