WEBVTT

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Teller Acuity Cards
are used to test visual acuity

00:00:08.600 --> 00:00:11.200
in young children
and those with disabilities

00:00:11.200 --> 00:00:13.266
who cannot be tested
with standard letter

00:00:13.266 --> 00:00:16.066
or symbol acuity tests.

00:00:16.066 --> 00:00:18.232
The stimulus
on a Teller Acuity Card

00:00:18.233 --> 00:00:20.733
is a high contrast black
and white pattern

00:00:20.733 --> 00:00:23.099
of stripes called a grating.

00:00:23.100 --> 00:00:25.166


00:00:25.166 --> 00:00:28.466
The gratings range
from very coarse to very fine,

00:00:28.466 --> 00:00:30.132
in order to test visual acuity

00:00:30.133 --> 00:00:32.666
from very low vision to normal.

00:00:32.666 --> 00:00:34.166


00:00:34.166 --> 00:00:36.866
Most rectangular cards
have a single grating

00:00:36.866 --> 00:00:39.432
printed off to one side
of the center.

00:00:39.433 --> 00:00:41.833
Printing the grating
to one side of the card

00:00:41.833 --> 00:00:44.666
allows it to be presented either
on the left

00:00:44.666 --> 00:00:45.866
or the right.

00:00:45.866 --> 00:00:46.932


00:00:46.933 --> 00:00:47.799
An additional card

00:00:47.800 --> 00:00:51.100
has a grating nearly covering
one-half of the card.

00:00:51.100 --> 00:00:54.200
This card
is called the low vision card.

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00:00:56.166 --> 00:01:00.266
The final card is a blank, gray card
without a grating.

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Grating values are specified

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by the width
of their black and white bars.

00:01:06.300 --> 00:01:10.400
A single black and white pair
of bars is called a cycle.

00:01:10.400 --> 00:01:12.000
Grating sizes are specified

00:01:12.000 --> 00:01:15.200
by the number of black
and white cycles per centimeter.

00:01:15.200 --> 00:01:16.466


00:01:16.466 --> 00:01:18.366
The metric cycles per centimeter

00:01:18.366 --> 00:01:21.399
is converted to visual acuity based
on the distance

00:01:21.400 --> 00:01:24.400
of the Teller Acuity Card grating
from the patient,

00:01:24.400 --> 00:01:28.100
and is specified as cycles
per degree.

00:01:28.100 --> 00:01:31.333
The cycles per degree measure
is the appropriate specification

00:01:31.333 --> 00:01:33.133
for grating acuity.

00:01:33.133 --> 00:01:34.399


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If necessary,
grating acuity can be converted

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into conventional Snellen notation,

00:01:39.700 --> 00:01:42.566
which may be more appropriate
for certain reporting.

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Each Teller Acuity Card
has labels on the back

00:01:47.133 --> 00:01:49.999
showing the grating size
in cycles per centimeter,

00:01:50.000 --> 00:01:54.366
and the conversions to acuity based
on three test distances.

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The labels on the back
of the card are placed

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so the examiner has no information

00:01:58.433 --> 00:02:00.533
about the right-left position
of the grating

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from viewing the back of the card.

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The primary principle
of a Teller Acuity Card

00:02:05.933 --> 00:02:08.766
is that if a patient sees a grating
on the grey background,

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she will look at the grating.

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If the grating bars cannot be resolved
or seen by a patient,

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the grating should match
the grey background perfectly,

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mimicking the blank card.

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The examiner's task
in testing Teller Acuity Cards

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is to determine the finest grating

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that the patient sees or detects.

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This gives the patient's
visual acuity.

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This requires testing a series
of gratings,

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starting from relatively wide
and easily seen

00:02:36.733 --> 00:02:38.699
to progressively finer gratings,

00:02:38.700 --> 00:02:42.433
until the patient
no longer responds consistently.

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The recommended clinical method
of testing is

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for the examiner
to present a single grating

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a sufficient number of times
to judge whether the patient

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sees that grating.

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As there are only two locations
where the grating can appear,

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an examiner has a 50% chance
of guessing the correct location

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without even watching the patient.

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[no audible dialog]

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This means that gratings
may need to be shown multiple times

00:03:04.700 --> 00:03:07.933
if the patient's responses
are not definitive.

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Typically, the patient's responses
will be definitive

00:03:11.266 --> 00:03:14.899
when the grating is coarse
and above their acuity level.

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However, a finer grating
that is more difficult

00:03:17.533 --> 00:03:20.733
for the patient to see
may lead to more subtle responses

00:03:20.733 --> 00:03:22.833
and require more presentations.

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It is up to the examiner
to determine

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how many presentations
she needs to be confident

00:03:28.466 --> 00:03:30.799
of the patient's visual acuity.

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[no audible dialog]

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There is a small hole in the center
of the Teller Acuity Card

00:03:38.033 --> 00:03:40.833
through which the examiner
or tester can view the patient

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as they look at the gray card
and the grating.

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The examiner can also view
the patient's responses

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to the gratings
by looking over the top of the card.

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[no audible dialog]

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The examiner
is able to change the card position

00:03:53.400 --> 00:03:56.700
to judge where the grating
is located, right or left,

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based on the patient's
visual behaviors,

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such as looking
towards the right or left,

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or pointing or other behaviors.

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The card is shown to the patient

00:04:06.433 --> 00:04:09.133
by an examiner holding it
along the edges.

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They should not be touching
the front surface of the card.

00:04:12.733 --> 00:04:15.066
If the examiner uses fingers
to hold the card,

00:04:15.066 --> 00:04:16.999
rather than the palm of the hand,

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fingertips should not touch
the front,

00:04:18.900 --> 00:04:22.166
except possibly within one inch
of the edge of the card.

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The examiner shows the card
in one position

00:04:25.633 --> 00:04:27.966
and makes a judgment as
to where the grating is

00:04:27.966 --> 00:04:30.199
based on the patient's behavior.

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In this case, the examiner
judges the grating to be on her left,

00:04:33.900 --> 00:04:35.500
the patient's right.

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The examiner
then rotates the card 180 degrees.

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Now, if the infant's behavior
indicates seeing the grating,

00:04:44.266 --> 00:04:48.199
the examiner should judge
the grating is on the infant's left.

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The examiner
should not always rotate the card

00:04:50.400 --> 00:04:53.100
180 degrees between presentations,

00:04:53.100 --> 00:04:56.866
as some patients
may anticipate the gratings position.

00:04:56.866 --> 00:04:59.899
Instead, the examiner
should show the grating frequently

00:04:59.900 --> 00:05:02.100
in the same location.

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The examiner is being shown
holding the cards

00:05:04.300 --> 00:05:06.200
in a horizontal orientation,

00:05:06.200 --> 00:05:08.000
which is the standard
and most common way

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of presenting Teller Acuity Cards.

00:05:10.133 --> 00:05:13.633
However, the cards may be held
in a vertical orientation,

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with the grating either on the upper
or lower part of the card.

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This can be a useful method
for testing patients

00:05:19.366 --> 00:05:22.999
with nystagmus or strabismus.

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During testing,
patients may wish to touch the grating

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or may invertently touch it
when trying to point to the grating.

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This should be avoided
by giving the child a soft toy to hold

00:05:33.733 --> 00:05:36.199
and point toward the grating.

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To keep the patient's attention,

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the examiner can interact with
and reinforce the patient

00:05:41.733 --> 00:05:44.066
for finding the grating location.

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[no audible dialog]

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Presenting a grating that has been
seen previously by the patient

00:05:49.866 --> 00:05:52.232
can reestablish interest
in the testing

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and also reassure the examiner
that the infant

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is still attending
to the gratings.

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[no audible dialog]

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What behaviors
does the examiner use

00:06:01.633 --> 00:06:04.933
to judge whether the patient
sees a grating?

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The examiner must be aware of any

00:06:06.666 --> 00:06:08.799
and all patient cues and behaviors

00:06:08.800 --> 00:06:12.100
that indicate the location
of the grating.

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Typically, in young infants,
a strong fixation response

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to one side of the card,
presumably at the grating,

00:06:18.933 --> 00:06:23.199
and then to the other side
when the card is rotated 180 degrees,

00:06:23.200 --> 00:06:26.433
indicates the infant detects
that grating.

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Finer gratings may not be
as strongly fixated,

00:06:29.200 --> 00:06:33.633
yet will still elicit a consistent gaze
from the young infant.

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Older infants and toddlers
may give brief glances to each side,

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which are accepted as detection,

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because the glance
is direct and clear,

00:06:41.000 --> 00:06:44.200
and repeated
on subsequent presentations.

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Some mature toddlers
and young children

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may point to one side,

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especially if prompted by the examiner,
such as,

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"Where did the stripes go?"

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This section illustrates
the complete sequence

00:06:56.766 --> 00:07:01.299
of testing a child's visual acuity
with Teller Acuity Cards.

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Young patients are usually seated
on their parent's lap,

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and the parent or holder
should be cautioned

00:07:07.000 --> 00:07:10.066
not to give the child any guidance
during testing.

00:07:10.066 --> 00:07:11.199


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Based on the patient's age,
determine the start card for testing.

00:07:15.333 --> 00:07:18.933
Consult the Teller Acuity Card
Reference and Instruction Manual.

00:07:18.933 --> 00:07:19.999


00:07:20.000 --> 00:07:22.166
If the patient
is visually impaired,

00:07:22.166 --> 00:07:24.499
a coarser grating than
that based on age

00:07:24.500 --> 00:07:26.700
may be needed for the start card.

00:07:26.700 --> 00:07:28.000


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Distance of the card
from the patient's face

00:07:30.066 --> 00:07:32.299
also depends upon age.

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Consult the Teller Acuity Card
Reference and Instruction Manual.

00:07:36.366 --> 00:07:41.266


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The examiner
measures the test distance

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from the patient's eyes
to the position the card is held.

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For the 55-centimeter distance,
the length of the card

00:07:49.700 --> 00:07:51.200
is an exact measure.

00:07:51.200 --> 00:07:52.366


00:07:52.366 --> 00:07:55.732
For the 38-centimeter distance,
used with young infants

00:07:55.733 --> 00:07:57.999
and patients with limited vision,

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a measuring tape can be used.

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Or, a convenient measure
is the distance

00:08:02.700 --> 00:08:05.433
between the examiner's elbow
and fingers,

00:08:05.433 --> 00:08:07.499
with fingers either close or open,

00:08:07.500 --> 00:08:10.266
depending
on the examiner's arm length.

00:08:10.266 --> 00:08:13.599
This needs to be measured
before testing.

00:08:13.600 --> 00:08:15.533
For 84-centimeter distance,

00:08:15.533 --> 00:08:18.999
used with older children,
a measuring tape is needed.

00:08:19.000 --> 00:08:21.400
Alternatively,
a measuring tape can be placed

00:08:21.400 --> 00:08:24.800
on a table surface, adjacent
to the patient and the examiner,

00:08:24.800 --> 00:08:27.600
with marks for each distance.

00:08:27.600 --> 00:08:29.966
The examiner should check
the test distance periodically

00:08:29.966 --> 00:08:32.632
during the testing,
as some patients will lean forward

00:08:32.633 --> 00:08:34.499
to get closer to the gratings,

00:08:34.500 --> 00:08:37.800
especially when they
become finer and more difficult to see.

00:08:37.800 --> 00:08:39.100


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Set up the cards in two stacks
with the grading face down

00:08:42.200 --> 00:08:44.933
on a soft, clean surface.

00:08:44.933 --> 00:08:47.233
The card labels are up.

00:08:47.233 --> 00:08:49.833
One stack is for gratings
the patient has not seen,

00:08:49.833 --> 00:08:51.833
or will not be tested on,

00:08:51.833 --> 00:08:54.699
and the other stack is
for cards the patient has seen

00:08:54.700 --> 00:08:57.600
or are larger
than need to be presented.

00:08:57.600 --> 00:08:59.700
Stacking the cards
with the grating face down

00:08:59.700 --> 00:09:01.733
keeps the examiner unaware
of the position

00:09:01.733 --> 00:09:03.866
of the grading before testing.

00:09:03.866 --> 00:09:07.632
It also minimizes damage
to the grating face of the card.

00:09:07.633 --> 00:09:09.633
Papers can be inserted
between each card

00:09:09.633 --> 00:09:12.666
in order to minimize marks
or blemishes.

00:09:12.666 --> 00:09:15.832
The not-seen stack
has the start card top-most,

00:09:15.833 --> 00:09:17.433
with progressively fine gratings

00:09:17.433 --> 00:09:19.733
in series below the top card.

00:09:19.733 --> 00:09:22.499


00:09:22.500 --> 00:09:24.866
The seen stack
has the gratings that are coarser

00:09:24.866 --> 00:09:25.999
than the start card,

00:09:26.000 --> 00:09:29.600
in a series of progressively
wider stripes below the top card.

00:09:29.600 --> 00:09:31.433


00:09:31.433 --> 00:09:35.133
The examiner picks up the top card
from the not-seen stack,

00:09:35.133 --> 00:09:37.866
and tests the infant
with this grating.

00:09:37.866 --> 00:09:40.232
If she judges the infant
detects the grating,

00:09:40.233 --> 00:09:42.699
she places it on the seen stack.

00:09:42.700 --> 00:09:46.000


00:09:46.000 --> 00:09:49.233
At some point, the series
of judgments will become difficult,

00:09:49.233 --> 00:09:50.566
and the examiner may be unsure

00:09:50.566 --> 00:09:52.866
whether the patient detects
that grating.

00:09:52.866 --> 00:09:54.899
The examiner does not look
at the front of the card

00:09:54.900 --> 00:09:57.266
for this grating location.

00:09:57.266 --> 00:10:00.566
The examiner places the card
the infant does not detect

00:10:00.566 --> 00:10:03.166
on top of the not-seen stack.

00:10:03.166 --> 00:10:05.399


00:10:05.400 --> 00:10:08.733
The examiner then retests
the previously seen grating.

00:10:08.733 --> 00:10:11.033
And if she judges the infant
detects it,

00:10:11.033 --> 00:10:14.333
she places the card on top
of the seen stack again.

00:10:14.333 --> 00:10:15.366
[no audible dialog]

00:10:15.366 --> 00:10:18.299


00:10:18.300 --> 00:10:20.466
If the examiner still cannot determine
that the patient

00:10:20.466 --> 00:10:21.666
detects the grating,

00:10:21.666 --> 00:10:24.732
this indicates that a below-threshold
grating has been found,

00:10:24.733 --> 00:10:26.633
and testing is completed.

00:10:26.633 --> 00:10:28.033
The next-coarser grating,

00:10:28.033 --> 00:10:30.833
the finest the patient
responds positively to,

00:10:30.833 --> 00:10:33.833
is recorded
as the patient's acuity.

00:10:33.833 --> 00:10:36.666
Sometimes, retesting results
in different decisions

00:10:36.666 --> 00:10:38.099
on the patient's detection,

00:10:38.100 --> 00:10:40.966
and the examiner must go back
and forth between several cards

00:10:40.966 --> 00:10:43.166
to determine the patient's acuity.

00:10:43.166 --> 00:10:44.566


00:10:44.566 --> 00:10:45.966
After testing a patient,

00:10:45.966 --> 00:10:49.099
the cards can be placed
in a single stack, ready for storage.

00:10:49.100 --> 00:10:50.133


00:10:50.133 --> 00:10:52.833
We recommend randomly
reordering the right-left locations

00:10:52.833 --> 00:10:55.633
of the gratings to avoid
biasing the grating locations

00:10:55.633 --> 00:10:57.466
to one side.

00:10:57.466 --> 00:11:00.666
As indicated,
the finest or smallest grating size

00:11:00.666 --> 00:11:03.332
that the patient is judged to see
by the examiner

00:11:03.333 --> 00:11:05.999
defines their visual acuity.

00:11:06.000 --> 00:11:08.166
The recording form shown
in the handbook

00:11:08.166 --> 00:11:10.766
can be used to record information
about the patient,

00:11:10.766 --> 00:11:12.399
such as name,

00:11:12.400 --> 00:11:14.000
date of birth,

00:11:14.000 --> 00:11:15.333
test date,

00:11:15.333 --> 00:11:16.999
and age.

00:11:17.000 --> 00:11:19.133
It is also used
to record the important results

00:11:19.133 --> 00:11:20.733
of the acuity test,

00:11:20.733 --> 00:11:24.399
including the acuity card
at threshold in cycles per centimeter,

00:11:24.400 --> 00:11:27.366
test distance, and acuity conversion.

00:11:27.366 --> 00:11:29.166
The examiner can take the value

00:11:29.166 --> 00:11:32.532
from the "Teller Acuity Card Handbook,
Appendix D,"

00:11:32.533 --> 00:11:35.199
showing conversions
from cycles per centimeter

00:11:35.200 --> 00:11:38.933
to cycles per degree, Table 1,

00:11:38.933 --> 00:11:42.333
and from cycles per centimeter
to Snellen equivalents.

00:11:42.333 --> 00:11:46.333


00:11:46.333 --> 00:11:49.233
The patient's acuity can be shown
on an age-norm graph

00:11:49.233 --> 00:11:51.866
from the "Teller Acuity Card
Handbook."

00:11:51.866 --> 00:11:54.866
The patient's age is noted
at the bottom of the graph.

00:11:54.866 --> 00:11:56.732
The test distance is circled,

00:11:56.733 --> 00:11:58.366
and the grating
in cycles per centimeter

00:11:58.366 --> 00:12:02.032
in the column
under the test distance is also circled.

00:12:02.033 --> 00:12:05.699
A line is drawn from this value
across to the patient's age.

00:12:05.700 --> 00:12:07.266
This shows
where the patient's acuity

00:12:07.266 --> 00:12:10.799
falls relative to the normal range
for that age.

00:12:10.800 --> 00:12:12.300
All values are then recorded

00:12:12.300 --> 00:12:15.000
in the results section
of the recording form.