Assessing Binocular Central Visual Field and Binocular Eye Movements in a Dichoptic Viewing Condition

Summary

Presented here is a protocol for assessing binocular eye movements and gaze-controlled central visual field screening in participants with central vision loss.

Abstract

Macular degeneration typically results in heterogeneous binocular central visual defects. Currently available approaches to assess central visual field, like the microperimetry, can test only one eye at a time. Therefore, they cannot explain how the defects in each eye affect the binocular interaction and real-world function. Dichoptic stimulus presentation with a gaze-controlled system could provide a reliable measure of monocular/binocular visual fields. However, dichoptic stimulus presentation and simultaneous eye-tracking are challenging because optical devices of instruments that present stimulus dichoptically (e.g., haploscope) always interfere with eye-trackers (e.g., infrared video-based eye-trackers). Therefore, the goals were 1) to develop a method for dichoptic stimulus presentation with simultaneous eye-tracking, using 3D-shutter glasses and 3D-ready monitors, that is not affected by interference and 2) to use this method to develop a protocol for assessing central visual field in subjects with central vision loss. The results showed that this setup provides a practical solution for reliably measuring eye-movements in dichoptic viewing condition. In addition, it was also demonstrated that this method can assess gaze-controlled binocular central visual field in subjects with central vision loss.

Introduction

Macular degeneration is generally a bilateral condition affecting central vision and the pattern of visual loss can be heterogeneous. The central visual loss could be either symmetrical or asymmetrical between two eyes¹. Currently, there are several techniques available to assess the central visual field in macular degeneration. The Amsler grid chart contains a grid pattern that can be used to manually screen central visual field. Automated perimeters (e.g., Humphrey visual field analyzer) present light flashes of varying brightness and sizes in a standardized ganzfeld bowl to probe the visual field. Gaze-contingent microperimetry presents visu....

Protocol

All the procedures and protocol described below were reviewed and approved by the institutional review board of Wichita State University, Wichita, Kansas. Informed consent was obtained from all the participants.

1. Participant selection

1. Recruited participants with normal vision (n=5, 4 females, mean ± SE: 39.8 ± 2.6 years), and with central vision loss (n=15, 11 females, 78.3 ± 2.3 years) due to macular degeneration (age-related/juvenile). Note that grossly different ages of the two groups was secondary to demographics of the subjects with central vision loss (age-related macular degeneration affects older subject....

Results

The representative binocular eye-movement traces of one observer with normal binocular vision during two different viewing conditions is shown (Figure 4). Continuous tracking of eye movements was possible when both eyes viewed the stimulus (Figure 4A), and when the left eye viewed the stimulus with the right eye under an active shutter (Figure 4B). As evident from these traces, the proposed method does not impact the quality of eye-.......

Discussion

The proposed method of measuring eye movements in dichoptic viewing condition has many potential applications. Assessing binocular visual fields in participants with central vision loss that is demonstrated here is one such application. We used this method to assess binocular visual field in fifteen participants with central vision loss to study how binocular viewing influences the heterogeneous central visual field loss.

The most important step in the protocol is positioning (distance from ey.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3D monitor	Benq	NA	Approximate Cost (in USD): 500 https://zowie.benq.com/en/product/monitor/xl/xl2720.html
3D shutter glass	NVIDIA	NA	Approximate Cost (in USD): 300 https://www.nvidia.com/object/product-geforce-3d-vision2-wireless-glasses-kit-us.html
Chin/forehead rest	UHCO	NA	Approximate Cost (in USD): 750 https://www.opt.uh.edu/research-at-uhco/uhcotech/headspot/
Eyetracker	SR Research	NA	Approximate Cost (in USD): 27,000 https://www.sr-research.com/eyelink-1000-plus/
IR reflective patch	Tactical	NA	Approximate Cost (in USD): 10 https://www.empiretactical.org/infrared-reflective-patches/tactical-infrared-ir-square-patch-with-velcro-hook-fastener-1-inch-x-1-inch
MATLAB Software	Mathworks	NA	Approximate Cost (in USD): 2150 https://www.mathworks.com/pricing-licensing.html
Numerical Keypad	Amazon	CP001878 (model), B01E8TTWZ2 (ASIN)	Approximate Cost (in USD): 15 https://www.amazon.com/Numeric-Jelly-Comb-Portable-Computer/dp/B01E8TTWZ2
Psychtoolbox - Add on	Freeware	NA	Approximate Cost (in USD): FREE http://psychtoolbox.org/download.html
Tripod (Dekstop)	Manfrotto	MTPIXI-B (model), B00D76RNLS (ASIN)	Approximate Cost (in USD): 30 https://www.amazon.com/dp/B00D76RNLS