View clinical trials related to Refractive Errors.
Filter by:Corneal topography allows the measure of the radii of curvature and of the thickness of the cornea. It is essential for diagnosis in ophthalmology and allows to highlight corneal irregularities such as a keratoconus, or too thin corneas which are a contra-indication for laser refractive surgery. Several types of corneal topographers are commercially available. Some as the Orbscan(r), operate by analyzing the image of the patterns of a Placido disk associated with a light slit, allowing the collection of thousands of points of the anterior and posterior surface of the cornea. More recent systems such as the Pentacam(r) are based on automatic rotary cameras which capture images of the whole anterior segment of the eye. The aim of this study is to compare two topographs, the Pentacam(r) and the Orbscan(r) and, more specifically, the central corneal pachymetry measurements measured pre- and postoperatively.
In refractive surgery, stromal ablation depth is fundamental because it determines the thickness of the residual posterior wall. The posterior wall is an essential element that guarantees the refractive stability and the long term prevention of corneal ectasia after corneal refractive surgery. A minimum thickness of more or less 300 microns is universally accepted. Its calculation is based on well-known formulas, such as Munnerlynn ones. With the excimer laser platform last generation WaveLight® Allegretto® EX-500 of Alcon, a new treatment option called "wavefront optimized" is offered for myopia, astigmatism and hyperopia. The ablation profile has been developed to save stromal tissue consumption and to favor the quality of vision, by optimizing connections between the optical zone and the transition zone of the photoablation. Alongside the theoretical formulas, evaluation of the depth of ablation may be defined by differential ultrasonic pachymetry or by topographical analysis pre and postoperatively. The latter is currently the method of reference to assess the corneal thickness.
The purpose of this study is to evaluate the tear film evaporation of symptomatic soft contact lens wearers in the absence of contact lens wear and after at least 8 hours of contact lens wear.
The purpose of this study is to evaluate cholesterol sorption by Air Optix® Aqua lenses compared to ULTRA lenses after 30 days of wear.
The aim of this study is to assess the visual performance of multiple optimised prototype soft contact lens designs compared to commercially available contact lenses.
Dispensing Study for the Phenacite Project. The investigational test lens was not the final optical design and the study was not used for design validation.
The purpose of this study is to evaluate Clear Care® Plus compared to PeroxiClear™ for mean residual peroxide in used lens cases collected at Day 30.
The purpose of this study is to measure the coefficient of friction of three silicone hydrogel daily disposable contact lenses (1-DAY ACUVUE® TruEye®, MyDay™ and clariti® 1day) after 16 hours of wear.
The purpose of this study is to evaluate the functional vision of 2 daily disposable silicone hydrogel contact lenses using Time Controlled Visual Acuity (TCVA) measurements at high luminance and high contrast after 10+/-3 days of wear post 3 hour exposure to a reduced humidity environment.
The purpose of the study is to compare the investigational contact lens to a marketed contact lens. The study results were not used for design validation of investigational contact lens,