How to perform Dynamic Visual Acuity testing

Equipment and hardware

Before we conduct the dynamic visual acuity assessment, let's take a moment just to familiarize ourselves with the hardware. So here on our video goggle, we have our VORTEQ head sensor. We're going to remove that for this test and locate it now on to the headband, which we're going to attach to the patient's head.

If we look at our headband, we've got an area to locate the VORTEQ head sensor, we can slide that so it's securely in situ, and then we're ready to undertake the assessment.

Patient preparation

Okay, now we're ready to conduct the dynamic visual acuity assessment. And let's go through the next couple of steps to set ourselves up to perform this assessment correctly. Firstly, we're going to place the headband on the patient's head.

Now the headband has the head sensor located at the front, we have foam inserts within the headband to hold it securely on the head. And we have an adjustment screw at the back to both loosen and tighten the headband.

Let's place that onto our patient now. So once securely in position, we can just tighten to make sure that the headband is not going to move

Static Visual Acuity

When we're performing the dynamic part of the visual acuity assessment the head is in motion. But to begin with, we're going to test the static visual acuity.

To do that, we're going to give our patients the remote control on which we have some controls where they can indicate the direction of the optotype, which is a letter C, that's going to be displayed to them on the screen.

Once they have that in their hand, and they're ready to begin to test, we then press start. And as soon as we press that the Optotype will be presented.

And as we can see the Optotype is changing in position, and the patient is indicating that they can see it up down right or left. During this test the software is calculating the average static visual acuity for the individual patient.

Horizontal Dynamic Visual Acuity using active head movements

Now that we've performed a static visual acuity assessment, we're introducing the dynamic visual acuity portion of this test. Again, we have the patient using the remote control to indicate the Optotype type direction.

However, the new part to this test is that they're going to have their head in motion whilst the Optotype type is being displayed. We have a bar at the top of the screen.

And that will indicate a green area between 100 and 150 degrees per second of head movement for them to aim for only when they're within this range will the Optotype type be displayed.

We can reassure the patient that if they can keep their head motion, consistent in green than the Optotype will be displayed. Let's start the test. We can see they're achieving the green area. The head is at the correct speed.

And the software is correcting and counting the correct responses. And that's the Test complete. Now that we've completed the right dynamic visual acuity assessment, let's look at another way that we can conduct the test whilst we complete the left dynamic visual acuity assessment.

So for some patients, it can be quite challenging to move the head and press the remote control to indicate the Optotype type direction. For those patients, we can modify the test as follows.

Again, we can ask them to move their head and look at the screen so that they can see the Optotype and keep it in the green. But I as the tester will mark on the remote control the direction of the Optotype when they call it out to me.

So I can take the remote control. And now this is something that I will use to mark the correct response as they call. So again, we'll get our patient ready to conduct the test. We'll press start.

Patient: “Down, down, right down”.

And there we have the test completed. And we can take a look at the results.

Results interpretation

Now we've completed some of our dynamic visual acuity assessments, we can take a moment to look at the results. So here we have some results for Amanda, which we tested in the dynamic visual acuity assessment.

And we have right and leftward dynamic visual acuity results and static. Let's have a look and show, see what the results show us. In the center here in the dark space. We've got the static visual acuity.

When we asked Amanda to start to move ahead and we tested with right dynamic visual acuity, she moved by one line of visual acuity. So that's very much within the normal range.

When Amanda was moving her head towards the left, we saw that the Optotype had to be a little bit larger for her to see it clearly. And that's represented here by about a four-line deviation in acuity with left head with movement.

Now what this could indicate in the patient is somebody who has a functional issue in terms of acuity when their head is in motion. In this instance, when the head is moving to the left.

So that can be a very good starting point for vestibular rehabilitation or gaze stabilization exercises to equalize the acuity when the head is in motion in both directions.

Vertical Dynamic Visual Acuity

Now I'm going to show you a couple of modifications that you can perform through the DVA test when you reach some challenges. So for example, we may want to test the patient by looking at vertical head movement, we've completed the horizontal, but some patients can certainly report symptoms when their head is moving up and down.

For this, we can do the same test. But now we would instruct the tester as Amanda is doing to move their head up and down whilst the Optotype is being presented and we would score in the same manner as we did previously.

Dynamic Visual Acuity using passive head movements

One of the other challenges that we can sometimes have in DVA testing is so far, we've looked at active head movement. And by that, I mean that the patient is moving their head independently as Amanda is doing now.

But for some patients, that can be quite tricky. So as a tester, what we can do in that circumstance is doing passive head movement.

And to do that, we would come and stand behind the patient, we would have the software running with the Optotype being present, we would need them to score the direction of the optic type, we would then oscillate their head at the desired speed, which is an average of 100 degrees per second.

Changing head speed (frequency) 

The third option that we can look at as a modification is in some patients, they are very high performing. We may want to test this DVA at a different frequency, we can very quickly do that in our protocol settings.

If we then navigate back to home, we can come into configuration, look at our protocol management, select our DVA test, come into edit. Primarily, we probably want to do this with the horizontal movements to begin, and then we can see in our threshold check here we can put this at two hertz.

And now we can have a test at a much higher frequency of head movement. We then just come out of the settings conduct test again. And then we can look and compare the results at the two different frequencies of head movement.