The contribution of the posterior surface to the coma aberration of the human cornea.

Scheimpflug imaging was used to measure in six meridians the shape of the anterior and posterior cornea of the right eye of 114 subjects, ranging in age from 18 to 65 years. Subsequently, a three-dimensional model of the shape of the whole cornea was reconstructed, from which the coma aberration of the anterior and whole cornea could be calculated. This made it possible to investigate the compensatory role of the posterior surface to the coma aberration of the anterior corneal surface with age. Results show that, on average, the posterior surface compensates approximately 3.5% of the coma of the anterior surface. The compensation tends to be larger for young subjects (6%) than for older subjects (0%). This small effect of the posterior cornea on the coma aberration makes it clear that for the coma aberration of the whole eye, only the anterior corneal surface and the crystalline lens play a role. Consequently, for the design of an intraocular lens that is able to correct for coma aberration, it would be sufficient to only take the anterior corneal surface into account.