Corneal topographic map, like military map, uses the depth of color to represent the convexity and steepness of cornea. Generally, keratoconus has a special protrusion, which is used to eliminate the problem of keratoconus before laser surgery for myopia.
The examination of corneal topography mainly depends on the shape of cornea. In different operations or diseases, the purpose will be slightly different, mainly to exclude keratoconus and find out the cause of large astigmatism.