Automatic measurements of the radius of curvature of the cornea in Slit Lamp

摘要

We have developed an automatic optical system attached to the Slit Lamp in order to provide automatic measurements of the radius of curvature of the cornea at low cost. The system consists of projecting a light ring as a target at the patient's cornea and the further analysis of the deformation of the target in order to obtain the radius of curvature as well as the axis of the associated astigmatism. The reflected image of the target is displayed in a PC's monitor and a dedicated developed software performs the analysis of the image, that provides the corneal keratometry. Also, the system is able to measure irregular astigmatism and the clinician is able to understand the behavior of the cornea's curvature radius in these regions by comparison of the graphical analysis of regular astigmatism that is generated by the software. There is no system commercially available which is able to measure irregular astigmatism, which is a very important feature for keratoconeous detection. The system is easy to use and it has a friendly software interface for the user. Measurements in volunteer patients have been made and the results that were obtained in the system, for the standard target ring, are in good agreement with commercial automatic and manual systems, presenting a correlation coefficient of 0,99347 and 0,97637, respectively regarding the radius of curvature and 0,96841 and 0,9568, respectively, regarding the axis. The system's precision is 0,005 mm for the curvature radius and 2* for the axis component.