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Teller Acuity Cards
are used to test visual acuity

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in young children
and those with disabilities

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who cannot be tested
with standard letter

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or symbol acuity tests.

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The stimulus
on a Teller Acuity Card

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is a high contrast black
and white pattern

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of stripes called a grating.

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The gratings range
from very coarse to very fine,

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in order to test visual acuity

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from very low vision to normal.

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Most rectangular cards
have a single grating

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printed off to one side
of the center.

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Printing the grating
to one side of the card

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allows it to be presented either
on the left

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or the right.

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An additional card

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has a grating nearly covering
one-half of the card.

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This card
is called the low vision card.

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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.

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A single black and white pair
of bars is called a cycle.

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Grating sizes are specified

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by the number of black
and white cycles per centimeter.

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The metric cycles per centimeter

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is converted to visual acuity based
on the distance

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of the Teller Acuity Card grating
from the patient,

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and is specified as cycles
per degree.

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The cycles per degree measure
is the appropriate specification

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for grating acuity.

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If necessary,
grating acuity can be converted

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into conventional Snellen notation,

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which may be more appropriate
for certain reporting.

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Each Teller Acuity Card
has labels on the back

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showing the grating size
in cycles per centimeter,

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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

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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

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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

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to progressively finer gratings,

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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

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if the patient's responses
are not definitive.

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Typically, the patient's responses
will be definitive

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when the grating is coarse
and above their acuity level.

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However, a finer grating
that is more difficult

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for the patient to see
may lead to more subtle responses

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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

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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

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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

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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

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by an examiner holding it
along the edges.

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

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If the examiner uses fingers
to hold the card,

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rather than the palm of the hand,

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fingertips should not touch
the front,

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except possibly within one inch
of the edge of the card.

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The examiner shows the card
in one position

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and makes a judgment as
to where the grating is

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based on the patient's behavior.

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

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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,

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the examiner should judge
the grating is on the infant's left.

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The examiner
should not always rotate the card

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180 degrees between presentations,

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as some patients
may anticipate the gratings position.

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Instead, the examiner
should show the grating frequently

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in the same location.

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The examiner is being shown
holding the cards

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in a horizontal orientation,

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which is the standard
and most common way

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of presenting Teller Acuity Cards.

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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

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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

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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

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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

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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

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to judge whether the patient
sees a grating?

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The examiner must be aware of any

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and all patient cues and behaviors

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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,

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and then to the other side
when the card is rotated 180 degrees,

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indicates the infant detects
that grating.

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Finer gratings may not be
as strongly fixated,

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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,

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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

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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

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not to give the child any guidance
during testing.

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

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Consult the Teller Acuity Card
Reference and Instruction Manual.

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If the patient
is visually impaired,

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a coarser grating than
that based on age

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may be needed for the start card.

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Distance of the card
from the patient's face

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also depends upon age.

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Consult the Teller Acuity Card
Reference and Instruction Manual.

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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

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is an exact measure.

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For the 38-centimeter distance,
used with young infants

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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

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between the examiner's elbow
and fingers,

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with fingers either close or open,

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depending
on the examiner's arm length.

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This needs to be measured
before testing.

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For 84-centimeter distance,

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used with older children,
a measuring tape is needed.

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Alternatively,
a measuring tape can be placed

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on a table surface, adjacent
to the patient and the examiner,

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with marks for each distance.

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The examiner should check
the test distance periodically

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during the testing,
as some patients will lean forward

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to get closer to the gratings,

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especially when they
become finer and more difficult to see.

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

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on a soft, clean surface.

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The card labels are up.

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One stack is for gratings
the patient has not seen,

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or will not be tested on,

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and the other stack is
for cards the patient has seen

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or are larger
than need to be presented.

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Stacking the cards
with the grating face down

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keeps the examiner unaware
of the position

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of the grading before testing.

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It also minimizes damage
to the grating face of the card.

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Papers can be inserted
between each card

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in order to minimize marks
or blemishes.

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The not-seen stack
has the start card top-most,

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with progressively fine gratings

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in series below the top card.

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The seen stack
has the gratings that are coarser

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than the start card,

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in a series of progressively
wider stripes below the top card.

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The examiner picks up the top card
from the not-seen stack,

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and tests the infant
with this grating.

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If she judges the infant
detects the grating,

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she places it on the seen stack.

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At some point, the series
of judgments will become difficult,

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and the examiner may be unsure

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whether the patient detects
that grating.

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The examiner does not look
at the front of the card

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for this grating location.

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The examiner places the card
the infant does not detect

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on top of the not-seen stack.

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The examiner then retests
the previously seen grating.

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And if she judges the infant
detects it,

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she places the card on top
of the seen stack again.

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[no audible dialog]

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If the examiner still cannot determine
that the patient

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detects the grating,

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this indicates that a below-threshold
grating has been found,

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and testing is completed.

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The next-coarser grating,

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the finest the patient
responds positively to,

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is recorded
as the patient's acuity.

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Sometimes, retesting results
in different decisions

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on the patient's detection,

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and the examiner must go back
and forth between several cards

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to determine the patient's acuity.

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After testing a patient,

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the cards can be placed
in a single stack, ready for storage.

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We recommend randomly
reordering the right-left locations

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of the gratings to avoid
biasing the grating locations

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to one side.

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As indicated,
the finest or smallest grating size

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that the patient is judged to see
by the examiner

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defines their visual acuity.

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The recording form shown
in the handbook

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can be used to record information
about the patient,

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such as name,

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date of birth,

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test date,

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and age.

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It is also used
to record the important results

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of the acuity test,

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including the acuity card
at threshold in cycles per centimeter,

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test distance, and acuity conversion.

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The examiner can take the value

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from the "Teller Acuity Card Handbook,
Appendix D,"

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showing conversions
from cycles per centimeter

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to cycles per degree, Table 1,

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and from cycles per centimeter
to Snellen equivalents.

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The patient's acuity can be shown
on an age-norm graph

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from the "Teller Acuity Card
Handbook."

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The patient's age is noted
at the bottom of the graph.

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The test distance is circled,

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and the grating
in cycles per centimeter

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in the column
under the test distance is also circled.

253
00:12:02,033 --> 00:12:05,699
A line is drawn from this value
across to the patient's age.

254
00:12:05,700 --> 00:12:07,266
This shows
where the patient's acuity

255
00:12:07,266 --> 00:12:10,799
falls relative to the normal range
for that age.

256
00:12:10,800 --> 00:12:12,300
All values are then recorded

257
00:12:12,300 --> 00:12:15,000
in the results section
of the recording form.