Prevalence of interocular symmetry in corneal astigmatism and the possible influence of age, sex and refractive error.

Purpose: The aim of this study was to investigate, using a power vector approach, whether corneal astigmatism follows a mirror symmetry pattern considering both the magnitude and axis, and whether age, sex and spherical equivalent refractive error can influence the pattern.

Methods: The IOLMaster 700 optical biometer was used to measure the radii of curvature of the anterior corneal surface. Refractive error was determined by non-cycloplegic subjective refraction.

Optical characterization of a manual tunable lens for eye-care applications.

The popularity of focus tunable lenses has increased in the last decade. In this study we present an experimental optical characterization of a commercially available manually tunable lens to describe its behavior regarding optical aberrations, expressed in terms of Zernike coefficients, under different laboratory conditions. Measurements were performed by using a Shack-Hartmann aberrometer, and four different experiments were carried out in order to assess 1) the lens stability in time for a given temperature, 2) the temporal response of the lens, 3) the behavior of the lens when changing the room temperature, and 4) the possible influence of gravity on the lens performance according to its mounting orientation.

Revisiting Javal's rule: a fresh and improved power vector approach according to age.

Purpose: The scientific community has established Javal's rule as a model linking refractive (RA) and keratometric (KA) astigmatism since its appearance more than 100 years ago. The aim was to improve the accuracy of this relationship according to subject's age by applying the power vector analysis. Posterior corneal curvature has also been studied.

Vecto-keratometry: determination of anterior corneal astigmatism in manual keratometers using power vectors.

Background: A new keratometric routine that employs power vector management for manual keratometers is described. This study evaluates the agreement of the new proposed keratometric technique with the classical one.

Research Design And Methods: The applicability of a new keratometric routine was verified using Helmholtz's and Javal's keratometers.