To assess the curvature of a fast free-form convex surface, such as the cornea of the human eye, a smartphone corneal topographer based on the null-screen method has been developed. The null screen consists of a semiradial distribution of ellipse-shape dots arranged on a conical surface so that, when reflected from a test surface, it forms an ordered set of circular dots if the surface is perfect. Any deviation from this geometry is indicative of surface defects. To demonstrate that the corneal topographer provides reliable results on the topography of the human cornea, in this work, we set out to perform a calibration of the corneal topographer using a reference sphere with geometric parameters 7.8 mm radius and 12 mm diameter. We use a normal iterative method to reconstruct the surface shape and obtain the corneal topography.
In this project we propose a new corneal topographer that improves the accuracy of measurement from previous versions, by gathering all those details that made them to have great accuracy. The corneal topographer uses the null-screen method which is based on the idea that a reflected image in a surface contains information about the form of the reflective surface. The topographer uses a long cone, and it is aimed to evaluate corneas removing the symmetry of revolution of the algorithms. At first, the corneal topographer is utilized in a spheric reference surface, where the results obtained show that the radio of the reconstructed surface varies 0.11 % from the radio of the tested surface. This project is still in process since the evaluation algorithms must be adapted to evaluate corneas without symmetry of revolution. Keywords: null screen, corneal topography, topographic maps.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.