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.
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
Subjects with strabismus
Subjects with visual acuity of less than 20/20; or anisometropia
Any individual between the ages of 18 and 35, inclusive, with no organic ophthalmological disorders or oculomotor disorders.
Other
Prospective
Fusional Vergence assessment
Other interventionMeasurement 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.
Ocular dominance evaluation
Other interventionAssessment 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
Complete Orthoptic
Other interventionConducting 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
Amplitude of fusional vergence
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.
Laterality ocular dominance
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.
Lateralization quotient value (LQ)
Determination of the lateralization quotient value by the mean of previous responses of the ocular dominance tests.
Assessment of the degree of agreement among the various tests for ocular dominance
Compilation of responses to ocular dominance tests (sensorial and motor dominant eye, target eye and preferred eye) and lateralization quotient.
Agreeement between the bilateral prismatic test (new test for oculomotor dominance laterality determination and standard ocular dominance tests
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.
Assessment of the difference in fusional vergence measurements between the right and left eyes and the laterality quotient
Assessment of the difference in fusional vergence measurements between the right and left eyes and the laterality quotient.
Correlation between inter-pupillary distance measurements and differences in fusion amplitude measurements between the right and left eyes
Measurements of interpupillary distance and overall fusion ability, for distance vision and near vision.
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Assistance Publique - Hôpitaux de Paris
Lead sponsor
URC-CIC Paris Descartes Necker Cochin
Collaborator
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