Active clinical trials for "Refractive Errors"

Primary objective of our study is to develop and validate an internet-based digital near and intermediate-vision reading test in the greek language.

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 the study is to compare the final glasses prescription based on refraction obtained with SVOne device to the final prescription obtained via subjective manifest refraction.

A holographic optical coherence tomography (H-OCT) setup is used to detect the wavefront by means of phase reconstruction.

To compare the prediction error of ORA vs formula for post-LASIK cataract patients when PanOptix IOL was implanted. Using post-operative outcomes to determine if preoperative IOL calculations, including Barrett TK, Barrett Universal II, Hill RBF, ASCRS post-refractive calculator, or intraoperative aberrometry is more accurate when the two methods disagree in patients who have had previous refractive surgery undergo cataract surgery.

In this study, the investigators aim to perform a prospective, randomized controlled study to compare the myopia development between children using myopia prediction algorithm and children without using myopia prediction algorithm.

In this study, the investigators aim to perform a prospective, randomized controlled study to compare the myopia development between myopia children using myopia prediction algorithm and myopia children without using myopia prediction algorithm

The two main objectives of this study are to demonstrate safety and effectiveness of implanting the PanOptix Trifocal IOL in patients who have had previous myopic Lasik. The primary objectives to demonstrate clinical safety will be the quality of vision questionnaire (QUVID) which will demonstrate the patient's perception of halos, glares, and starbursts before and after the implantation of the trifocal IOL. The primary objective to demonstrate clinical effectiveness will be done by measuring visual outcomes at distance, intermediate, and near. In addition, the patients will also fill out the spectacle independence questionnaire (IOLSAT Questionnaire) to determine their level of glasses independence postoperatively. In addition, at the conclusion of the study the patient will also fill out a patient satisfaction survey.

Conductive keratoplasty (CK) had shown to be a safe and effective procedure for the treatment of low to moderate hypeopia. It had been approved by the U.S. Food and Drug Administration (FDA) to treat presbyope in early 2004. CK appeals to both surgeons and patients as it avoids the need for flap creation, the use of high intraocular pressure (IOP), or tissue ablation. It utilizes "blended vision" rather than the true monovision used with laser in situ keratomileusis (LASIK), which patients tolerate more readily. There is very little reported research about the induction of wavefront aberration by CK. The symptomatology of high order aberrations (HOA) and the way individual Zernike functions were correlated with visual acuity, contrast sensitivity, visual symptoms. This study measured the HOA created by surgically induced myopic shift via CK and LASIK in an effort to better understand the phenomena of regression, multifocality, pseudo-accommodation and monovision.

Measuring parameters of anterior segment of the eye accurately is important for diagnosing variety of diseases and for cataract surgeries, glaucoma, refractive surgeries and post-operative follow-up. One of the anterior segment parameters is the anterior chamber depth. The anterior chamber depth (ACD) measurement provides valuable information in different fields in ophthalmology. Firstly, it is important for the new theoretical biometric formulas used to calculate the power of intraocular lenses (IOLs) .Secondly, phakic IOL implantation requires precise ACD measurement for both surgical planning and IOL power calculation. Thirdly, the ACD is also implicated as a screening risk factor for glaucoma. Additionally, precise ACD measurement is thought to be important to the accurate determination of the optic zone ablation diameter for keratorefractive surgery, as well as for the analysis of postoperative ACD changes. Different technologies are used in measurement of the anterior chamber depth Such as pentacam and iol maste