Base-in Prism Spectacles for Intermittent Exotropia (IXT6)

Intermittent Exotropia Study 6: A Pilot Randomized Clinical Trial of Base-in Prism Spectacles for Intermittent Exotropia

The objective of this short-term, pilot randomized trial comparing spectacles with relieving prism to spectacles without prism is to determine whether to proceed to a full-scale, longer-term randomized trial. This decision will be based primarily on assessing the initial (8-week) response to prism by comparing treatment groups on the following outcomes:

• Mean distance intermittent exotropia (IXT) control score (the mean of 3 control scores) (primary outcome)
• The proportion of participants demonstrating a "treatment response," defined as ≥1 point improvement in the mean distance IXT control score without spontaneous exotropia during control testing (secondary outcome)
• The proportion of participants reporting adverse effects and good/excellent spectacle wear compliance

Study Overview

• Status: Completed
• Conditions: Exotropia Intermittent
• Intervention / Treatment: Device: Prism Glasses; Device: Non-Prism Glasses

• Study Type: Interventional
• Enrollment (Actual): 61
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Alabama
    • Birmingham, Alabama, United States, 35294
      • UAB Pediatric Eye Care; Birmingham Health Care
  • Arizona
    • Glendale, Arizona, United States, 85308
      • Midwestern University Eye Institute
  • Arkansas
    • Little Rock, Arkansas, United States, 72202
      • Arkansas Childrens
  • California
    • Fullerton, California, United States, 92831-1699
      • Southern California College of Optometry
    • Pomona, California, United States, 91766
      • Western University College of Optometry
  • Florida
    • Fort Lauderdale, Florida, United States, 33382
      • Nova Southeastern University College of Optometry, The Eye Institute
  • Illinois
    • Chicago, Illinois, United States, 60611
      • Ann & Robert H. Lurie Children's Hospital of Chicago
    • Chicago, Illinois, United States, 60616
      • Illinois College of Optometry
    • Hyde Park, Illinois, United States, 60637
      • University of Chicago
  • Indiana
    • Bloomington, Indiana, United States, 47405
      • Indiana School of Optometry
    • Indianapolis, Indiana, United States, 47405
      • Indiana University School of Optometry
  • Iowa
    • West Des Moines, Iowa, United States, 50266
      • Wolfe Eye Clinic
  • Kentucky
    • Lexington, Kentucky, United States, 40536
      • University of Kentucky Department of Neurology
  • Maryland
    • Baltimore, Maryland, United States, 21287-9028
      • Wilmer Eye Institute
  • Massachusetts
    • Boston, Massachusetts, United States, 02118
      • Boston Medical Center
    • Boston, Massachusetts, United States, 02453
      • Boston Children's Hospital Waltham
  • Michigan
    • Grand Rapids, Michigan, United States, 49546
      • Pediatric Ophthalmology, P.C.
  • Nebraska
    • Omaha, Nebraska, United States, 68114
      • University of Nebraska Medical Center
  • Ohio
    • Cincinnati, Ohio, United States, 45229
      • Cincinnati Children's Hospital
    • Columbus, Ohio, United States, 43210-1280
      • Ohio State University College of Optometry
  • Oregon
    • Portland, Oregon, United States, 97239
      • OHSU Casey Eye Institute
  • Pennsylvania
    • Erie, Pennsylvania, United States, 16501
      • Pediatric Ophthalmology of Erie
    • Philadelphia, Pennsylvania, United States, 19141
      • Salus University/Pennsylvania College of Optometry
  • Tennessee
    • Nashville, Tennessee, United States, 37232
      • Vanderbilt University Medical Center
  • Texas
    • Houston, Texas, United States, 77030
      • Texas Children's Hospital - Dept. Of Ophthalmology
    • The Woodlands, Texas, United States, 77381
      • Houston Eye Associates
  • Virginia
    • Norfolk, Virginia, United States, 23502
      • Virginia Pediatric Eye Center
  • Wisconsin
    • La Crosse, Wisconsin, United States, 54601
      • Gundersen Health System

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 1 year to 11 years (Child)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Intermittent Exotropia meeting all of the following criteria:

• Age 3 to 13 years
• Mean distance control score of ≥2.00 points with at least 1 measure of 3, 4, or 5 points (i.e, spontaneous tropia) from the 3 assessments during the exam
• A near control score ≤4 on at least 1 of 3 assessments (cannot have score of 5, 5, 5)
• Distance exodeviation between 16 Prism Diopters (Δ) and 35 Δ (inclusive) by PACT
• Near exodeviation between 10 Δ and 35 Δ (inclusive) by PACT
• Near deviation does not exceed distance deviation by more than 10 Δ by PACT (i.e., convergence insufficiency-type IXT excluded)
• Refractive error between -6.00 Diopters (D) spherical equivalent (SE) and +2.50 D SE (inclusive) (based on a cycloplegic refraction performed within 7 months but prior to the day of enrollment)

• Refractive correction (must be worn for at least 1 week if refractive error meets any of the following (based on a cycloplegic refraction performed within 7 months but prior to the day of enrollment):

  • SE anisometropia ≥1.00 D
  • Astigmatism ≥1.00 D in either eye
  • SE myopia ≥-0.50 D in either eye

• If spectacles have been prescribed and are worn, they must meet the following pre- enrollment criteria:

  • SE anisometropia corrected to within 1.00 D of full SE anisometropic difference
  • Astigmatism corrected to within 1.00 D of full magnitude; axis within 10 degrees if astigmatism ≤1.00 D and axis within 5 degrees if astigmatism >1.00 D

Exclusion Criteria:

• Dissociated vertical deviation (DVD)
• Vertical deviation >3 Δ in primary gaze at distance or near
• Patterns (such as an "A" or "V" pattern) with a downgaze measurement of >10 Δ difference from straight ahead by PACT, measured per investigator's routine method
• Treatment for IXT or amblyopia (other than refractive correction) within the past 4 weeks, including vision therapy, orthoptics, patching, atropine, or other penalization
• Substantial overminus spectacles (spectacles overminused by more than 1.00 D SE than the most recent cycloplegic refraction and also results in minus SE power in the spectacles; underplussing is allowed) within the past 4 weeks
• Prior strabismus, intraocular, or refractive surgery (including BOTOX injection)
• Previous use of prism spectacles

Additional Eligibility Criteria for Randomization Based on Prism Adaptation Testing

• Exodeviation by PACT while wearing "trial" relieving prism for 30 minutes is smaller at distance or near than measured during initial testing (e.g. not fully adapting to prism at both distances)
• No new esotropia on cover test at near while wearing "trial" relieving prism for 30 minutes, compared with enrollment measurement taken without prism
• No esodeviation >6 Δ on PACT at near while wearing "trial" relieving prism for 30 minutes

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Prism Group; Spectacles with refractive correction and base-in relieving prism (40% of the greater of the exodeviation by prism and alternate cover test (PACT) at distance or near) equally divided between the 2 lenses will be prescribed to the participant	Device: Prism Glasses; Spectacles with refractive correction and base-in relieving prism (40% of the greater of the exodeviation by PACT at distance or near) equally divided between the 2 lenses
Placebo Comparator: Non-Prism Group; Spectacles with refractive correction (or plano spectacles if no significant refractive error) and no prism will be prescribed to the participant	Device: Non-Prism Glasses; Spectacles with refractive correction (or plano spectacles if no significant refractive error) and no prism

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Exotropia Control Score at Distance, Continuous Score	The primary analysis will be an intent-to-treat comparison of mean 8-week control of the distance exodeviation (average of 3 measurements) between treatment groups using an analysis of covariance (ANCOVA) model, which adjusts for baseline distance control. Distance control scores range from 0 to 5 with higher scores indicating a worse outcome.	8 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Exotropia Control Score at Distance, % With Treatment Response	The secondary analysis will calculate the percentage of participants with a "treatment response," defined as ≥1 point improvement in control of their distance exodeviation (average of 3 measurements) between baseline and the 8-week outcome exam.	8 weeks
Exotropia Control Score at Distance and Near, % With No Spontaneous Tropia	The proportion of participants with no spontaneous tropia at 8 weeks will be compared between treatment groups using a two-sided Barnard's test with alpha of 0.05, with calculation of a two-sided 95% confidence interval on the difference in proportions. No spontaneous tropia at the 8-week primary outcome exam is defined as a score of ≤2 (0, 1, or 2) on all three assessments of control at distance and at near.	8 Weeks
Exotropia Control Score at Distance, Continuous Change Between Baseline and 8 Weeks	Control of the exodeviation was measured at distance using the IXT Office Control Score, (Mohney, 2006) which ranges from 0 (phoria) to 5 (constant exotropia). Control levels 3-5 were assigned based on the duration of manifest exotropia during a 30-second period before any dissociation. If no exotropia was observed, control levels 0-2 were assigned based on the longest time to reestablishing fusion after 3 consecutive 10-second periods of dissociation. Control was measured at the beginning, middle, and end (3 tests) of a 20- to 40-minute office examination, and the mean was used. The change in distance control from baseline to 8 weeks will be calculated. A negative value indicates improvement.	8 Weeks
Exotropia Control Score at Near, Continuous Score	Near control will be evaluated similarly to the primary outcome and outcome measures 2-4. Near control scores range from 0 to 5 with higher scores indicating a worse outcome.	8 Weeks
Exodeviation by PACT at Distance, Continuous	The measure of ocular alignment at distance by PACT will be summarized at 8 weeks for each treatment group. A higher deviation is worse.	8 Weeks
Exodeviation by PACT at Near, Continuous	The measure of ocular alignment at near by PACT will be summarized at 8 weeks for each treatment group. A higher deviation is worse.	8 Weeks
Randot Preschool Stereoacuity at Near, Continuous	Randot® Preschool Stereoacuity test (Stereo Optical Co., Inc., Chicago, IL). For analysis, stereoacuity was converted from seconds of arc scores to log arcsec values (in parentheses) as follows: 40 (1.60), 60 (1.78), 100 (2.00), 200 (2.30), 400 (2.60), 800 (2.90); participants with no detectable (nil) stereoacuity were assigned the value of 1600 (3.20). The measure of Randot Preschool Stereoacuity at near will be summarized at 8 weeks for each treatment group. A lower score is better.	8 Weeks
Compliance of Spectacle Wear	Parents will be asked to complete a compliance calendar by recording the percentage of time their child has worn the study-prescribed spectacle correction each day. Proportion of time worn each day will be described as excellent (76% to 100%), good (51% to 75%), fair (26% to 50%), poor (1 to 25%), or none (0%). Based on review of the calendars and discussion with parents at the 8-week outcome exam, the investigator will record the total proportion of time worn as excellent (76% to 100%), good (51% to 75%), fair (26% to 50%), poor (1 to 25%), or none (0%: did not fill prescription or never picked up spectacles). The distribution of compliance will be assessed for each treatment group at the outcome exam.	8 weeks
Child Assessment of Symptoms - Do Your Eyes Hurt?	Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Child Assessment of Symptoms - Do Your Eyes Feel Funny?	Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Child Assessment of Symptoms - Do You Have Double Vision?	Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Child Assessment of Symptoms - Is it Hard for You to Stare at Things?	Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Child Assessment of Symptoms - Do You Have Problems With Your Eyes in the Sun?	Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Child Assessment of Symptoms - Do Your Eyes go in and Out?	Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Child Assessment of Symptoms - Is it Hard to Focus Your Eyes?	Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Parent Assessment of Symptoms and Spectacle Wear - Has Your Child Had Headaches?	Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent. Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Parent Assessment of Symptoms and Spectacle Wear - Has Your Child Had Eyestrain?	Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent. Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Parent Assessment of Symptoms and Spectacle Wear - Has Your Child Avoided Reading or Doing Things up Close?	Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent. Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Parent Assessment of Symptoms and Spectacle Wear - Has Your Child Reported Blurry Vision?	Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent. Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Parent Assessment of Symptoms and Spectacle Wear - Has Your Child Looked Over His or Her Spectacles?	Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent. Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Parent Assessment of Symptoms and Spectacle Wear - Has Your Child Taken His/Her Spectacles Off When he/She Should be Wearing Them?	Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent. Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks
Parent Assessment of Symptoms and Spectacle Wear - Has Your Child Complained That the Spectacles Hurt His/Her Ears and/or Nose?	Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent. Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.	8 Weeks

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Distance Visual Acuity (Snellen Equivalent)	Distance visual acuity will be assessed at the 8-week outcome exam. Any optotype method can be used for testing. The distribution of distance visual acuity Snellen Equivalents will be tabulated for each treatment group. A lower Snellen Equivalent is best.	8 Weeks
Fusional Convergence - Continuous Break Point	As an exploratory analysis, the distribution of fusional convergence amplitude (break point, blur point, and recovery) at 8 weeks will be summarized for each treatment group. Fusional amplitudes are a measure of how well a participant can converge their eyes using fusional vergence. It is measured by increasing base-out prism to the point that the participant is no longer able to control the deviation. The total amount of fusion is the magnitude of the base-out prism the participant was able to overcome plus the magnitude of the deviation. A higher number of prism diopters for break point is better than a lower number. A lower number for recovery point is better than a higher number.	8 Weeks
Suppression	The suppression assessment is a standardized method of assessing the depth of suppression experienced while the participant is tropic (NOT aligned). Scoring is reported on an ordinal scale from 0 (no suppression) to 3 (dense suppression). "Missing" refers to cases in which participants were unable to understand the test and/or gave unreliable responses. As an exploratory analysis, the distribution of suppression level (none, mild, moderate, severe, missing) will be tabulated after 8 weeks by treatment group.	8 Weeks
Fusional Convergence - Continuous Recovery Point	As an exploratory analysis, the distribution of fusional convergence amplitude (break point, blur point, and recovery) at 8 weeks will be summarized for each treatment group. Fusional amplitudes are a measure of how well a participant can converge their eyes using fusional vergence. It is measured by increasing base-out prism to the point that the participant is no longer able to control the deviation. The total amount of fusion is the magnitude of the base-out prism the participant was able to overcome plus the magnitude of the deviation. A higher number of prism diopters for break point is better than a lower number. A lower number for recovery is better than a higher number.	8 Weeks

Collaborators and Investigators

• Sponsor: Jaeb Center for Health Research
• Collaborators: National Eye Institute (NEI); Pediatric Eye Disease Investigator Group
• Investigators: Study Chair: David G Morrison, MD, Vanderbilt University Medical Center; Study Chair: Allison I Summers, OD, MCR, Oregon Health and Science University

Publications and helpful links

General Publications

• Summers AI, Morrison DG, Chandler DL, Henderson RJ, Chen AM, Leske DA, Walker KR, Li Z, Melia BM, Bitner DP, Kurup SP, Allen M, Phillips PH, Nash DL, Grigorian AP, Kraus CL, Miller AM, Titelbaum JR, Kraker RT, Holmes JM, Cotter SA; Pediatric Eye Disease Investigator Group. A Pilot Randomized Clinical Trial of Base-in Relieving Prism Spectacle Treatment of Intermittent Exotropia. Optom Vis Sci. 2023 Jul 1;100(7):432-443. doi: 10.1097/OPX.0000000000002039. Epub 2023 Jul 1.
• Hatt SR, Leske DA, Holmes JM, Henderson RJ, Chandler DL, Morrison DG, Summers AI, Cotter SA. Testing depth of suppression in childhood intermittent exotropia. J AAPOS. 2022 Feb;26(1):36-38.e1. doi: 10.1016/j.jaapos.2021.08.303. Epub 2021 Nov 16.

Helpful Links

• PEDIG Public Website

Study record dates

Study Major Dates

• Study Start (Actual): September 1, 2019
• Primary Completion (Actual): July 30, 2020
• Study Completion (Actual): July 30, 2020

Study Registration Dates

• First Submitted: June 24, 2019
• First Submitted That Met QC Criteria: June 25, 2019
• First Posted (Actual): June 26, 2019

Study Record Updates

• Last Update Posted (Actual): October 4, 2023
• Last Update Submitted That Met QC Criteria: September 27, 2023
• Last Verified: September 1, 2023

More Information

Terms related to this study

• Keywords: Prism
• Additional Relevant MeSH Terms: Nervous System Diseases; Eye Diseases; Cranial Nerve Diseases; Ocular Motility Disorders; Strabismus; Exotropia; Physiological Effects of Drugs; Adrenergic Agents; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Autonomic Agents; Peripheral Nervous System Agents; Neurotransmitter Uptake Inhibitors; Membrane Transport Modulators; Dopamine Agents; Dopamine Uptake Inhibitors; Central Nervous System Stimulants; Sympathomimetics; Adrenergic Uptake Inhibitors; Methamphetamine
• Other Study ID Numbers: IXT6; 2UG1EY011751 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: In accordance with the NIH data sharing policy, a de-identified database is placed in the public domain on the Pediatric Eye Disease Investigator Group (PEDIG) public website after the completion of each protocol and publication of the primary manuscript.
• IPD Sharing Time Frame: Data will be made available after publication.
• IPD Sharing Access Criteria: Users accessing the data must enter an email address.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No