Comparison of Cross-cylinder and Conventional Photorefractive Keratectomy(PRK) in Correcting Medium-high Astigmatism

Tabriz University

Status and phase: Completed; Phase 3

Conditions: Astigmatism

Treatments: Procedure: photorefractive keratectomy (PRK)

Study type: Interventional

Funder types: Other

Identifiers

NCT00663923

86-43

Details and patient eligibility

About

The purpose of this study is to determine whether cross-cylinder approach is more effective than routine method in laser correction of astigmatism.

Full description

Both eyes of 50 patients(100 eyes) with medium-high compound myopic astigmatism and inclusion criteria,will be treated by photorefractive keratectomy (PRK) using excimer laser.It breaks chemical bonds within corneal stroma.It's wavelength is 193 nm that is in the ultraviolets range with high energy and very low tissue penetrance. The right or left eye of every patient would be allocated randomly to one of the study groups using RandList 1.1. In spite of recent advances in excimer laser machines and surgical techniques,correction of astigmatism is not more successful compared to myopia. In this study we will compare two methods of laser correction of astigmatism regarding to visual acuity,residual error and aberrations.

Enrollment: 50 patients

Sex: All

Ages: 20+ years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• >20 years of age
• refractive stability for at least one year
• regular and symmetric astigmatism of >1.5 diopters

Exclusion criteria

• corneal thickness<470 microns
• keratoconus or suspected keratoconus
• active ocular disease and systemic collagen disease

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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50 participants in 2 patient groups

cross-cylinder

Experimental group

Description:

In this technique the laser is programmed with the axis and amount of cylinder,so that the steepest meridian is flattened with central cylindrical ablation and the flattest meridian steepens with paracentral ablation

Treatment:

Procedure: photorefractive keratectomy (PRK)

single

Active Comparator group

Description:

In this technique ,cylinder is treated only on one meridian by performing an elliptical ablation to to flatten the steeper meridian to match the flatter meridian.

Treatment:

Procedure: photorefractive keratectomy (PRK)