Eye examination. Screen display of a patient's eye during corneal topography measurement. In corneal topography, a device projects bright rings onto the eye, which are reflected in its surface. By studying the reflection, an accurate model can be built up of the shape of the patient's cornea. The cornea is the front part of the eye that covers the iris and pupil. It is responsible for the majority of light focusing, with only fine focusing being done by the lens. Defects in the shape of the cornea can lead to a wide range of focusing disorders. These can be treated by surgery or by the wearing of tailored contact lenses or spectacles.