Corneal topography is the measurement of the surface of the cornea, a single layer of epithelial cells above the connective tissue in the iris. As the cornea is responsible for refracting light into the lens of the eye, minor changes in its uniform surface can lead to vision loss. With a corneal topography system, the user views the patient’s cornea upon which are projected up to 23 placid rings – much like the rings that represent elevation on a topographical map. Anomalous bumps or pits are represented as irregularities in the shape of the rings, or the spacing between them. These systems employ visual or IR light sources and three-dimensional digital displays of the cornea, entire optical system or just the internal regions. They permit working distances of up to 70mm, and accuracy of ± .05mm. The customer should seek analyzers with capabilities tailored to specific applications, such as fitting contact lenses, screenings for cataract surgery or postoperative evaluations.