Corneal topography using a smartphone-based corneal topographer considering a biconical model for the corneal surface

Abstract

In this paper, we propose a generalization in both null-screen design and corneal surface topography retrieval algorithms to assess the nonsymmetric surface of the human cornea using a compact smartphone-based corneal topographer. The proposed new null-screen design considers the corneal surface to be a biconic surface, and the evaluation algorithms assume a general biconic shape with decentering, defocus, tilt, and rotation around the z-axis. We discussed how to integrate the measurement system to obtain geometric parameters of the corneal surface such as radius of curvature, conic constants, as well as elevation map, and sagittal and meridional curvature maps. To demonstrate that our proposed smartphone-based corneal topographer provides reliable measurements of corneal topography, we conducted measurements on a well-known biconic surface and two human corneas.