Refractive errors are by far the commonest cause of defective vision that must be looked for in any patient complaining of inability to see clearly. Topography is the science of accurate and detailed description of surface features. Its advantage ,is to detect any early changes on the corneal surface which cannot be detected by using other methods. Methods of assessment of corneal topography include: Placido’s disc, keratometer, keratoscope, pachymeter and computer-assisted videokeratography. Computer-assisted videokeratography combines concentric ring keratoscopy with analysis by computer programs to produce a high-resolution representation of corneal topography. Although the color-coded contour map provides a quantitative power at each point, interpretation of the pattern of colors is qualitative.