The Prism Adaptation Study (PAS)

September 16, 2009 updated by: National Eye Institute (NEI)

To determine whether the preoperative use of prisms in eyeglasses can improve the outcome of surgery for acquired esotropia, a type of strabismus.

To determine whether patients who respond to prism adaptation by developing a new stable angle of -deviation have a better surgical result than do patients who do not respond to prism adaptation.

To determine whether patients who respond to prism adaptation are more accurately corrected by operating for the prism-adapted angle or the original angle of deviation.

To determine the usefulness of certain input variables (e.g., age at the time of surgery, size of the deviation, visual acuity, binocular function, refractive error) in predicting which patients are more likely to benefit from prism adaptation.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Acquired esotropia (crossed eyes that develop after a child reaches the age of 6 months) accounts for 25 percent of all patients with misaligned eyes. Surgery to correct esotropia is done primarily to attain functional use of the two eyes together. The cosmetic aspect of the surgery is secondary. In 40 to 50 percent of cases, more than one operation is needed to accomplish the primary goal, and in some cases even three and four operations are needed.

Preliminary studies from two eye care centers reported that the use of prisms on eyeglasses for about a month before surgery led to good results after a single operation in more than 90 percent of patients. These uncontrolled preliminary studies pointed to the need for a multicenter, randomized, controlled clinical trial designed to prove or disprove scientifically the beneficial effect of prisms.

The Prism Adaptation Study was a double randomization trial involving 286 patients. Three-fifths of the patients were randomly selected for prism adaptation before surgery. Of the patients who responded to the prisms, one-half were randomly selected to have surgery based on the amount of prism required to stabilize the deviation, and the other half had surgery based on the amount of esotropia originally measured. Patients who did not respond to the prisms also had surgery based on the amount of esotropia measured, as did the two-fifths of the patients who did not undergo prism adaptation.

Patients were examined postoperatively at 1 week, 1 month, 3 months, 6 months, and 1 year. An independent examiner, masked to the treatment assignment, evaluated the patient at the 6-month followup. The results were analyzed to determine whether the outcome was better in patients who underwent prism adaptation or in those who underwent conventional treatment. Because the examiner did not know what type of treatment a patient had received, he or she would have no bias in evaluating the results.

Study Type

Interventional

Phase

  • Phase 3

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

3 years and older (Child, Adult, Older Adult)

Accepts Healthy Volunteers

N/A

Genders Eligible for Study

All

Description

An eligible male or female must have been age 3 years or older (adults were included) and must have had esotropia that occurred at age 6 months or older, with no history of previous eye muscle surgery.

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: Randomized

Collaborators and Investigators

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

Publications and helpful links

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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

March 1, 1984

Study Completion (Actual)

May 1, 1989

Study Registration Dates

First Submitted

September 23, 1999

First Submitted That Met QC Criteria

September 23, 1999

First Posted (Estimate)

September 24, 1999

Study Record Updates

Last Update Posted (Estimate)

September 17, 2009

Last Update Submitted That Met QC Criteria

September 16, 2009

Last Verified

September 1, 2009

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • NEI-20

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.

Clinical Trials on Esotropia

Clinical Trials on Prisms in Eyeglasses

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