The focus for this month is an article written by Jha and colleagues. The intriguing title that caught my eye was: “Video Head Impulse Test in Persons with Blindness: Feasibility and Outcomes.”

The authors began by building a case that good balance requires intact vision, somesthesia, and vestibular-system function. Patients who are blind (i.e., completely blind with no residual vision) must rely on somesthesia (for good static balance) and vestibular function (for dynamic balance, e.g., during ambulation). If vestibular function is compromised, patients must rely on somesthesia alone, which is most effective during static and not dynamic conditions.

The practical question was: Is it possible to record the video head impulse test (vHIT) from a patient who is blind? Accordingly, the authors attempted to record the vHIT in patients with total blindness. The sample was 42 adult subjects (age range 18–40 years of age), with 19 subjects who were blind and 23 age-matched adult control subjects who were not blind.

vHIT was conducted once for the subjects who were blind and three times for the control subjects who were not blind (i.e., there were three recording conditions for the subjects who were blind). Attempts were made to record from all three semicircular canals for each condition.

The three conditions for the control subjects were: Condition 1 (simulated complete blindness, i.e., eyes open in total darkness), Condition 2 (subject tested in daylight, but did not receive a target or instructions), and Condition 3 (the subject was tested in daylight with instructions and a target).

I am not going to give away the results of the study, except to say that the subjects who were blind were able to generate responses to the head impulses, as did subjects who were not blind who were tested in total darkness without a target.

Of note, I would direct any readers who find the topic of this paper interesting (i.e., changes in the vestibulo-ocular reflex (VOR) in simulated conditions) to a paper we (Jacobson et al) published in 2012. The title of that paper was “Suppression of the Vestibulo-Ocular Reflex Using Visual and Non-Visual Stimuli.”

Article published online:
10 October 2022

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