Prism Adaptation in Symptomatic Esophoria - Effect of Shorter Time Intervals and Surgical Outcomes Based on Prism Adaptation

This study is a prospective randomized study aiming to investigate the effect of prism adaptation before surgery for symptomatic esophoria on the number of reoperations, the occurrence of over- and under-correction after the first surgery, and symptom resolution. Additionally, we aim to define the optimal duration of prism adaptation.

Study Overview

• Status: Recruiting
• Conditions: Esophoria
• Intervention / Treatment: Procedure: Prism adaptation test; Procedure: other

Detailed Description

SUBSTUDY 1 The Optimal Duration of Prism Adaptation in Symptomatic Esophoria Study Design: Prospective, randomized controlled study Patient Group: 100 participants with symptomatic esophoria, randomized into two groups of 50 participants each to undergo either one hour or four hours of prism adaptation.

The purpose of this study is to determine the optimal duration of prism adaptation.

The hypothesis is that the measured deviation angle is expected to increase after one hour of prism adaptation compared to before prism adaptation. Furthermore, it is expected that the measured deviation angle will not differ significantly between the two randomization groups. The primary endpoint is the measured deviation angle at the conclusion of prism adaptation.

The results are highly relevant for accurate surgical dosing (and thus postoperative symptoms and reoperation rates), efficient use of hospital resources, and reduced patient waiting times in the outpatient clinic.

SUBSTUDY 2 Strabismus Surgery for Symptomatic Esophoria Based on Prism Adaptation Study Design: Prospective, randomized controlled study Patient Group: 100 participants with symptomatic esophoria, using the same patients and randomization groups as in Substudy 1.

The purpose of this study is to investigate the effectiveness of strabismus surgery for symptomatic esophoria based on prism adaptation. Patients randomized in Substudy 2 to either one or four hours of prism adaptation will undergo surgery based on the full prism-adapted angle.

The hypothesis for this substudy is that surgical dosing based on one hour of prism adaptation will be equivalent to dosing based on four hours of prism adaptation. The primary endpoint will be the reoperation rate. Secondary endpoints will include comparisons of preoperative surgical planning metrics (target deviation and number of eye muscles operated), symptom resolution after the first surgery, and prism measurements (including rates of over- and undercorrections).

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Mikael Hofsli, M.D; Phone Number: 004538634381; Email: mikael.hofsli@regionh.dk

Study Locations

• Denmark
  • Copenhagen, Denmark, 2600
    • Recruiting
    • Rigshospitalet
    • Contact: Mikael Hofsli, MD; Phone Number: +4538634755; Email: mikael.hofsli@regionh.dk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Patients with symptomatic esophoria who meet one or more of the following criteria:

• Double vision
• Asthenopia (eye strain)
• Headaches related to esophoria
• Worsening of symptoms during fatigue, sleep deprivation, reading, illness, or alcohol consumption.

Exclusion Criteria:

• Age between 18 and 65 years at date of inclusion.
• Accommodative esotropia or esophoria
• Myopia exceeding 10 diopters in the most myopic meridian
• Treatment with botulinum toxin in an eye muscle within four months prior to inclusion
• Inability to undergo reliable orthoptic measurements or prism adaptation
• Previous strabismus surgery
• Pregnancy or breastfeeding within 12 months prior to inclusion
• Myogenic disorders (including Myasthenia Gravis)
• Restrictive strabismus (including previous eye muscle trauma or Graves' orbitopathy)
• Eye muscle paresis
• Maximum prism-adapted deviation angle >40 prism diopters (PD) in any gaze direction for distance
• Maximum prism-adapted deviation angle with ≥20 PD difference between near and distance measurements

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: 1 hour prism adaptation; Patients who receive one hour of prism adaptation.	Procedure: Prism adaptation test; Prism Adapation test for 1 hour in one group, and 4 hours in second group; Procedure: other; Surgery based on prism adaptation test of 1 hour in one group and 4 hours in second group; Other Names: Surgery based on prism adaptation test
Active Comparator: 4 hours of prism adaptation; Patients who receive four hour of prism adaptation.	Procedure: Prism adaptation test; Prism Adapation test for 1 hour in one group, and 4 hours in second group; Procedure: other; Surgery based on prism adaptation test of 1 hour in one group and 4 hours in second group; Other Names: Surgery based on prism adaptation test

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Reoperation rate	Number of patients in need of reoperation after initial surgery for symptomatic esophoria	Up to 5 years
Measured deviation angle at the conclusion of prism adaptation.	Measured deviation angle in prism diopters at the conclusion of prism adaptation.	Up to 5 years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Motor success	Motor success: 10 prism diopters of esophoria to 5 prism diopters of exophoria measured with prism alternating cover test. Motor failure: Manifest strabismus measured with prism alternating cover test	1 year from date of surgery
Sensory success	Sensory success: Postoperative unchanged or improvement in stereopsis measured in seconds of arc with the same method (LANG I/II or TNO) in compared to baseline.	1 year from date of surgery
Symptomatic success	Symptomatic success: Single vision (defined as the absence of double vision in daily life) and/or absence of asthenopia (defined as eye strain that is significant in daily life)	1 year from date of surgery

Collaborators and Investigators

• Sponsor: Rigshospitalet, Denmark

Study record dates

Study Major Dates

• Study Start (Actual): May 19, 2025
• Primary Completion (Estimated): January 1, 2028
• Study Completion (Estimated): January 1, 2030

Study Registration Dates

• First Submitted: December 4, 2024
• First Submitted That Met QC Criteria: December 9, 2024
• First Posted (Actual): December 11, 2024

Study Record Updates

• Last Update Posted (Actual): July 22, 2025
• Last Update Submitted That Met QC Criteria: July 21, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Keywords: strabismus surgery; prism adaptation; Esophoria
• Additional Relevant MeSH Terms: Nervous System Diseases; Eye Diseases; Cranial Nerve Diseases; Ocular Motility Disorders; Strabismus; Esotropia
• Other Study ID Numbers: H-24017032

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No