Corneal topography, also known as photokeratoscopy or videokeratography, is a non-invasive medical imaging technique for mapping the anterior curvature of the cornea, the outer structure of the eye.

Since the cornea is normally responsible for some 70% of the eye's refractive power,[1] its topography is of critical importance in determining the quality of vision and corneal health.

In either type, light is focused on the anterior surface of the patient's cornea and reflected back to a digital camera at the device.

The French ophthalmologist Louis Émile Javal incorporated the rings in his ophthalmometer and mounted an eyepiece which magnified the image of the eye.

[3] In 1896, Allvar Gullstrand incorporated the disk in his ophthalmoscope, examining photographs of the cornea via a microscope and was able to manually calculate the curvature by means of a numerical algorithm.

However, prices have fallen substantially over time, bringing corneal topographs into the budget of smaller clinics and increasing the number of patients that can be examined.

For example, the KISA% index (keratometry, I-S, skew percentage, astigmatism) is used to arrive at a diagnosis of keratoconus, to screen the suspect keratoconic patients and analyse the degree of corneal steepness changes in healthy relatives.

[6] Nevertheless, topography in itself is a measurement of the first reflective surface of the eye (tear film) and is not giving any additional information beside the shape of this layer expressed in curvature.