PURPOSE Recent studies report that increased corneal edema because of contact lens wear under closed lids is associated with elevated Goldmann intraocular pressure (GAT IOP). We sought to assess whether the impact of postoperative corneal edema on GAT IOP would be similar and to determine the differential effect of different amounts of edema. METHODS The setting is a tertiary level cataract c...

Pterygium is a vascularized, invasive transformation on the anterior corneal surface that can be treated by Strontium-/Yttrium90 beta irradiation. Finite element modeling was used to analyze the biomechanical effects governing the treatment, and to help understand clinically observed changes in corneal astigmatism. Results suggested that irradiation-induced pulling forces on the anterior cornea...

OBJECTIVE To examine genetic influences for quantitative refraction. Spherical equivalent and its related binary traits of myopia and hyperopia are highly correlated within families. Many linkage regions have been reported for myopia, high myopia, and quantitative refraction. However, the measured phenotype of spherical equivalent is in large part dictated by the relationship between the underl...

OBJECTIVE To evaluate the effect of central corneal thickness (CCT), corneal curvature, and axial length on applanation tonometry in an in vivo study. METHODS In a masked, prospective clinical trial, we examined 125 eyes of 125 patients scheduled for cataract surgery. Corneal curvature was measured by means of keratometry and axial length by A-scan ultrasonography. By cannulating the anterior...

This study was designed to evaluate the correlation between corneal biomechanical and morphological data in healthy eyes, eyes that underwent myopic photorefractive keratectomy (PRK), keratoconus affected eyes, and keratoconus affected eyes that underwent corneal collagen crosslinking (CCC). Complete clinical eye examination of all eyes was followed by tomographic (Pentacam, Oculus, Wetzlar, Ge...

PURPOSE To determine the normal distribution of corneal diameter in a 40- to 64-year-old population and its association with other biometric components. METHODS In a cross-sectional population-based study, subjects were selected through multistage cluster sampling from the 40- to 64-year-old citizens of Shahroud in northern Iran. After obtaining informed consents, optometry tests including re...

In this paper, we derive a nonlinear equation of corneal asphericity (Q) using the tangential radius of curvature (rt) on every semi-meridian. We transform the nonlinear equation into the linear equation and then obtain the Q-value of corneal semi-meridian by the linear regression method. We find the 360 semi-meridional variation rule of the Q-value using polynomial function. Furthermore, we co...

This review of corneal topography has three sections: 1. a brief introduction to how corneal topography instruments work. A quantitative comparison of the relative accuracy of slope based and position based instruments is presented. 2. a summary of and commentary on the newly issued ANSI standards for corneal topography. 3. an examination of problems still facing corneal topography. OCIS codes:...

PURPOSE To highlight two cases of keratoconus with significant variations of corneal curvature during pregnancy that reversed several months after delivery. METHODS Case reports and literature review. RESULTS Two women experienced a significant decrease of corrected distance visual acuity during pregnancy. Evaluation of corneal topography by Scheimpflug imaging revealed transitory variation...