Active clinical trials for "Astigmatism"

Aim of this study is to gain a better understanding of the diurnal changes of the cornea to improve toric IOL power calculations.

This study aims to assess the rotational stability of the new collameric Nanoflex toric intraocular lens (T-IOL) by STAAR inserted in astigmatic patients after cataract surgery. The purpose of this study is also to determine whether the use of a toric intraocular lens (T-IOL) improves visual acuity.

This study is to compare the contrast sensitivity function and neural response to gratings before and after the orientation discrimination task in the astigmatism or amblyopia patients.

In this study, the investigators employed Visante-OCT (Carl Zeiss, USA), an anterior chamber optical coherence tomography, to monitor the change of anterior chamber dimensions. These data were correlated to anterior and posterior curvature changes collected with the Oculus Pentacam (Oculus Inc., Germany), a corneal topographer based on rotating Scheimpflug principle. To minimize the effect of convergence and excyclotorsion during examination, topical cycloplegic medication was used. The investigators hypothesized that if there is a link between ciliary muscle contraction and cornea curvature, installation of cycloplegic should result in widening of anterior chamber angle to angle distance and flattening of the cornea curvature data.

To determine the effectiveness of correcting astigmatism by laser refractive surgery by a vectorial astigmatism outcome analysis that uses 3 fundamental vectors : target induced astigmatism vector ( TIA) , surgically induced astigmatism vector , and difference vector , as described by Alpins method.

The purpose of this combined retrospective and prospective chart review analysis is to investigate the safety, efficacy, and predictability obtained via Laser-Assisted In Situ Keratomileusis (LASIK) and Advanced Surface Ablation (ASA) over a wide range of refractive errors The working hypothesis is that there will be no difference in clinical outcomes between patients treated with LASIK or ASA.

Development of a validated computer-based instrument (software program) for the assessment of intermediate visual acuity.

This clinical study is an open, controlled, prospective, single center, single-surgeon, post-market-clinical-follow-up study to evaluate the long-term (18 months) effectiveness of the femtolaser-assisted astigmatic keratotomy.

The magnitude of posterior corneal astigmatism was considered negligible due to the smaller difference in the refractive index between the cornea and the aqueous . though ,neglecting the posterior corneal astigmatism lead to errors during calculation of the toric iols (over or under estimation ) . so we aim to determine the percentage of contribution of posterior corneal astigmatism to total corneal astigmatism in a sample of Egyptian population using scheimpflug imaging (Pentacam ).

MAIN OBJECTIVE: To assess the influence of residual astigmatism on visual acuity in the different lens foci in patients operated on for cataracts with a trifocal intraocular lens implant. SECONDARY OBJECTIVE: To study the influence of residual astigmatism on the visual quality of the patient in the far focus and to determine if there are differences of affectation in the two study groups.