Ocular Counter Roll

16 February 2022
10 mins
Reading

What is the ocular counter roll test?

The ocular counter roll test is a clinical test to assess otolith function, which takes advantage of a torsional eye tracking algorithm. The test is done with video recording, so it is referred to as a video Ocular Counter Roll test (vOCR). When the head is tilted, the eyes react with a torsional counter roll. This is a called an ocular counter roll (OCR). It is initiated by the vestibular ocular reflex (VOR).

 

Calibration

To perform the test, you should first calibrate the Torsion eye tracker. This allows the algorithm to identify the iris and track the movements of the eyeball.

First select the Ocular Counter roll protocol from the test menu.

List of tests, including Dix Hallpike, Positional, Caloric, vHIT for VORTEQ, VORTEQ AHR, Dynamic Visual Acuity, Saccadometry, Ocular Counter Roll, and vHIT for EyeSeeCam.

Figure 1 – Test Menu

Then select the calibration option.

Figure 2 – Calibration Selection

Once in the calibration menu you can perform 2 tasks:

  1. Calibrate the Torsion tracker
  2. Calibrate the eyes to the TV monitor

First calibrate the Torsion tracker. You can use the Auto Detect button to find the appropriate iris area for tracking. If the white tracking circles are not encompassing enough of the iris you can use the manual slider adjust bars to make small adjustments.

Calibration screen for torsional eye tracking. A list of options to the left, including start calibration, torsion, use default calibration, and advanced settings. Video images of the right and left eyes to the right. For both eyes, the software displays a white cross at the center of the pupil, which is encircled by a white circle. The tracking area for the right eye is set to 62 pixels. The tracking area for the left eye is set to 59 pixels.

Figure 3 – Calibrate Torsion Tracker

When you are satisfied that the tracker is stable around the eyes then use the Set Reference button to finish the calibration.

Figure 4 – Set Torsion Reference

Next, calibrate the eyes to the TV monitor. Instruct the patient to look at each of the five dots. The test will automatically stop when the calibration is completed.

Video eye calibration screen. A list of options to the left, including start calibration, use default calibration, and advanced settings. Video images of the right and left eyes to the right. For both eyes, the software displays a white cross at the center of the pupil. The calibration is complete, visible by green checkmarks in the left, up, right, down, and center positions. Also visible in a graph below, where the the clusters of eye positions are almost perpendicular to the center position.

Figure 5 – Video Eye Calibration

 

Performing the Test

Once the system is calibrated you are ready to begin testing. The TV screen will have a solid background and a center fixation dot. Have the patient look at the dot while you rotate their head. The patient can also rotate their head themselves if you prefer. The instructions are too slowly rotate the head towards the left shoulder and hold it there for 10 seconds. During that time the data is being recorded. After 10 seconds press the enter key and then ask the patient to rotate their head towards the right shoulder. This is called a static ocular counter roll test because the patient is holding their head still in each position.

 

Results

In the results section you will see the torsional nystagmus for clockwise and counterclockwise rotations as the head is tilted to the left and then to the right.

Male clinician stood behind male patient, tilting the patient's head toward the right. The patient is wearing VNG goggles and the clinician is looking toward a large flat screen TV. The results show up to 20 dps of torsional nystagmus for the clockwise rotations.

Figure 6 – (a) Ocular Counter Roll test being performed and (b) Graphical display of test results

You can measure the degree of torsion using the edit functions to add in numerical values.

Figure 7 – Using edit functions to add numerical values to the torsion in the ocular counter roll test.

For further assistance, if needed, please refer to the Instructions for Use and Additional Information manuals.


Presenter

Michelle Petrak
Michelle Petrak, Ph.D., is the Director of Clinical Audiology and Vestibular Research for Interacoustics. Her primary role is development and clinical validation of new technologies in the vestibular and balance areas. She is located in Chicago where she is a licensed private practice clinical audiologist at Northwest Speech and Hearing (NWSPH). Dr. Petrak received her doctorates in Electrophysiology (1992) and Biomolecular Electronics (1994) from Wayne State University and her Masters in Audiology in 1989. Her special areas of expertise include vestibular and balance assessments and management of the dizzy patient. Dr. Petrak is involved with new innovative product developments, clinical evaluations of new protocols, and publishing, teaching, and training on the management of patients with dizziness. She continues to lecture extensively nationally and internationally, and she has numerous articles published in the hearing industry journals. She also participates on the committees for several doctoral students as support for the research projects.

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