Photorefractive Keratectomy for Severe Anisometropia and Isoametropia Associated With Amblyopia

June 28, 2023 updated by: Evelyn Paysse, Baylor College of Medicine

Photorefractive Keratectomy for Anisometropic and Isoametropic Amblyopia in Children Refractory to Conventional Treatment

Photorefractive keratectomy (PRK) with excimer laser has been used successfully to treat myopia, hyperopia, and astigmatism in adults for over 35 years. Children with high refractive errors that go untreated will develop severe amblyopia. PRK can normalize high refractive errors and potentially improve the visual acuity in affected children. The purpose of this study is to investigate whether children with high anisometropia or isoametropia with amblyopia that are nonresponsive to standard therapy and receive PRK develop better longterm visual acuity.

Study Overview

Detailed Description

Anisometropia is a condition in which one eye has a significantly different refractive error from the other and commonly leads to the development of refractive amblyopia in the affected eye. High isoametropia is the condition in which both eyes have high refractive error and commonly leads to bilateral refractive amblyopia if untreated. Amblyopia is the condition in which vision does not develop fully in the brain due to disuse or misuse of one or both eyes. Typically, in high anisometropia, a contact lens in the eye with the stronger refractive error and/or glasses must be used to correct the refractive error. Commonly, infants and children with this condition refuse to wear the contact lens or glasses because the other eye sees normally. There are other problems in treating high anisometropia with glasses. One is aniseikonia, the condition of image size disparity between the two eyes. This causes difficulty for the brain of the affected person to fuse the images from the two eyes because the image from one eye is much larger than that from the other eye. This results in asthenopia (eye fatigue) and sometimes even diplopia. If the anisometropia is severe, significant amblyopia will result in the eye with the stronger refractive error and, if not treated at an early age, permanent and potentially severe vision loss will result.

In high isoametropia, contact lenses or glasses must likewise be used in order for normal vision to develop. Most children with isoametropia will wear glasses well because they cannot see well without them. By contrast, children with developmental delays, chromosomal abnormalities, autism, or attention deficit hyperactivity disorder and high isoametropia very commonly will not wear the needed refractive correction due to strong tactile aversion to anything touching their face or head. If the refractive error is high, significant bilateral (isoametropic) amblyopia will result and, if not treated at an early age, permanent and potentially severe vision loss will result.

PRK can normalize high refractive errors and potentially reduce or eliminate the amblyopia in affected children. The purpose of this study is to investigate whether children with high anisometropia or isoametropia with amblyopia that are nonresponsive to standard therapy and receive PRK develop better longterm visual acuity. Secondary outcomes are stability of refractive correction, and corneal health.

Study Type

Interventional

Enrollment (Estimated)

200

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

    • Texas
      • Houston, Texas, United States, 77030
        • Texas Children's Hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

8 months to 15 years (Child)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:.

  • Children aged 2 to 17 with significant anisometropia or isoametropia and amblyopia that have failed traditional treatment for at least 6 months.
  • Anisometropic group:
  • The anisometropia must be at least 3.00 diopters.
  • The amblyopic eye best corrected visual acuity must be at least 2 lines worse than the fellow eye in verbal children
  • Isoametropic group
  • Myopia must be at least -4.00 diopters in both eyes
  • Hyperopia must be at least +4.00 diopters in both eyes
  • Astigmatism must be at least +2.50 diopters in both eyes.

Exclusion Criteria:

  • History of significant corneal abnormality that, in the investigator's opinion, may limit visual rehabilitation.
  • History of known collagen disorder
  • History of known corneal ectasia
  • History of previous herpes simplex keratitis
  • Corneal thickness of less than 450u

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Other: Photorefractive keratectomy
The children will undergo PRK in the affected eye(s) using previously derived formulas for PRK.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Visual acuity
Time Frame: 10 years
Snellen equivalent
10 years

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Refractive error
Time Frame: 10 years
cycloplegic refraction
10 years
Corneal clarity
Time Frame: 10 years
slit lamp exam
10 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Investigators

  • Principal Investigator: Evelyn Paysse, MD, Baylor College of Medicine

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 1, 2001

Primary Completion (Estimated)

August 1, 2028

Study Completion (Estimated)

October 1, 2028

Study Registration Dates

First Submitted

July 19, 2018

First Submitted That Met QC Criteria

July 26, 2018

First Posted (Actual)

August 2, 2018

Study Record Updates

Last Update Posted (Actual)

June 29, 2023

Last Update Submitted That Met QC Criteria

June 28, 2023

Last Verified

June 1, 2023

More Information

Terms related to this study

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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