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

N/AActive Not RecruitingNCT06670989

National Eye Institute (NEI)30 enrolled

Overview

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 Type

INTERVENTIONAL

Allocation

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

Conditions

Central Vision Loss From Macular Diseases

Eligibility

Sex: ALLMin age: 18 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

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).

Time frame: 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 Outcomes

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).

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").

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).

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.

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.

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.

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).

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).