Feasibility of intraoperative corneal topography monitoring during photorefractive keratectomy

PURPOSE: We propose a feasibility study of new corneal topography technolog y with the aim of monitoring intraoperative corneal topography during excim er laser photorefractive keratectomy. The PAR system measures corneal topog raphy with single grid projection and triangulation but requires fluorescen t fluid to be deposited on the corneal surface for shape extraction. We pro pose 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 cornea l topography system was measured using a white reflected test sphere mounte d on a micrometer translation stage. The performance of the corneal topogra phy system was tested on 5 deepithelialized swine eyes tn vitro ablated wit h a VISX excimer laser. RESULTS: Depth accuracy on the test sphere was 0.5 +/- 0.75 mu m over an ar ea of 17.6 mm(2). On de-epithelialized swine corneas, ablation at the apex of the cornea treated with an excimer laser was measured without addition o f fluorescein, CONCLUSIONS: This new corneal topography system achieved an adequate level of accuracy on a test sphere.