A Comparative Study of Fusional Vergence According to Ocular Dominance in Healthy Subjects (ECAFOSS)

July 6, 2026 updated by: Assistance Publique - Hôpitaux de Paris

In orthoptics, fusional vergence (FV) measurement is one of the key tests used to assess fusion ability. These amplitudes are generally reduced in individuals with convergence insufficiency. Fusional vergence are quantified by placing a prism bar randomly in front of one eye-first for distance vision and then for near vision. Rehabilitation exercises using the prism bar are also performed in the same manner.

Depending on orthoptic practice, the prism bar is placed in front of the left eye or the right eye, in a dogmatic manner, or in front of the right eye, in a conventional manner, without any study providing any justification. However, some practitioners report interocular differences when measuring fusion amplitudes depending on which eye is prismed, while others do not.

The hypothesis put forward is that, in individuals with an interocular difference in fusional vergence, ocular dominance (sensory and motor) could be the cause of this measurement discrepancy.

The objective is therefore to compare the difference in fusional vergence depending on whether the dominant or non-dominant eye is tested, using a randomized order of eyes and tests.

If this hypothesis is confirmed (greater fusional vergence when tested on the dominant eye), this would: (1) enhance our understanding of fusion mechanisms, (2) provide more targeted insights for the assessment, quantification, and rehabilitation of fusional vergence to improve the effectiveness of orthoptic intervention.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

In orthoptics, fusional vergence (FV) measurement is one of the key tests used to assess fusion ability. These amplitudes are generally reduced in individuals with convergence insufficiency. Fusional vergence are quantified by placing a prism bar randomly in front of one eye-first for distance vision and then for near vision. Rehabilitation exercises using the prism bar are also performed in the same manner.

Depending on orthoptic practice, the prism bar is placed in front of the left eye or the right eye, in a dogmatic manner, or in front of the right eye, in a conventional manner, without any study providing any justification. However, some practitioners report interocular differences when measuring fusion amplitudes depending on which eye is prismed, while others do not.

The hypothesis put forward is that, in individuals with an interocular difference in fusional vergence, ocular dominance (sensory and motor) could be the cause of this measurement discrepancy.

The objective is therefore to compare the difference in fusional vergence depending on whether the dominant or non-dominant eye is tested, using a randomized order of eyes and tests.

If this hypothesis is confirmed (greater fusional vergence when tested on the dominant eye), this would: (1) enhance our understanding of fusion mechanisms, (2) provide more targeted insights for the assessment, quantification, and rehabilitation of fusional vergence to improve the effectiveness of orthoptic intervention.

The study consists of one-hour eye examinations of healthy individuals with no visual or oculomotor disorders.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
60

Contacts and Locations

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

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

Study Locations

  • France
      • Paris, France, 75015
        • Hôpital Necker-Enfants Malades
        • Contact:

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Any individual between the ages of 18 and 35, inclusive, with no organic ophthalmological disorders or oculomotor disorders.

Description

Inclusion Criteria:

  • Adults between the ages of 18 and 35 with no known eye conditions, with or without ametropia. If ametropia is present: it must be corrected
  • Subjects with no history of eye surgery, including refractive surgery
  • Subjects who have been informed about the study and have freely and knowingly consented to participate in the study and to the collection of data

Exclusion Criteria:

  • Subjects with strabismus
  • Subjects with visual acuity of less than 20/20; or anisometropia

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

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Healthy individual
Individuals with no visual or oculomotor disorders.
Other: Fusional Vergence assessment
Measurement of sensorimotor fusional vergence in the right and left eyes, in divergence and convergence, first for distance vision and then for near vision. A random draw will determine which eye is tested first for distance vision, followed by a second draw for near vision, in order to minimize training bias. Prior to this, a stereoscopic acuity test will be performed to confirm the presence of binocular vision.
Other Names:
  • Measurements of sensorimotor fusion
Other: Ocular dominance evaluation

Assessment of ocular dominance for:

  • The dominant eye using the monocular blurriness test and the red-glass test
  • The leading eye using the Mawas plate Punctum Proximum convergence test and the bilateral prismatic test for oculomotor dominance
  • The preferred eye using the spontaneous ocular method
  • The target eye using the Hole-in-Card method: hole-in-card test
Other Names:
  • Assessment of ocular dominance
Other: Complete Orthoptic

Conducting an orthoptic evaluation to verify that patients meet the study's inclusion criteria:

  • assessment of visual acuity and refraction
  • assessment of stereoscopic vision
  • cover-test to screen potential abnormal phorias
  • measurement of interpupillary distance
Other Names:
  • Orthoptic evaluation

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Amplitude of fusional vergence
Time Frame: Day 0
Values of horizontal fusional vergence measured using a horizontal Berens prism bar in divergence and convergence, for distance and near vision, in the right eye and the left eye and reported in prism diopters.
Day 0
Laterality ocular dominance
Time Frame: Day 0

Assessment of ocular dominance for:

  • The dominant eye using the monocular blur test and the red-glass test
  • The leading eye using the Punctum Proximum of Convergence (PPC) test with the Mawas plate and bilateral prism test for oculomotor dominance
  • The preferred eye using the spontaneous ocular method
  • The target eye using the Hole-in-Card method: hole-in-card test All tests classify the ocular dominance into 3 categories : Left, Right, None.
Day 0
Lateralization quotient value (LQ)
Time Frame: Day 0
Determination of the lateralization quotient value by the mean of previous responses of the ocular dominance tests.
Day 0

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Assessment of the degree of agreement among the various tests for ocular dominance
Time Frame: Day 0
Compilation of responses to ocular dominance tests (sensorial and motor dominant eye, target eye and preferred eye) and lateralization quotient.
Day 0
Agreeement between the bilateral prismatic test (new test for oculomotor dominance laterality determination and standard ocular dominance tests
Time Frame: Day 0
Evaluation of a new test (bilateral prismatic test for oculomotor dominance) and comparison to usually ocular dominance test. All tests classify the ocular dominance into 3 categories : Left, Right, None. This part tends to evaluation the efficacity and the utility of a new test for ocular dominance.
Day 0
Assessment of the difference in fusional vergence measurements between the right and left eyes and the laterality quotient
Time Frame: Day 0
Assessment of the difference in fusional vergence measurements between the right and left eyes and the laterality quotient.
Day 0
Correlation between inter-pupillary distance measurements and differences in fusion amplitude measurements between the right and left eyes
Time Frame: Day 0
Measurements of interpupillary distance and overall fusion ability, for distance vision and near vision.
Day 0

Collaborators and Investigators

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

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Assistance Publique - Hôpitaux de Paris

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
URC-CIC Paris Descartes Necker Cochin

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Maxence Rateaux, PhD, Assistance Publique - Hôpitaux de Paris
  • Study Director: Dominique MD, PhD BREMOND-GIGNAC, Assistance Publique - Hôpitaux de Paris

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

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Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
September 1, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
July 1, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 1, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
June 22, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 6, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
July 13, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
July 13, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 6, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
June 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • APHP251987
  • 2025-A02953-46 (Other Identifier: ID RCB number)

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

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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