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.

Purpose: To determine the origin of the wavefront aberration as measured in eyes fitted with diffractive intraocular lenses (IOLs). Methods: Wavefront aberration was measured by Shack-Hartmann aberrometry in 2 eyes fitted with diffractive bifocal contact lenses and 10 eyes implanted with Acrysof ReSTOR multifocal IOLs. Results: Problems were encountered as a result of the multiple wavefronts generated by the diffractive lenses and their dependence on wavelength. These led to ambiguities in the positions of the Shack-Hartmann spot images and in the form of the derived wavefronts. Conclusions: Aberrometry may not provide reliable information on the wavefront aberration associated with either the distance or near power of diffractive IOLs. [ J Refract Surg . 2008;24:280–286.]

Concurrent measurements of steady‐state accommodation response/stimulus curves and of pupil diameter were made in groups ( n = 20) of young, adult myopes [age (mean ± SD) 23.1 ± 4.5 years, mean‐sphere error (MSE) −3.06 ± 2.35 D, range −0.60 to −8.54 D] and emmetropes (mean age 25.3 ± 5.7 years, mean MSE −0.07 ± 0.26 D, range −0.50 to +0.50 D). The aim of this study was to explore the possibilities that pupil diameters with relaxed accommodation were larger, and that accommodative miosis was weaker, in the myopic group. Such behaviour would lead to relatively greater degradation of the retinal images in the myopic group, even though aberrations at constant pupil diameter and dioptric accommodative lags in the two groups were the same: this might result in excessive axial growth and further myopia development. No evidence for any systematic refractive dependence of pupillary characteristics or accommodative responses was found. Interestingly, those subjects whose response/stimulus curves had a higher slope tended to display greater accommodative miosis, irrespective of their refractive error.