View clinical trials related to Refractive Errors.
Filter by:The purpose of this study is to evaluate the performance of two commercially-available silicone hydrogel contact lenses in normal and low humidity environments after at least 7 days of wear.
The purpose of this study is to evaluate the incidence of ocular discomfort device-related adverse events with DAILIES TOTAL1® with UV Absorber (DT1 UV) contact lenses compared with current DAILIES TOTAL1® (DT1) contact lenses.
Prospective, multicenter, bilaterally-treated, open-label, non-randomized clinical trial.
Myopia has emerged as a major health issue in east Asia, because of its increasingly high prevalence in the past few decades (now 80-90% in school-leavers), and because of the sight-threatening pathologies associated with high myopia, which now aff ects 10-20% of those completing secondary schooling in this part of the world. Similar, but less marked, changes are occurring in other parts of the world. The higher prevalence of myopia in east Asian cities seems to be associated with increasing educational pressures, combined with life-style changes, which have reduced the time children spend outside.
The Baltimore Reading and Eye Disease Study (BREDS) is a two year study to determine the prevalence of vision problems in an early school age population with reading difficulty. Comprehensive vision and reading tests will be administered to 400 students at participating schools in the Baltimore City Public School system. A secondary goal is to examine the impact of vision treatment on reading performance. Children with refractive error or convergence insufficiency will be provided treatment free of charge. The investigators will evaluate the impact that the treatment has on vision function and reading performance.
This will be an up to six months, subject-masked, contralateral, parallel-group, randomised, daily wear study. All subjects will wear the Test lens in one eye and the Control lens in the other eye. Data from the first four weeks of Test and Control lens exposure will be used for the FDA 510 (k) submission.
The purpose of this study is to validate the safety and effectiveness of treating myopia (short-sightedness) higher than -10D using small incision lenticule extraction (SMILE) with the VisuMax femtosecond laser.
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.