Imaging and qualitative depth analysis with a portable nonmydriatic fundus camera using oblique illumination

Abstract

The photographic assessment of the optic nerve has been one of the original and most extensively used methods to evaluate patients for glaucoma. The depth evaluation of the optic disc in the retinal fundus is important for the early detection of glaucoma. Conventional fundus cameras have a limited field-of-view for imaging of the retina and its peripheral areas. In this article, we report the design and fabrication of a non-mydriatic wide-field fundus camera using a contact-free trans-scleral illumination that is capable of taking 3D images of the optic disc using oblique illumination. We demonstrate that, using oblique illumination through sclera, a quasi 3D image of the optic disc along with its shadow can be obtained. The shadow provides important information on the shape and depth of the optic disc. The depth values of the optic disc obtained by our proposed method using shadow length measurements are in good agreement with the values obtained using an optical coherence tomography device. The results indicate that our fabricated fundus camera could be an easy-to-handle and low-cost tool for remote detection and diagnosis of ocular diseases without the need of an ophthalmologist.