13 Dynamic Visual Acuity (DVA)

Attachment 13

Dynamic Visual Acuity (DVA)

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Name of test: Dynamic Visual Acuity (DVA) 1
Estimated time burden: 10 minutes
Number of items: One static visual acuity task plus two dynamic visual acuity tasks
Materials:
Dynamic visual acuity equipment: rate sensor on data acquisition board (DAQ, small black box),
attached to headgear participant wears; long USB cable to plug DAQ into computer
Laptop computer and 19” monitor
Laminated card with HOTV letters (for ages 3-7 only)
Chair (with booster seat and/or KaboostTM for smaller children)
Two small tables or one long table
Isopropyl alcohol wipes or spray (for disinfecting headgear for each new participant)
Description:
This activity is intended to measure visual acuity (static) as well as deficits of the vestibular
ocular reflex in adults and children. A brief training procedure is included in the test to
ascertain that the participants, both child and adult, know what needs to be done to
complete the assessment. If they do not succeed in the training, testing can be
discontinued.

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Set-up: The cable from the DAQ should be already plugged into your laptop’s
USB port. Be sure it is plugged in before launching this test within the
software. The headgear is placed on the participant during the dynamic
acuity testing (after static testing is completed, as described below).
Note: Before testing begins, ascertain if the participant wears corrective lenses
for distance, and ensure he/she is wearing them. If necessary, ask the
participant if he/she wears glasses or contact lenses for distance vision. If
the participant does wear lenses but indicates he/she has forgotten them
(or does not have them for any reason), the examiner may choose to
continue testing or not; it is the examiner’s discretion. However, if the
participant requires a very strong correction, testing will not likely be valid.
The examiner should note any such irregularities and, if testing is
completed, should interpret results with caution.
Testing: Testing will use different sets of optotypes (images) for children and
adults. For both the dynamic and static parts of this measure, the
participants are to be seated 12.5 feet away (at eye level) from the
viewing monitor. The monitor should be at eye level as shown in the
picture below (note: symbols behind monitor should not be part of adult
setup).
Administration Instructions for ages 3-7 — Static Visual Acuity:
Because a number of children may not be able to name one or more of the
letters HOTV, a laminated card is also used with young participants,
allowing them to point to what they saw on the screen without
verbalizing. The accompanying adult may sit next to the child and report
to the examiner which letter the child chose. Before static testing begins,
there is a training sequence and then practice items.

Training:
The examiner should have the child sit in the chair where visual acuity testing will
be administered, then say: “Now we are going to do an activity that shows
us how well you can see pictures on the TV screen. Sometimes you will do
this as you sit like you are now, and then you will do it again with your
head moving.” Hand the child the laminated card and say: “Everything
you will see is shown on this card. This is a picture of an H, this is a picture
of an O, this is a picture of a T, and this is a picture of a V (point to each
letter while naming). Now, you try to name the pictures.” Encourage the
child to name the letters as best he/she can. If the child names all four
letters correctly, say, “Good job.”

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If any are named incorrectly, point to each letter and say only one time as
before: “This is a picture of an H, this is a picture of an O, this is a picture of
a T, and this is a picture of a V.” (Because letter naming is not required to
complete the test, it is OK if the child does not correctly name each letter.
Encourage the child’s efforts without providing negative feedback.) Then
say, “Let’s do some more.”
Say: “You are going to look on this screen (point to monitor); then, you will see a
picture (for children who clearly know the alphabet, it is OK to say “letter”
instead of “picture”). Each time, I want you to tell me or point on this card
to what you saw on the screen. If you are not sure, it is OK to guess. Are
you ready to start? Let’s begin.”

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Practice:

Opening screen for Practice 1

The examiner should present one set of practice static acuity trials (4) at 20/400.
a. If 3 or more correct, continue to static testing.
b. If the child misses 2 or more of 4, review the ‘pointing chart’ and ask
him/her to identify (either orally or by pointing) the optotypes (‘pictures’),
namely the letters HOTV. If all are done correctly, see b1. If child cannot
correctly identify the optotypes on the HOTV set, more training will be
needed before testing can continue.
1. Proceed to a second practice trial set. If 3 or more of 4 are done
correctly, proceed to live static testing. If not, repeat (third practice
trial set). If 3 or more correct, begin static test. If 2 or more are
incorrect, stop test since this is the third practice trial (see b2).
2. Practice trials should be limited to a total of 3 sets. If after 3 trials the
criterion of 3 or more of 4 correct is not achieved, then stop the test.

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Static Testing:
The examiner should say: “You did great. Now we will see how well you can see
pictures as they get smaller. They will get smaller – just tell me what you
see, ok?”
The examiner should click on Start Test on the examiner’s screen. Each time a
letter is displayed, say, “Tell me or point to what you see.”
It is the examiner’s job to use the computer to record (click on) whether the
response was correct or incorrect. Simply note the child’s verbal or
pointing response, compare it to the correct answer listed on the
examiner’s screen, and score it accordingly. The next item will not appear
until the examiner has scored the item currently on screen. If the child is
trying but struggling to verbalize the letters, remind him/her that pointing is
OK by saying, “You can show me what you see.”
The test will progressively present smaller letters if the child answers correctly or
larger ones if the child is answering incorrectly, until an acuity score is
established. The test will automatically end when the computer has
calculated the acuity score. The examiner should click the Next button to
move on to the next section.
Note: If a child’s static score is equivalent to 20/400 vision or worse, the program
does not allow the examiner to administer the Dynamic Visual Acuity test
portion, because the results would not be valid. Specifically, if a child
scores this poorly on the static portion of the test, it suggests there are

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serious uncorrected distance vision deficits. Please suggest follow-up
evaluation by a vision professional.
Administration Instructions for ages 3-7 — Dynamic Visual Acuity:
The examiner needs to explain to the participant that he/she must wear the
headgear (“hat”) to enable the computer to know if his/her head is
turning. For young children, it may be helpful to embellish the headgear
with decorations, to encourage them to wear it. Show the headgear with
rate sensor to the child, saying something like the following (adapt as
needed): “Now we are going to do the same activity, but this time you will
move your head back and forth as if saying NO. If you move it just right,
the letters will appear. This special hat will be on your head so the
computer can know if your head is moving just right. If it is, the pictures
will show up!” Can you help me put it on your head?” Place the
headgear securely on the child’s head, making sure it is comfortable and
correctly adjusted.
Training
When the headgear is properly positioned, say, “To make a picture appear on
the screen, you need to move your head, like you are saying ‘no,’ or ‘uhuh.’ Watch me”. Demonstrate for the child and then say, “Now you try it.
Shake your head like you are saying ‘no.’” Give appropriate feedback
until the child demonstrates an understanding of the required motion.
“This time when you shake your head, a picture will flash on the screen. I want
you to tell me, or point to, what you see each time. It is OK to make your
best guess. When you see the picture flash on the screen, stop shaking
your head.”
Using a practice trial at 20/400 size, sit with child and have him/her make the
pictures appear with the correct head movement. The examiner can
judge the correctness of the movement by watching the moving vertical
bar on the computer screen and whether it is in the green range or not
(between the numbers 180 and 250). The examiner may need to
demonstrate again; the purpose of this practice is to make sure the child
has learned to move his/her head correctly. It is important that the size of
the head movement is not too large. If so, the child will not be able to see
the letter. The movement amount should be small and quick (like shaking
the head no). Try to make this part fun. If done correctly, give the child
praise. If not correct, the examiner should demonstrate while directly in
front of the child.

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Dynamic Visual Acuity training screen

Practice:
Once the child has learned to move his/her head correctly, there is a practice
series with the HOTV letters at size 20/400. The child receives 10 trials (each
trial involves up to 3 flashes of each letter) and is asked to identify the
letters by either pointing to or saying the letters. The child needs to
achieve 60 percent (6 of the 10 trials) correct to continue with testing.
When 5 practice trials are incorrect, the test is automatically discontinued.
This logic is built into the computer program. Specifically, as soon as the
child gets 6 correct, the program moves on. Similarly, if the child gets 5
incorrect, the administration stops. The practice items will measure
leftward head rotation, as the testing itself begins with rightward rotation.

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Dynamic Visual Acuity practice screen

Dynamic Testing:
Click on the Start button and say, “Now we are going to do some more of these.
Ready? Go ahead.”
The letters will begin at 3 sizes above the achieved static score and will become
progressively smaller or larger, depending on the child’s performance. A
given letter will flash up to 3 times after the head rotation. The child
should be encouraged not to answer until he/she is certain which letter
flashed; after 3 letter flashes, the letter will no longer appear, regardless of
head movement.
The examiner should prompt the child each time by saying something like, “Go
ahead,” or “Now shake your head no.” If the child is trying but struggling
to verbalize the letters, remind him/her that pointing is OK by saying, “You
can show me what you see.”
The examiner should provide
encouragement and praise regardless of whether the letter identified is
correct, so that the child will continue.
The examiner should use the computer to record whether the response was
correct or incorrect by clicking either the Yes or No button. The next item
will not appear until the examiner has scored the item currently on screen
(but will be available to appear – prompted by the child’s head-shaking –
after the examiner has scored the previous item).

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If the child has not used all 3 trials and has not responded or seems uncertain
about his/her answer, the examiner should prompt the child by saying
something like, “Go ahead,” or “Now shake your head no again.” If the
child has used all 3 trials and/or is trying but struggling to verbalize the
letters, remind him/her that pointing is OK by saying, “You can show me
what you saw.”
The examiner should remind the child as needed that after he/she says or points
to a letter in response to what flashed on the screen, he/she should stop
the head-shaking and wait for the examiner to indicate that it is time for
the next item (since the letter flashes up to 3 times, the same letter will
flash if the child continues to shake his/her head until the examiner enters
the child’s response; this must be carefully managed by the examiner).
If the child sees the presentation of a letter multiple times (up to 3 are possible)
and provides different responses, the examiner should go with the
preponderance of responses given by the child. In a case where the child
gives different responses each time, the examiner should score the child’s
last response to the flashing letter presentation. The test will progress and
automatically end when the child reaches the discontinue criterion, or
he/she has correctly identified the smallest-size letters presented.

The test is divided into Part 1 (right) and Part 2 (left), meaning that the letter will
only flash for a rightward (Part 1) head rotation and then leftward (Part 2)
head rotation. However, the child makes head rotations to both sides (as
if saying “No”), not in one direction only, so there is no change in
instructions to the child. When the test is completed, the examiner’s
screen and the letters will no longer flash.
The computer automatically ends the test after it has determined the dynamic
acuity score; the examiner then says: “We’re all done with this activity.”
Administration Instructions for ages 8-85 — Static Visual Acuity:
The examiner should have the participant sit in the chair where visual acuity
testing will be administered, then say:
“Now we are going to do an activity where you will tell me what letters you see
on the screen. You are going to look on this screen (point to monitor) and
you will see a letter. Each time, I want you to tell me the letter you saw on
the screen. If you are not sure, it is OK to guess. The letters will get smaller
and smaller until you cannot really see them. That is ok. We are trying to
determine how small they can get before you cannot see them. Are you
ready to start? Let’s begin.”

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Static Testing 1 (with glasses or contact lens if usually worn for distance vision):

Opening screen for Static Visual Acuity Test

The examiner should click on the Start button on the examiner’s screen. Each
time a letter is displayed, say, “Tell me, what letter is this?” (At the
examiner’s discretion, this can be replaced by: “Go ahead” after a few
letters have been displayed.) It is the examiner’s job to use the computer
to record whether the response was correct or incorrect by clicking either
the Yes (correct) or No (incorrect) button. Simply note the participant’s
response, compare it to the correct answer listed on the examiner’s
screen, and score it accordingly. The next item will not appear until the
examiner has scored the item currently on screen (but it will appear
immediately after the examiner clicks Yes or No).
The test will progressively present smaller letters if the participant answers
correctly and larger ones if the participant answers incorrectly, until an
acuity score is found. The test will automatically end when the computer
has calculated the acuity score. The examiner should click the Next
button to move on the next section.

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Static Acuity last screen
Note: If a participant’s static score is equivalent to 20/400 vision or worse, the
program does not allow the examiner to administer the Dynamic Visual
Acuity test portion, because the results would not be valid. Specifically, if
a participant scores this poorly on the static portion of the test, it suggests
there are serious uncorrected distance vision deficits.
For participants who wore glasses, the examiner should ask: “Are your glasses
progressive or multifocal?” if the answer is yes, then the examiner should
proceed with Static Testing 2; if the answer is no, the examiner should
proceed to testing Dynamic Visual Acuity.
Static Testing 2 (only for those participants with glasses that are multifocal or that
have progressive lens):
Say: “Now we are going to do this test again, this time without your glasses.”
The examiner should click on the Start button on the examiner’s screen. Each
time a letter is displayed, say, “Tell me, what letter is this?” (At the
examiner’s discretion, this can be replaced by: “Go ahead” after a few
letters have been displayed.) It is the examiner’s job to use the computer
to record whether the response was correct or incorrect by clicking either
the Yes (correct) or No (incorrect) button. Simply note the participant’s
response, compare it to the correct answer listed on the examiner’s
screen, and score it accordingly. The next item will not appear until the

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examiner has scored the item currently on screen (but it will appear
immediately after the examiner clicks Yes or No).
The test will progressively present smaller letters if the participant answers
correctly and larger ones if the participant answers incorrectly, until an
acuity score is found. The test will automatically end when the computer
has calculated the acuity score. The examiner should click the Next
button to move on the next section.
Administration Instructions for ages 8-85 — Dynamic Visual Acuity:
NOTE: For participants with glasses that are multifocal or that have progressive
lens, this part of the testing should be done without glasses. Other
participants wearing single-vision lenses should continue to wear them for
Dynamic Visual Acuity assessment
The examiner needs to explain to the participant that he/she must wear the
headgear to enable the computer to know if his/her head is turning.
Show the headgear with rate sensor to the participant, saying something
like the following (adapt as needed): “Now we are going to do some
more, but this time, you need to wear this special headband to make the
letters appear. May I put it on your head now?”
Place the headgear securely on the participant’s head, making sure it is
comfortable and correctly adjusted (rate sensor should be on right side of
head, with headgear adjustment knob at the back of the head; see
photo on page 1).
When the headgear is properly positioned, say, “To make a letter appear on the
screen, you need to move your head, like you are saying ‘no.’ Watch me.
Demonstrate for the participant and then say, “Now you try it. Shake your
head like you are saying ‘no.’” Before dynamic testing begins, there is a
training sequence and then practice items.
Training:
Using a practice trial at 20/400 size, the participant make the letters appear with
the correct head movement. The examiner can judge the correctness of
the movement by watching the moving vertical bar on the computer
screen and whether it is in the green range or not (between the numbers
180 and 250). If the participant is not making the correct movement, the
examiner may need to demonstrate again; the purpose of this training is
to make sure the participant has learned to move his/her head correctly.

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Dynamic Visual Acuity training screen
Practice:
Once the participant has learned to move his/her head correctly, there is a
practice series with the letter size set at 20/400.
Now the examiner should say: “This time when you shake your head, a letter will
flash on the screen. I want you to tell me what you see each time. It is OK
to make your best guess. When you see the letter flash on the screen and
after you have told me your answer, stop shaking your head.”
The participant receives 10 trials (each trial involves up to 3 flashes of each
letter) and is asked to identify the letters by saying them out loud. The
participant needs to achieve 60 percent (6 of the 10 trials) correct to
continue testing.
When 5 practice trials are incorrect, the test is
automatically discontinued. This logic is built into the computer program.
Specifically, as soon as the participant gets 6 correct, the program moves
on. Similarly, if the participant gets 5 incorrect, the administration stops.
The practice items will measure leftward head rotation, as the testing itself
begins with rightward rotation.

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Dynamic Visual Acuity practice screen
Dynamic Testing:
Click on Start Test and say, “Now we are going to do some more of these. The
letters will be smaller than the one we just practiced with. Ready? Go
ahead.”The letters will begin at 3 sizes above the achieved static score
and will become progressively smaller or larger, depending on the
participant’s performance. A given letter will flash up to 3 times after the
head rotation. The participant should be encouraged not to answer until
he/she is certain which letter flashed, although after 3 letter flashes, the
letter will no longer appear, regardless of head movement.
The examiner should use the computer to record whether the response was
correct or incorrect by clicking either the Yes or No button. The next item
will not appear until the examiner has scored the item currently on screen
(but will be available to appear – prompted by the participant’s headshaking – after the examiner has scored the previous item). If the
participant does not appear to have seen the letter flash or is in any way
unsure of his/her response, allow him/her up to the full 3 attempts at the
letter. The examiner should prompt the participant each time by saying
something like, “Go ahead,” or “Now shake your head no again.”

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Dynamic Visual Acuity Test – Part 1
The examiner should remind the participant as needed that after he/she says a
letter in response to what flashed on the screen, he/she should stop the
head-shaking and wait for the examiner to indicate that it is time for the
next item (since the letter flashes up to 3 times, the same letter will flash if
the participant continues to shake his/her head until the examiner enters
the participant’s response; this must be carefully managed by the
examiner).
If the participant sees the presentation of a letter multiple times (up to three are
possible) and provides different responses, the examiner should go with
the preponderance of responses given by the participant. In a case in
which the participant gives different responses each time, the examiner
should score the participant’s last response to the flashing letter
presentation. The test will progress and automatically end when the
participant reaches the discontinue criterion, or he/she has correctly
identified the smallest-size letters presented.
The test is divided into Part 1 (right) and Part 2 (left), meaning that the letter will
only flash for a rightward (Part 1) head rotation and then leftward (Part 2)
head rotation. However, the participant makes head rotations to both
sides (as if saying “No”), not in one direction only, so there is no change in
instructions to the participant. When the test is completed, the examiner’s
screen and the letters will no longer flash.

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The computer automatically ends the test after it has determined the dynamic
acuity score; the examiner then says: “We’re all done with this activity.”