Single-Shot Deflectometry for Precise Cornea Measurement
At the Institute of Optics, Information and Photonics, Friedrich-Alexander-University Erlangen Nuremberg, we have introduced an innovative application of phase-measuring deflectometry (PMD) for precise measurement of the human cornea. PMD, a well-established technique for measuring specular surfaces, has been adapted to overcome the unique challenges posed by cornea metrology.
We addressed two key issues: the large angular range of the cornea and the potential for motion blur during measurement. By employing a special geometry with a large screen placed close to the eye and a small mirror to direct reflected light to the camera, we achieved an impressive angular slope range of ±27 degrees. To eliminate motion blur, a single-shot deflectometry method was implemented, allowing for measurement within a single exposure.
Pre-distortion of the projected fringe pattern was crucial in obtaining a regular, high-contrast reflected image suitable for accurate analysis. Our preliminary results demonstrate successful measurement of corneal topography over a 7 mm diameter, with a refractive power ranging from 34 to 45 diopters. This groundbreaking adaptation of PMD promises to provide ophthalmologists with a valuable tool for detailed, pixel-dense corneal topography assessment.