Corneal Topography for Slit Lamps

摘要

In order to provide automatic measurements of the radii of curvature of the cornea, having precision comparable to corneal topographers that are available on the market, we have developed an automatic topographer module for slit lamp.The system consists of projecting 22 Placido's rigns displayed in a precise circle at the examined cornea. The reflected image of these light rings are captured and the displacement and deformation of the rings are analyzed in order to provide the radii of curvature of the cornea, as well as the associated astigmatism. The result is presented in 1.2s in a OQO micro computer. Measurements in the range of 25D - 81D can be obtained and a self calibration system has been specially designed in order to keep the system calibrated in the slit lamp.An infra-red sensor indicates automatically which eye is being examined. The clinician may use the PC's mouse or either press a button (from the joystick of the slit lamp or using a pedal under the examining table) to obtain the keratometry after focusing the slit lamp either by the eyepieces of the microscope or by the PC's monitor.Volunteer patients have been submitted to the system and preliminary results show that our system has a correlation factor of 0.95 with the commercially available topographers (Eyetec CT 2000 and Humphrey - Atlas 995 - CZM).The system's nominal precision is 0,0025mm for the radii of curvature and 1° for the associated axis.