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Manually Performed Limbal Relaxing Incisions vs Femtosecond Laser-guided Astigmatic Keratotomy

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Know the risks and potential benefits of clinical studies and talk to your health care provider before participating. Read our disclaimer for details. Identifier: NCT03264534
Recruitment Status : Not yet recruiting
First Posted : August 29, 2017
Last Update Posted : January 11, 2018
Information provided by (Responsible Party):
Ashraf Rashwan, Assiut University

Brief Summary:

Astigmatic keratotomy (AK) is used to treat numerous refractive disorders, including congenital astigmatism, residual corneal astigmatism at the time of or following cataract surgery, post-traumatic astigmatism, and astigmatism after corneal transplantation.

Within the past few years, much consideration has been given to an evolutionary variant of the procedure, the limbal relaxing incision (LRI). By moving the incision farther to the periphery, cataract surgeons can safely and predictably remediate mild to moderate amounts of regular astigmatism at the time of cataract surgery by performing this incisional technique.

Recent technological developments have shifted ophthalmologist's attention from manually created LRIs and astigmatic keratotomy procedures to femtosecond laser-guided procedures. Femtosecond lasers offer superior incisional accuracy and reproducibility coupled with minimal effects on collateral tissues, achieving levels of safety and reproducibility exceeding those of mechanical techniques. A major clinical application of the femtosecond laser is for creating arcuate incisions that have a precise and accurate length, depth, angular position, and optical zone.

Condition or disease Intervention/treatment Phase
Corneal Astigmatism Procedure: limbal relaxing incisions Procedure: astigmatic keratotomy Not Applicable

Detailed Description:

Pre-operative evaluation:

  1. Close examination of the peripheral cornea by slit lamb, particularly in the areas where the incisions will be placed.
  2. Fundus examination to exclude other causes of diminution of vision.
  3. IOP measure.
  4. Precise manifest refraction, uncorrected visual acuity and best corrected visual acuity by snellen's chart.
  5. Standard keratometry to confirm diopters of corneal astigmatism.
  6. Corneal Tomography (Pentacam).

Surgical procedures:

LRIs are performed using topical anesthesia. Patients are instructed to fixate on the microscope light. Before surgery, the steep meridian was identified with a marker dyed with methylene blue with the patient sitting up right. A diamond knife is set at a depth of 0.600 mm to 0.650 mm based on the peripheral pachymetric readings over the area of intended incision. The goal was a maximum reduction in astigmatism without overcorrection in with-the rule cases and with little overcorrection in against the rule cases. In the case of an overcorrection, the LRI can be sutured without creating any irregular astigmatism.

Performing femtosecond laser-guided astigmatic keratotomy requires the parameters of length, position, depth and distance from the visual axis where the incisions will be created. The depth of our incisions is 85% of the corneal pachymetry in the area of the incision. We have set our distance from the visual axis at 8 mm. This information is all downloaded onto the femtosecond laser. Then, we begin the surgical procedure by docking the laser onto the cornea. An overlay of the incisions is then visible on the surgical screen. After treatment, we bring the patient to the operating microscope and open the incisions with a Sinskey hook. By using low energy, the incisions do not have significant effect until they are opened.

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Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 80 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)
Primary Purpose: Treatment
Official Title: Manually Performed Limbal Relaxing Incisions vs Femtosecond Laser-guided Astigmatic Keratotomy for Correction of Corneal Astigmatism After Phacoemulsification
Estimated Study Start Date : March 2018
Estimated Primary Completion Date : April 2019
Estimated Study Completion Date : October 2019

Arm Intervention/treatment
Active Comparator: limbal relaxing incisions
Manually performed limbal relaxing incisions
Procedure: limbal relaxing incisions
Manually performed surgical procedure

Active Comparator: astigmatic keratotomy
femtosecond laser-guided astigmatic keratotomy
Procedure: astigmatic keratotomy
femtosecond laser guided surgical procedure

Primary Outcome Measures :
  1. Keratometric reading [ Time Frame: 1 week ]
    measured by Corneal Tomography (Pentacam)

Information from the National Library of Medicine

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Ages Eligible for Study:   21 Years to 65 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  1. patients who have undergo phacoemulsification.
  2. Clear cornea.
  3. Astigmatism from 1 diopter up to 4 diopters

Exclusion Criteria:

  1. corneal opacity.
  2. History of corneal surgery.
  3. Thin cornea.
  4. Other cause of diminution of vision rather than corneal astigmatism (eg: optic disc atrophy & maculopathy).
  5. Astigmatism less than 1 diopter and more than 4 diopters.

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Responsible Party: Ashraf Rashwan, Principal Investigator, Assiut University Identifier: NCT03264534     History of Changes
Other Study ID Numbers: 17200119
First Posted: August 29, 2017    Key Record Dates
Last Update Posted: January 11, 2018
Last Verified: August 2017
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Undecided
Plan Description: There is a possibility of using these data in another related study so i am not sure about the time of sharing the individual participant data

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Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No

Additional relevant MeSH terms:
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Refractive Errors
Eye Diseases