Real-time Acoustic Biofeedback for Enhancing Fixation Stability: A Proof-of-concept Study to Improve Ophthalmic Imaging Diagnostic Quality

The goal of this Proof of Concept Feasibility Study is to improve the fixation stability in patients with fixation loss due to blindness or central vision loss using a patented acoustic real-time feedback device. The main questions it aims to answer are:

• Fixation guidance - can real-time acoustic biofeedback improve the fixation in healthy patients as well as patients with fixation loss?
• Optimization of fixation guidance - testing of different stimuli to optimize an acoustic training protocol.
• Optimization of imaging acquisition - testing improvement of both imaging quality and acquisition time using the acoustic feedback tool.

Primary endpoints: Fixation stability (in BCEA and distance from target center), fixation duration, time to fixate. We test fixation in two angles: neutral position (0°) and at 15° eccentricity. We compare three conditions: visual target only, combined visual and auditory feedback, and auditory feedback only.

Secondary endpoints: adaptation and training effects over time, exhaustion measured in a Likert scale. We measure changes of pupil diameter in response to acoustic and visual stimuli. We also compare efficacy between healthy subjects and subjects with fixation loss and compare efficacy between the three conditions.

For the proof-of-concept part of our study, patients are asked to fixate on a target point in a darkened room and keep up fixation for 10 seconds. We record patients eye movements with near-infrared-lighting and a camera. There are three blocks for each condition (visual, auditory, combined), each block consists of 10 trials per eye and per angle. In between each set of trials, patients are asked to rate their subjective exhaustion on a Likert scale. At the end of each recording session, we ask patients for their subjective feedback on which condition was easiest to keep up fixation, whether auditory stimuli were sufficient and open-ended questions on potential improvements of the setup.

An ethics-approved extension phase is planned to further optimize device parameters and assess performance in a clinical setting. We validate the findings of our proof-of-concept study and optimize the device settings by adding the acoustic fixation device to our imaging devices. We will compare the results to answer the question whether the acoustic fixation device will lead to an improved imaging quality and acquisition time.

Inclusion criteria

Healthy participants:

• minimum age of 18 years
• no neurological or ophthalmological disease
• ability to perceive auditory feedback
• normal vision
• consent to participate in study

Patients:

• minimum age of 18 years
• existing ophthalmological diagnosis of fixation deficite or loss
• ability to perceive auditory feedback
• consent to participate in study

Exclusion criteria

• lack of ability to consent to participate in study
• reduced cooperation during examination or recording
• inability to perceive auditory feedback
• age below 18 years
• patients with nystagmus or inability to move eyes
• opacity of cornea or other ocular structures preventing successful eye tracking
• inability to communicate