Training to Modify Fixational Eye Movements for Optimizing Visual Performance in People With Central Vision Loss

Training to Modify Fixational Eye Movements for Optimizing Visual Performance

People with central vision loss almost all have exaggerated fixational eye movements when compared with people with normal vision (e.g. larger amplitudes of microsaccades and ocular drifts). Central vision loss primarily results from eye diseases or disorders that affect the macular region of the retina, such as age-related macular degeneration (AMD) and Stargardt disease. The clinical wisdom is that exaggerated fixational eye movements are detrimental to vision. This forms the basis of the increasing number of clinical trials that use fixation stability (variability of eye positions during fixation) as an outcome measure to evaluate the effectiveness of interventions on age-related macular degeneration or other retinal diseases, despite the lack of causal evidence supporting or refuting a relationship between fixational eye movements and functional vision. If excessive fixational eye movements are indeed detrimental to vision for people with central vision loss, can we reduce the amount of their fixational eye movements, thus improve their fixation stability? And if so, does that lead to improved functional vision? The goal of this study is to examine the hypothesis that retinal image motion due to abnormal fixational eye movements can be modified through fixation training, with accompanied improvements in functional vision as a result.

Study Overview

• Status: Active, not recruiting
• Conditions: Central Vision Loss From Macular Diseases
• Intervention / Treatment: Behavioral: Fixation training

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • California
    • Berkeley, California, United States, 94720
      • Herbert Wertheim School of Optometry & Vision Science, University of California Berkeley

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

Participants with normal vision:

• age 18 or above
• best corrected visual acuity of at least 20/20 in each eye
• cataracts, if present, must be minimal (grade 1 or below according to the Lens Opacity Classification System)
• normal contrast sensitivity for their ages
• stereoacuity at least 40 seconds of arc
• no history or signs of any retinal diseases

Participants with macular disorders:

• age 18 or above
• macular disorder present in both eyes
• presence of at least one scotoma within the central 5 degrees of the visual field and with best corrected visual acuity of at least 20/400 in the better-seeing eye
• no foveal island of vision left (i.e. absolute scotoma must include the foveal area)
• cataracts, if present, must be grade 2 or lower according to the Lens Opacity Classification System II

Exclusion Criteria:

Participants with normal vision:

• younger than 18 years of age
• best corrected visual acuity worse than 20/20 in each eye
• cataracts worse than grade 1 according to the Lens Opacity Classification System II
• abnormal contrast sensitivity for their ages
• stereoacuity worse than 40 seconds of arc
• history or signs of any retinal diseases

Participants with macular disorders:

• younger than 18 years of age
• macular disorder absent in at least one eye
• no scotoma within the central 5 degrees of the visual field in the better-seeing eye
• best corrected visual acuity of worse than 20/400 in the better-seeing eye
• foveal island of vision
• cataracts worse than grade 2 according to the Lens Opacity Classification System II

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Microsaccade adaptation; A fixation target will be presented at the center of the display and participants will be asked to keep the target visible at all time. The investigators will measure participants' fixational eye movements continuously and when a microsaccade (small fast eye movements that occur during fixation of a visual target) is detected, the fixation target (a small dot) will jump to a different location, depending on whether the training is to adapt the microsaccades to have smaller or larger amplitudes. With trials, participants would automatically correct for the spatial errors and thus adapting their microsaccade amplitudes. Training consists of 5-6 sessions of training (about 1 hour each). These training sessions will be scheduled weekly if possible, but it is alright if the sessions are not exactly weekly.

Behavioral: Fixation training; Training (adapting) microsaccades during fixation

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fixation stability	Eye positions measured while participants looked at a stationary fixation target for 10 seconds, quantified as the area that captures 68% of eye positions (unit: deg^2).	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Visual acuity	Smallest letter that can be read on an acuity chart (Bailey-Lovie acuity chart). Unit of measurement will be in the logarithm of the minimum angle of resolution (logMAR).	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).
Contrast sensitivity	The faintest (lowest contrast) letter that can be read using the Mars Contrast Sensitivity Test. Unit of measurement will be in the logarithm of the contrast sensitivity ("log units").	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).
Reading performance: Maximum reading speed	Maximum reading speed (unit: words per minute) measured using the MNREAD Acuity Chart (MNREAD Acuity Chart is the name of the instrument that will be used).	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).
Reading performance: critical print size	The smallest print size (unit: logMAR) on the MNREAD Acuity Chart that still allow participants to read at their maximum reading speed.	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).
Orientation judgement accuracy: low spatial-frequency	Accuracy for judging the orientation (tilted to the left or right) of a low spatial-frequency grating. Unit of measurement will be in proportion-correct.	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).
Orientation judgement accuracy: high spatial-frequency	Accuracy for judging the orientation (tilted to the left or right) of a high spatial-frequency grating. Unit of measurement will be in proportion-correct.	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).
Characteristics of fixational eye movements: microsaccade rate	Fixational eye movements during the 10 seconds when participants are asked to fixate a target for fixation stability measurement (primary measurement) will be analyzed. The rate of microsaccades (fast eye movements during fixation) will be measured (unit: number per second).	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).
Characteristics of fixational eye movements: microsaccade amplitude	Fixational eye movements during the 10 seconds when participants are asked to fixate a target for fixation stability measurement (primary measurement) will be analyzed. The amplitude of microsaccades (fast eye movements during fixation) will be measured (unit: degrees).	Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025).

Collaborators and Investigators

• Sponsor: National Eye Institute (NEI)

Study record dates

Study Major Dates

• Study Start (Actual): June 1, 2022
• Primary Completion (Estimated): June 30, 2025
• Study Completion (Estimated): June 30, 2025

Study Registration Dates

• First Submitted: October 29, 2024
• First Submitted That Met QC Criteria: October 31, 2024
• First Posted (Estimated): November 1, 2024

Study Record Updates

• Last Update Posted (Estimated): November 1, 2024
• Last Update Submitted That Met QC Criteria: October 31, 2024
• Last Verified: October 1, 2024

More Information

Terms related to this study

• Keywords: fixational eye movements; microsaccades; saccade adaptation; fixation training
• Other Study ID Numbers: R21EY030253 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: We will report summary results for the group. Some of the outcome measures are health related and we would like to protect the participants' privacy.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No