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

Summary

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.

Conditions

• No Eye Disorder

Interventions

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

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

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

Sponsors & Collaborators

• URC-CIC Paris Descartes Necker Cochin

  collaborator OTHER

• Assistance Publique - Hôpitaux de Paris

  lead OTHER

Principal Investigators

• Maxence Rateaux, PhD · Assistance Publique - Hôpitaux de Paris

• Dominique MD, PhD BREMOND-GIGNAC · Assistance Publique - Hôpitaux de Paris

Eligibility

Min Age

18 Years

Max Age

35 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2026-08-20

Primary Completion

2027-06-30

Completion

2027-06-30

Countries

• France

Study Locations