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

National Institutes of Health (NIH)

Status: Active, not recruiting

Conditions: Central Vision Loss From Macular Diseases

Treatments: Behavioral: Fixation training

Study type: Interventional

Funder types: NIH

Identifiers

NCT06670989

R21EY030253 (U.S. NIH Grant/Contract)

Details and patient eligibility

About

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.

Enrollment: 30 estimated patients

Sex: All

Ages: 18+ years old

Volunteers: Accepts Healthy Volunteers

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

Trial design

Primary purpose: Basic Science

Allocation: N/A

Interventional model: Single Group Assignment

Masking: None (Open label)

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30 participants in 1 patient group

Microsaccade adaptation

Experimental group

Description:

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.

Treatment:

Behavioral: Fixation training