In a regular vision examination, the shape of the cornea is determined using a keratometer. This instrument is able to measure only the central area (one-third the full extend of the cornea) and therefore is limited in detecting corneal problems outside this zone.
Corneal topography uses a video system to take a picture of the entire cornea, and then applies a complex mathematical analysis of that picture to contruct a map of the shape of the entire cornea.
The Vision Institute uses corneal topography in the care of patients with Keratoconus or other corneal disorders.