Study of the Angle Lambda and Ocular Dominance (EPOLAF)

Study of the Correlations Between the Ocular Dominance Depth, the Angle Lambda and the Fixation Disparity in Healthy Individuals

Anatomical ophthalmological connections and their dynamics are still debated in the scientific community. However, their considering is essential in many surgeries (strabismus, cataract, refractive...) or in clinical practice.

The correlation between these biometric values would make it possible to refine the knowledge related to these landmarks and thus offer better ophthalmological management by integrating these variables into the clinical examination.

The aim of the study is to analyze the correlation between the angle lambda and the ocular dominance depth in healthy individuals without ophthalmologic disorder.

Then, seconds goals were defined as the study of the relation between the value of the angle lambda and the fixation disparity quantified with the Rousseau test.

Relation between ocular dominance measured with the Guillon's test and the Hole-in-car test will also studied.

Study Overview

• Status: Completed
• Conditions: No Eye Disorder
• Intervention / Treatment: Other: Eye examination

Detailed Description

The angle lambda corresponds to the angle formed by the pupillary axis (line passing through the center of the pupil and perpendicular to the cornea) and the line of sight (broken line between the fixation point and the fovea and passing through the center of the pupil entrance). The angle kappa corresponds to the angle between the visual axis (line between the point of fixation and the fovea: area of the retina allowing precise vision) and the pupillary axis.

The angle lambda and the angle kappa are very close, which is why the lambda angle is often equated with the kappa angle, both in practice and in the literature.

The literature reports a non-null angle kappa ranged between 1.91° ± 0.14° and 5.73° ± 0.10° in the general population. Also, studies have reported a significantly greater angle on the left eye compared to the right eye. Moreover - because of the interpupillary difference - each eye perceives the same image from a different angle, resulting in a fixation disparity, defined as the angle of the residual deviation of the visual axes when the subject fixes and binocularly merges an image. In some cases, too high a value of the disparity can lead to a fixation disorder requiring orthoptic treatment.

Anatomical ophthalmological connections and their dynamics are still debated in the scientific community. However, their considering is essential in many surgeries (strabismus, cataract, refractive...) or in clinical practice.

The correlation between these biometric values would make it possible to refine the knowledge related to these landmarks and thus offer better ophthalmological management by integrating these variables into the clinical examination.

The aim of the study is to analyze the correlation between the angle lambda and the ocular dominance depth and the fixation disparity in a healthy population without ophthalmologic disorder.

Then, seconds goals were defined as the study of the relation between the value of the angle lambda and the fixation disparity quantified with the Rousseau test.

Relation between ocular dominance measured with the Guillon's test and the Hole-in-car test will also studied.

• Study Type: Observational
• Enrollment (Actual): 76

Contacts and Locations

Study Locations

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

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Healthy individuals without visual disorders

Description

Inclusion Criteria:

- Informed major subject not opposing to their participation in the study

Exclusion Criteria:

• Subject with strabismus or organic ophthalmologic pathology
• Or presenting a visual acuity lower than 10/10th
• Or with a history of eye surgery

Study Plan

How is the study designed?

Design Details

• Observational Models: Other
• Time Perspectives: Prospective

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Healthy individual; Healthy individual without eye disorder.	Other: Eye examination; orthoptic assessment (visual acuity, refraction, stereopsis test, Cover-test, evaluation of the disparity of fixation and ocular dominance, measurement of the inter-pupillary distance; ocular biometry; corneal topography; monocular photographs in photopic condition

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Value of the angle lambda	Semi-automatic digital method of measurement by eye photograph.	Day 0
Ocular dominance depth	Guillon's and Hole-In-Card tests.	Day 0

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fixation disparity	Rousseau test.	Day 0
Ocular dominance measurements quantified by the Hole-in-the-card method	Ocular dominance.	Day 0
Guillon test	Ocular dominance.	Day 0
Semi-automatic method of measurement by ocular photography	Compare the values of the lambda angle obtained using the semi-automatic method of measurement by ocular photography and the method using corneal topography.	Day 0
Method using corneal topography	Compare the values of the lambda angle obtained using the semi-automatic method of measurement by ocular photography and the method using corneal topography.	Day 0

Collaborators and Investigators

• Sponsor: Assistance Publique - Hôpitaux de Paris
• Collaborators: URC Necker Cochin, France
• Investigators: Principal Investigator: Maxence Rateaux, PhD, Assistance Publique - Hôpitaux de Paris; Study Director: Dominique Bremond-Gignac, MD, PhD, Assistance Publique - Hôpitaux de Paris

Study record dates

Study Major Dates

• Study Start (Actual): November 25, 2022
• Primary Completion (Actual): February 28, 2024
• Study Completion (Actual): February 28, 2024

Study Registration Dates

• First Submitted: November 4, 2022
• First Submitted That Met QC Criteria: November 4, 2022
• First Posted (Actual): November 14, 2022

Study Record Updates

• Last Update Posted (Estimated): September 12, 2025
• Last Update Submitted That Met QC Criteria: September 5, 2025
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Keywords: Angle lambda; Ocular dominance; Fixation disparity; Pupillary axis; Line of sight
• Additional Relevant MeSH Terms: Eye Diseases
• Other Study ID Numbers: APHP221023; 2022-A01045-38 (Other Identifier: IDRCB 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
• product manufactured in and exported from the U.S.: No