Abstract
Purpose :
The study examines the effects of polarization control on fundus imaging, and demonstrates the feasibility of selecting polarization maintaining photons for enhanced contrast imaging of the retina.
Methods :
Orthogonal polarization control is frequently used in conventional fundus imagers (Fig. 1A) to minimize reflection artifacts from the ophthalmic lens (OL). However, this may also reject the directly reflected photons from the superficial layer of the retina, which preserve the polarization condition of incident light, thus reduce the contrast of retinal image. In our proposed system (Fig. 1B), the horizontally polarized light from the light source (LS) passes the quarter waveplate (QW) and becomes circularly polarized light before entering the retina. This configuration provides an orthogonal polarization control to reject reflected light from the OL and a parallel polarization configuration for fundus imaging.
Results :
Representative images captured using the imaging settings in Figures 1A and 1B are shown in Figures 2A and 2B, respectively. Evidently the retinal image contrast increases both in the color images and RGB channel images with the parallel polarization control. The ratio of average intensity of red and green channel in the images taken with orthogonal polarization control for fundus imaging is (1.267±0.0934): 1, whereas it becomes (1.047±0.0464): 1 with the parallel polarization control. As green light is mostly reflected by the superficial retina, more photons preserve their original polarization property compared to red light with higher penetration capability. Therefore, preservation of the polarization maintaining photons increases the relative intensity of the green channel.
Conclusions :
We have demonstrated a fundus imaging system with orthogonal polarization control to reject back-reflected light from the ophthalmic lens and parallel polarization control for enhanced contrast retinal imaging.
This abstract was presented at the 2023 ARVO Imaging in the Eye Conference, held in New Orleans, LA, April 21-22, 2023.