3D visualization and mapping of choroid thickness based on optical coherence tomography: A step-by-step geometric approach

Although bodily organs are inherently 3D, medical diagnosis often relies on their 2D representation. For instance, sectional images of the eye (especially, of its posterior part) based on optical coherence tomography (OCT) provide internal views, from which the ophthalmologist makes medical decisions about 3D eye structures. In the course, the physician is forced to mentally synthesize the underlying 3D context, which could be both time consuming and stressful. In this backdrop, can such 2D sections be arranged and presented in the natural 3D form for faster and stress-free diagnosis? In this paper, we consider ailments affecting choroid thickness, and address the aforementioned question at two levels-in terms of 3D visualization and 3D mapping. In particular, we exploit the spherical geometry of the eye, align OCT sections on a nominal sphere, and extract the choroid by peeling off inner and outer layers. At each step, we render our intermediate results on a 3D lightfield display, which provides a natural visual representation. Finally, the thickness variation of the extracted choroid is spatially mapped, and observed on a lightfield display as well as using 3D visualization softwares on a regular 2D terminal. Consequently, we identified choroid depletion around optic disc based on the test OCT images. We believe that the proposed technique would provide ophthalmologists with a tool for making faster diagnostic decisions with less stress.