Saccadic Reaction Times and Computational Modelling Reveal Heterogeneous Binocular Summation in Glaucomatous Visual...

Area of Science:

• Ophthalmology
• Neuroscience
• Visual Science

Background:

• Binocular summation enhances visual performance by integrating information from both eyes.
• Glaucoma, a condition causing interocular asymmetries, may disrupt binocular summation.
• Reaction times (RTs) are key indicators of visual processing efficiency but are understudied in binocular glaucoma.

Purpose of the Study:

• To quantify monocular and binocular saccadic reaction times (RTs) in glaucoma patients and healthy controls using eye-movement perimetry (EMP).
• To compare binocular summation between healthy and glaucoma participants.
• To evaluate the correspondence of observed binocular summation with computational models.

Main Methods:

• Saccadic RTs were measured monocularly and binocularly at multiple visual field locations under varying contrast conditions.
• Participants included seven healthy individuals and eight with glaucoma of varying severity.
• Data analysis involved reciprobit plots, estimation statistics, and linear mixed-effects modeling, comparing results with statistical facilitation and neural integration models.

Main Results:

• Healthy participants showed a consistent binocular advantage (~20 ms faster RTs), aligning with statistical facilitation predictions.
• Glaucoma participants exhibited heterogeneous binocular summation, with some showing preserved summation and others slower binocular RTs than the fastest monocular RT.
• Computational models suggested most glaucoma cases fit statistical facilitation, but some indicated inhibitory interactions or monocular dominance.

Conclusions:

• Binocular RTs serve as a sensitive measure of visual processing and highlight diverse binocular summation mechanisms in glaucoma.
• Eye-movement perimetry under binocular conditions is a promising tool for assessing functional visual impairment in glaucoma.
• Understanding binocular summation deficits is crucial for managing visual impairment in glaucoma.