Development of an in vitro model to study the biological effects of blinking.

Purpose: To develop a mechanical model in which a contact lens is swept over ocular surface cells under conditions that mimic the force and speed of the blink, and to investigate the resulting biological changes.

Methods: A computer controlled mechanical instrument was developed to hold a dish containing 3D cultured stratified human ocular surface epithelial cells, across which an arm bearing a contact lens was swept back and forth repeatedly at a speed and force mimicking the human blink. Cells were subjected to repeated sweep cycles for up to 1 h at a speed of 120 mm/s with or without an applied force of 19.

Predicting Accommodative Response Using Paraxial Schematic Eye Models.

Purpose: Previous ultrasound biomicroscopy (UBM) studies showed that accommodative optical response (AOR) can be predicted from accommodative biometric changes in a young and a pre-presbyopic population from linear relationships between accommodative optical and biometric changes, with a standard deviation of less than 0.55D. Here, paraxial schematic eyes (SE) were constructed from measured accommodative ocular biometry parameters to see if predictions are improved.

Distortion Correction of Visante Optical Coherence Tomography Cornea Images.

Purpose: Quantitative biometry measurements from uncorrected anterior segment optical coherence tomography (AS-OCT) images are inaccurate because of spatial and optical distortions. Prior reported distortion correction equations for the Visante AS-OCT were not reproducible. The goal was to calculate the distortions and provide equations to correct corneal parameters for the Visante AS-OCT to get a central corneal radius of curvature from young and older subjects.

Prediction of accommodative optical response in prepresbyopic subjects using ultrasound biomicroscopy.

Purpose: To determine whether relatively low-resolution ultrasound biomicroscopy (UBM) can be used to predict the accommodative optical response in prepresbyopic eyes as well as in a previous study of young phakic subjects, despite lower accommodative amplitudes.

Setting: College of Optometry, University of Houston, Houston, USA.

Design: Observational cross-sectional study.

Can ultrasound biomicroscopy be used to predict accommodation accurately?

Purpose: Clinical accommodation testing involves measuring either accommodative optical changes or accommodative biometric changes. Quantifying both optical and biometric changes during accommodation might be helpful in the design and evaluation of accommodation restoration concepts. This study aims to establish the accuracy of ultrasound biomicroscopy (UBM) in predicting the accommodative optical response (AOR) from biometric changes.

Defining the ideal femtosecond laser capsulotomy.

Purpose: We define the ideal anterior capsulotomy through consideration of capsular histology and biomechanics. Desirable qualities include preventing posterior capsular opacification (PCO), maintaining effective lens position (ELP) and optimising capsular strength.

Methods: Laboratory study of capsular biomechanics and literature review of histology and published clinical results.

Objective measurement of accommodative biometric changes using ultrasound biomicroscopy.

Purpose: To demonstrate that ultrasound biomicroscopy (UBM) can be used for objective quantitative measurements of anterior segment accommodative changes.

Setting: College of Optometry, University of Houston, Houston, Texas, USA.

Design: Prospective cross-sectional study.

Pharmacologically and Edinger-Westphal stimulated accommodation in rhesus monkeys does not rely on changes in anterior chamber pressure.

This study was undertaken to understand the role of anterior chamber pressure (ACP) during pharmacological and Edinger-Westphal (EW) stimulated accommodation in anesthetized monkeys. Experiments were performed on one iridectomized eye each of 7 anesthetized adolescent rhesus monkeys. Accommodation was induced by EW stimulation (n = 2) and intravenous administration of 0.

Comparison between carbachol iontophoresis and intravenous pilocarpine stimulated accommodation in anesthetized rhesus monkeys.

Rhesus monkeys are an animal model for human accommodation and presbyopia and consistent and repeatable methods are needed to stimulate and measure accommodation in anesthetized rhesus monkeys. Accommodation has typically been pharmacologically stimulated with topical pilocarpine or carbachol iontophoresis. Intravenous (i.

Long-term reproducibility of Edinger-Westphal stimulated accommodation in rhesus monkeys.

If longitudinal studies of accommodation or accommodation restoration procedures are undertaken in rhesus monkeys, the methods used to induce and measure accommodation must remain reproducible over the study period. Stimulation of the Edinger-Westphal (EW) nucleus in anesthetized rhesus monkeys is a valuable method to understand various aspects of accommodation. A prior study showed reproducibility of EW-stimulated accommodation over 14 months after chronic electrode implantation.

Advances in lens implant technology.

Cataract surgery is one of the oldest and the most frequent outpatient clinic operations in medicine performed worldwide. The clouded human crystalline lens is replaced by an artificial intraocular lens implanted into the capsular bag. During the last six decades, cataract surgery has undergone rapid development from a traumatic, manual surgical procedure with implantation of a simple lens to a minimally invasive intervention increasingly assisted by high technology and a broad variety of implants customized for each patient's individual requirements.

Quantification of age-related and per diopter accommodative changes of the lens and ciliary muscle in the emmetropic human eye.

Purpose: To calculate age-related and per diopter (D) accommodative changes in crystalline lens and ciliary muscle dimensions in vivo in a single cohort of emmetropic human adults ages 30 to 50 years.

Methods: The right eyes of 26 emmetropic adults were examined using ultrasonography, phakometry, anterior segment optical coherence tomography, and high resolution magnetic resonance imaging. Accommodation was measured both subjectively and objectively.

Manipulation of intraocular pressure for studying the effects on accommodation.

A reliable experimental system in which IOP can be manipulated or a rapid IOP change can be induced while simultaneously and continuously measuring IOP and the ocular accommodative changes would be useful for understanding the physiological effect of intraocular pressure (IOP) on the accommodative mechanism. In this study, an IOP perfusion and recording system was developed and tested using 13 enucleated pig eyes. The vitreous chamber of the pig eyes was cannulated with a needle connected to two fluid reservoirs at different heights.

Meta-analysis of sex differences in presbyopia.

Purpose: Uncorrected presbyopia is a significant cause of visual disability globally. Greater comprehension of the etiology of presbyopia and its contributing factors among medical and vision care providers could lead to changes in correction methods and account for sex differences in near-vision requirements.

Methods: A meta-analysis was performed using nine cross-sectional studies that provided sufficient data to compare the prevalence and magnitude of presbyopia among men and women.

Reproducibility of carbachol stimulated accommodation in rhesus monkeys.

Approaches are being explored to restore accommodation to the presbyopic eye. Some of these approaches can be tested in monkeys by stimulating accommodation in various ways including using carbachol iontophoresis. Knowledge of the repeatability of carbachol iontophoresis stimulated accommodation in the monkey phakic eye is necessary to understand the variability of this method of evaluating accommodation.

Full-field accommodation in rhesus monkeys measured using infrared photorefraction.

Purpose: Full-field photorefraction was measured during accommodation in anesthetized monkeys to better understand the monkey as a model of human accommodation and how accommodation affects off-axis refraction.

Methods: A photorefraction camera was rotated on a 30-cm-long rod in a horizontal arc, with the eye at the center of curvature of the arc so that the measurement distance remained constant. The resistance of a potentiometer attached to the rotation center of the rod changed proportionally with the rotation angle.

Accuracy and resolution of in vitro imaging based porcine lens volumetric measurements.

There is considerable interest in determining lens volume in the living eye. Lens volume is of interest to understand accommodative changes in the lens and to size accommodative IOLs (A-IOLs) to fit the capsular bag. Some studies have suggested lens volume change during accommodation.

Static and dynamic accommodation measured using the WAM-5500 Autorefractor.

Purpose: This study was undertaken to compare static and dynamic accommodation measurements using the Grand Seiko WR-5500 (WAM) in young, phakic subjects.

Methods: Fifteen subjects, aged 20 to 28 years (23.8 ± 0.