الفهرس Only 14 pages are availabe for public view
 |  | from | 223 |  |  |
| | | from | 223 | | |
Abstract
The key to proper treatment is proper diagnosis and evaluation of regular astigmatism. This can be achieved clinically by refraction which measures the total amount of astigmatism of the optical system of the eye that is present in the pupillary zone, as would be corrected by a spectacle lens. Other devices for diagnosis include, keratometry which uses four reflected points (or two pairs) located at the center of the cornea, Placido disc imaging using Placido’s disk which is a painted disk of alternating black and white rings reflected in the cornea. The rings are projected onto the cornea and a virtual image is created slightly behind the cornea. The curvature of the cornea could be determined from comparison of photographs of the rings against standardized images, Raster stereography where an image is projected onto the corneal surface rather than reflected by it. The image then is digitized and analyzed by a computer imaging system. The data obtained from analysis of these images are displayed in easily understood formats, three dimensional topography (AstraMax) uses a three dimensional grid system rather than using a Placido disc, slit scanning topography, Scheimpflug imaging (pentacam), Ultrasound digital topography (Artemis), Interference fringe techniqueand and Fourier Transform Profilometry