Adaptive optics fundus camera/Optical coherence tomography system for high resolution retinal imaging using a compact design

Abstract

Purpose : To design, build and test a compact prototype imager that is suitable for clinical environment. To combine two different imaging modalities, adaptive optics fundus camera (AO-FC) and AO-optical coherence tomography (OCT) into a single instrument.

Methods : The AO-FC is based on a commercial product (RTX1, France). The AO-OCT is operated at 840nm with an A-scan rate of 200kHz, which is translated into a volume acquisition rate of 1.25 volumes per second (2^ox2^o FOV, 400x365pixels). Both imaging modalities share the same AO correction path. The relay optics of the AO system is entirely based on lenses, which allows a very compact design. AO runs in closed loop mode and is based on wavefront measurements using a Hartmann Shack wavefront sensor in combination with a laser beacon. Wavefront correction is done using a 52 element deformable mirror (Mirao 52e). The sample arm including the fundus camera, wavefront sensing and wavefront correcting part has an extension of 40cmx50cmx20cm and is mounted on a 3D translation stage which is operable by a joystick.

Results : The instrument has been tested in healthy volunteers, in patients with Stargardt disease (SD) and diabetic retinopathy (DR). In SD abnormal cone spacing and cone morphology was observed on the AO-FC images. In the AO-OCT data sets hyper-reflective flecks of lipofuscin were clearly resolved in depth. In DR the focus was set on the visualization of microaneurysms. AO-OCT allows a clear 3D observation and an accurate localization of these structures. The content of microaneurysms can be visualized without disturbing lensing effect. Finally, AO-OCT allows measuring the volumes of these microaneurysms which might be of importance for follow up studies.

Conclusions : The AO-fundus camera provides a fast preview with larger field of view which simplifies subject alignment and localization of the regions of interest. Complementary information is provided and a comparison with other state of the art imaging modalities is simplified. The instrument is easy to use and can be operated with a single person which fits well for a more widespread clinical use of the instrument.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

A) AO-fundus image (4^ox4^o) recorded from a healthy volunteer, B) Single B-scan acquired at the location indicated with a green line, C) Average of 30 B-scans from the volume scan, D) Extracted en-face image from the AO-OCT volume.