Automated corneal topography: computerized analysis of photokeratoscope images

The analysis of corneal topography has recently become popular, mainly as a consequence of the rapid development of refractive surgery techniques. To date, computer-assisted evaluation of photokeratoscope pictures has been the most popular method used to assess corneal topography. The processing system described previously by other authors requires hand-digitizing of the photokeratoscope pictures and therefore the constant presence of an operator for a considerable amount of time. We have introduced the use of a video camera to digitize the photokeratoscope images, making the processing automatic and quicker. Moreover, precision glass spheres have been used to calibrate the system in order to minimize the intrinsic errors even further. The data obtained from the computerized analysis are presented in three different ways. Besides having the numerical values in diopters, corneal maps with various shades of grey are used, together with the quantitative, three-dimensional representation of corneal astigmatism. An automated system for the analysis of corneal topography was tested for both experimental models and clinical conditions. It was easy to use and showed high precision (less than 1% error when processing photographs of precision glass spheres).