Balance Quest
Bertec®

Vision Advantage™

Visual acuity testing
made accurate
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Explore Vision Advantage features

Comprehensive VOR examinations

Extend your evaluation with an assessment of visual acuity during head movement. Vision Advantage provides comprehensive vestibular-ocular reflex (VOR) assessments, helping clinicians and physical therapists determine treatment based on objective data:
  • Head-fixed baseline
  • Visual processing time
  • Loss of visual acuity from head fixed to head moving
  • Visual acuity scores are given for both sides
  • Quantification of the point just before retinal slip

A user-friendly solution

Vision Advantage is equipped with a wireless and lightweight head-worn sensor. As such, head movement is not restricted, and assessment is easier for the clinician.
  • Compact and lightweight
  • Rechargeable battery – offering hours of active testing
  • USB charging
Young woman with her head turned left and eyes fixated to the right.

Computerized VOR training

The patient training software uses computerized VOR training to provide gaze stabilization exercises, with selectable controls for velocity and direction of head movement.

Standardized head movement

The system is easy to use with its auto-calibration of head movement, ensuring accurate results. Head rotation can be measured in yaw, pitch and roll planes.

Protocols

Baseline visual acuity (BLVA)

Baseline visual acuity (BLVA) is a vision exercise that is performed while the head is stationary. The exercise provides a baseline measurement of the smallest optotype a patient can see with their head stationary.

Visual processing time (VPT)

Visual processing time (VPT) assesses how fast a patient can process optotypes. VPT is important to perform before the dynamic visual acuity (DVA) and gaze stabilization tests (GST). If the VPT is longer than 70 milliseconds, then errors in DVA or GST could be related to prolonged processing and not VOR performance. Thus, VPT assesses whether the processing time is short enough to produce accurate results in the following tests.

Dynamic visual acuity (DVA)

Dynamic visual acuity (DVA) is a vision exercise that is performed while the head is moving at a specified constant velocity. During the exercise, the optotype gradually gets smaller to identify the smallest optotype a patient can see with their head moving. This is compared with the baseline measurement to see if head movement causes a change in acuity.

Gaze stabilization test (GST)

The gaze stabilization test (GST) is a vision exercise that is performed while the head is moving at different velocities. During the exercise, the optotype size remains the same while increasing the head velocity. The exercise identifies the maximum head velocity at which a patient can maintain visual acuity.
Person in a chair looking towards a laptop.

How does the testing work in practice?

The visual stimulus is presented on screen and consists of a block letter 'E', also known as an optotype. The stimulus is presented briefly and is randomly rotated. The patient has to identify the orientation of the stimulus and the clinician enters the responses. The tests are scored by accuracy.

Why is the vestibular-ocular reflex (VOR) important?

The vestibular-ocular reflex (VOR) is the dominant system at high head velocities. Thus, the VOR is important for accurate vision, which is integral for postural control and our ability to maintain balance. A well-functioning VOR plays a large part in our ability to perform daily activities that require physical activity.

What might suggest a VOR impairment?

A poor-functioning vestibular-ocular reflex (VOR) is often manifested by visual blurring, dizziness or jumpiness in the visual field. These manifestations usually occur during (head) movement. Vestibular problems such as vestibular neuritis can also lead to a VOR impairment. VOR impairments can also occur prior to head trauma. Finally, from a functional perspective, a change of acuity of three or more Snellen line chart equivalents for head turns in either direction is defined to be indicative of a VOR impairment.

What is analog DVA testing?

Traditional dynamic visual acuity (DVA) testing uses the wall-mounted Snellen eye chart. The patient rotates their head and reads the smallest letters (the lowest line) they can. This is compared with the stationary baseline. A change of acuity of three lines or more is indicative of a vestibular ocular reflex (VOR) impairment.

What are the disadvantages of analog DVA testing?

Traditional dynamic visual acuity (DVA) testing can miss mild impairments or asymmetries. This is due to the fact that the clinician has no assurance of correct head velocity nor any way of isolating responses according to the direction of head movement. In addition, head velocity is zero when changing the direction of head rotation. This can lead to false negatives as vision is clear at zero head movement.

How does Vision Advantage measure head velocity?

Vision Advantage uses a head-mounted sensor to measure head velocity. Optotype stimuli are only presented when the correct velocity is achieved. This enables more precise results, eliminating the influence of other oculomotor systems and operator error. In addition, this creates controlled test conditions where visual acuity is dependent primarily on vestibular-ocular reflex (VOR) function.

Automated protocols

Vision Advantage collects patient responses during the test procedures. It automatically stops testing when the pattern of accuracy indicates that a threshold has been reached. The calculations and reports are generated quickly using a computer, eliminating operator bias and error.

Asymmetries in VOR performance

By using a computer, Vision Advantage can score each direction separately. This allows detection of vestibular-ocular reflex (VOR) asymmetries. The Snellen eye chart method would not be able to detect asymmetries, which could lead to false negatives.

Improve functional outcomes

Vision Advantage provides plenty of important clinical information for physical therapists. The device can be used on the vast majority of patient populations and detects deficits that may have been missed with standard clinical examinations. Vision Advantage can help to establish a treatment plan and in time improve functional outcomes.

The Vision Advantage package

  • Touch-screen laptop computer
  • Head tracker
  • Receiver unit
  • Wireless remote control
Laptop, remote, USB dongle and accessories.

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