Gaze Stability Test

15 February 2022
10 mins
Reading

What is the gaze stability test?

The gaze stability test measures the patient’s ability to maintain a steady gaze on an object at various angles without the eye generating extraneous movements (i.e. square wave jerks or nystagmus). The inability to maintain a steady gaze is an indication of either a central or peripheral vestibular system lesion. Gaze positions tested are: center (straight ahead), gaze left, gaze right, gaze up and gaze down.

 

Patient instructions

“You will see a green dot on the screen. Simply look at the dot. If the dot moves, follow it with your eyes only. Try not to move your head.”

 

Normal gaze stability results

A patient with normal gaze ability will produce a tracing that is virtually a straight line once the eyes are fixated on the target. The right eye is represented by the red line and the left eye by the blue line. If nystagmus is present it will be identified by triangles on the eye position graph to represent each detected nystagmus beat. The average slow phase velocity value(s) will be plotted in the bar graphs to the right of the tracings. When the average slow phase velocity exceeds the threshold value of 6⁰/sec, the bar graph will be shaded grey and a red diamond will appear near the bar graph to indicate an out of threshold response.

Gaze stability results overview, including gaze center, gaze right 30 degrees, gaze down 20 degrees, gaze left 30 degrees, and gaze up 20 degrees. For all subtests, the blue curve for eye position follows the yellow curve for target position almost perfectly.

Gaze test showing normal response for all gaze angles (center, left, right, up and down)

 

Abnormal gaze stability results

An “abnormal” gaze tracing might present itself in several ways. A patient may present with square wave jerks, nystagmus, or gaze decay. Below are examples of abnormal tracings:

Gaze stability results overview, including gaze center, gaze right 30 degrees, gaze down 20 degrees, gaze left 30 degrees, and gaze up 20 degrees. For gaze right and left 30 degrees, horizontal left, the blue curve for eye position is jagged, indicating nystagmus. For right 30 degrees, the average slow phase velocity of the nystagmus is 6. For left 30 degrees, the average slow phase velocity of the nystagmus is 7. The nystagmus peaks are marked with a blue triangle, and the failed subtests are flagged with a red diamond.

Gaze test showing bilateral gaze-evoked nystagmus

Gaze stability results overview for gaze down 20 degrees. For vertical left, the blue curve for eye position is jagged, indicating nystagmus. The average slow phase velocity of the nystagmus is 6. The nystagmus peaks are marked with a blue triangle, and the subtest is flagged with a red diamond.

Gaze test showing down-beating nystagmus on gaze down 20⁰

 

Conclusion

Gaze testing is the ONLY test of the four ocular tests in which an “abnormal” result could be generated either from the peripheral vestibular system or from the central vestibular system. For a complete discussion of differential diagnosis using the gaze stability test, refer to:

Jacobson, GP, and Shepard, NT. Balance Functional Assessment and Management, 2nd Ed. San Diego; Plural Publishing, 2015

*NOTE: This is intended only as a guide, official diagnosis should be deferred to the patient’s physician.


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