Feasibility of intraoperative corneal topography monitoring during photorefractive keratectomy

PURPOSE: We propose a feasibility study of new corneal topography technology with the aim of monitoring intraoperative corneal topography during excimer laser photorefractive keratectomy. The PAR system measures corneal topography with single grid projection and triangulation but requires fluorescent fluid to be deposited on the corneal surface for shape extraction. We propose and demonstrate a novel corneal topography system based on structured incoherent visible light projection and triangulation that does not require addition of fluorescent fluid. METHODS: We used a binary liquid crystal spatial light modulator to display multiple fringe patterns onto the cornea. The depth accuracy of the corneal topography system was measured using a white reflected test sphere mounted on a micrometer translation stage. The performance of the corneal topography system was tested on 5 de-epithelialized swine eyes in vitro ablated with a VISX excimer laser. RESULTS: Depth accuracy on the test sphere was 0.5+/-0.75 microm over an area of 17.6 mm2. On de-epithelialized swine corneas, ablation at the apex of the cornea treated with an excimer laser was measured without addition of fluorescein. CONCLUSIONS: This new corneal topography system achieved an adequate level of accuracy on a test sphere.