Miniaturized indirect illumination with light polarization and power controls for high dynamic range fundus photography

Fundus imaging is indispensable for clinical management of eye diseases such as diabetic retinopathy (DR), age-related macular degeneration (AMD), and glaucoma. Emerging portable and smartphone fundus cameras hold promise to advance telemedicine ophthalmology in home and family care environments. However, currently available portable fundus cameras have limited field of view (FOV). Miniaturized indirect ophthalmoscopy illumination has been recently demonstrated as a feasible solution to expand the FOV in portable fundus cameras. However, for the indirect illumination, the light reflected from the ophthalmic lens causes image artifacts. Moreover, the image contrast of a local fundus region can be limited as the light efficiency varies significantly among different regions, such as the optic nerve head and central fovea. We report here a portable, non-mydriatic, reflectance artifact free, high dynamic range (HDR) fundus camera with a 67° visual-angle (101° eye-angle) snapshot FOV. Orthogonal polarization control was used to eliminate illumination reflectance artifact due to the ophthalmic lens back-reflection. With independent power control, three sequential fundus images were captured within the pupillary reflex time. These three images, with different local features enhanced, are registered, and fused together to get the HDR image. The output HDR images shows better biomarker contrast compared to input low dynamic range (LDR) images.