In this work we report the design of a null-screen for corneal topography. To avoid the difficulties in the alignment of the test system due to the face contour (eyebrows, nose, or eyelids), we design a conical null-screen with a novel radial points distribution drawn on it in such a way that its image, which is formed by reflection on the test surface, becomes an exact array of circular spots if the surface is perfect. Additionally, an algorithm to compute the sagittal and meridional radii of curvature for the corneal surface is presented. The sagittal radius is obtained from the surface normal, and the meridional radius is calculated from a function fitted to the derivative of the sagittal curvature by using the surfacenormals raw data. Experimental results for the testing a calibration spherical surface are shown. Also, we perform some corneal topography measurements.

Date Published: 24 September 2015
PDF: 8 pages
Proc. SPIE 9628, Optical Systems Design 2015: Optical Fabrication, Testing, and Metrology V, 96281B (24 September 2015); doi: 10.1117/12.2192137

Published in SPIE Proceedings Vol. 9628:
Optical Systems Design 2015: Optical Fabrication, Testing, and Metrology V
Angela Duparré; Roland Geyl, Editor(s)