Testing & Administrating Teller Acuity Cards - PV

Teller Acuity Cards
are used to test visual acuity

in young children
and those with disabilities

who cannot be tested
with standard letter

or symbol acuity tests.

The stimulus
on a Teller Acuity Card

is a high contrast black
and white pattern

of stripes called a grating.

The gratings range
from very coarse to very fine,

in order to test visual acuity

from very low vision to normal.

Most rectangular cards
have a single grating

printed off to one side
of the center.

Printing the grating
to one side of the card

allows it to be presented either
on the left

or the right.

An additional card

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

This card
is called the low vision card.

The final card is a blank, gray card
without a grating.

Grating values are specified

by the width
of their black and white bars.

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

Grating sizes are specified

by the number of black
and white cycles per centimeter.

The metric cycles per centimeter

is converted to visual acuity based
on the distance

of the Teller Acuity Card grating
from the patient,

and is specified as cycles
per degree.

The cycles per degree measure
is the appropriate specification

for grating acuity.

If necessary,
grating acuity can be converted

into conventional Snellen notation,

which may be more appropriate
for certain reporting.

Each Teller Acuity Card
has labels on the back

showing the grating size
in cycles per centimeter,

and the conversions to acuity based
on three test distances.

The labels on the back
of the card are placed

so the examiner has no information

about the right-left position
of the grating

from viewing the back of the card.

The primary principle
of a Teller Acuity Card

is that if a patient sees a grating
on the grey background,

she will look at the grating.

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

the grating should match
the grey background perfectly,

mimicking the blank card.

The examiner's task
in testing Teller Acuity Cards

is to determine the finest grating

that the patient sees or detects.

This gives the patient's
visual acuity.

This requires testing a series
of gratings,

starting from relatively wide
and easily seen

to progressively finer gratings,

until the patient
no longer responds consistently.

The recommended clinical method
of testing is

for the examiner
to present a single grating

a sufficient number of times
to judge whether the patient

sees that grating.

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

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

without even watching the patient.

[no audible dialog]

This means that gratings
may need to be shown multiple times

if the patient's responses
are not definitive.

Typically, the patient's responses
will be definitive

when the grating is coarse
and above their acuity level.

However, a finer grating
that is more difficult

for the patient to see
may lead to more subtle responses

and require more presentations.

It is up to the examiner
to determine

how many presentations
she needs to be confident

of the patient's visual acuity.

[no audible dialog]

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

through which the examiner
or tester can view the patient

as they look at the gray card
and the grating.

The examiner can also view
the patient's responses

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

[no audible dialog]

The examiner
is able to change the card position

to judge where the grating
is located, right or left,

based on the patient's
visual behaviors,

such as looking
towards the right or left,

or pointing or other behaviors.

The card is shown to the patient

by an examiner holding it
along the edges.

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

If the examiner uses fingers
to hold the card,

rather than the palm of the hand,

fingertips should not touch
the front,

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

The examiner shows the card
in one position

and makes a judgment as
to where the grating is

based on the patient's behavior.

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

the patient's right.

The examiner
then rotates the card 180 degrees.

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

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

The examiner
should not always rotate the card

180 degrees between presentations,

as some patients
may anticipate the gratings position.

Instead, the examiner
should show the grating frequently

in the same location.

The examiner is being shown
holding the cards

in a horizontal orientation,

which is the standard
and most common way

of presenting Teller Acuity Cards.

However, the cards may be held
in a vertical orientation,

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

This can be a useful method
for testing patients

with nystagmus or strabismus.

During testing,
patients may wish to touch the grating

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

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

and point toward the grating.

To keep the patient's attention,

the examiner can interact with
and reinforce the patient

for finding the grating location.

[no audible dialog]

Presenting a grating that has been
seen previously by the patient

can reestablish interest
in the testing

and also reassure the examiner
that the infant

is still attending
to the gratings.

[no audible dialog]

What behaviors
does the examiner use

to judge whether the patient
sees a grating?

The examiner must be aware of any

and all patient cues and behaviors

that indicate the location
of the grating.

Typically, in young infants,
a strong fixation response

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

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

indicates the infant detects
that grating.

Finer gratings may not be
as strongly fixated,

yet will still elicit a consistent gaze
from the young infant.

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

which are accepted as detection,

because the glance
is direct and clear,

and repeated
on subsequent presentations.

Some mature toddlers
and young children

may point to one side,

especially if prompted by the examiner,
such as,

"Where did the stripes go?"

This section illustrates
the complete sequence

of testing a child's visual acuity
with Teller Acuity Cards.

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

and the parent or holder
should be cautioned

not to give the child any guidance
during testing.

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

Consult the Teller Acuity Card
Reference and Instruction Manual.

If the patient
is visually impaired,

a coarser grating than
that based on age

may be needed for the start card.

Distance of the card
from the patient's face

also depends upon age.

Consult the Teller Acuity Card
Reference and Instruction Manual.

The examiner
measures the test distance

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

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

is an exact measure.

For the 38-centimeter distance,
used with young infants

and patients with limited vision,

a measuring tape can be used.

Or, a convenient measure
is the distance

between the examiner's elbow
and fingers,

with fingers either close or open,

depending
on the examiner's arm length.

This needs to be measured
before testing.

For 84-centimeter distance,

used with older children,
a measuring tape is needed.

Alternatively,
a measuring tape can be placed

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

with marks for each distance.

The examiner should check
the test distance periodically

during the testing,
as some patients will lean forward

to get closer to the gratings,

especially when they
become finer and more difficult to see.

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

on a soft, clean surface.

The card labels are up.

One stack is for gratings
the patient has not seen,

or will not be tested on,

and the other stack is
for cards the patient has seen

or are larger
than need to be presented.

Stacking the cards
with the grating face down

keeps the examiner unaware
of the position

of the grading before testing.

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

Papers can be inserted
between each card

in order to minimize marks
or blemishes.

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

with progressively fine gratings

in series below the top card.

The seen stack
has the gratings that are coarser

than the start card,

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

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

and tests the infant
with this grating.

If she judges the infant
detects the grating,

she places it on the seen stack.

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

and the examiner may be unsure

whether the patient detects
that grating.

The examiner does not look
at the front of the card

for this grating location.

The examiner places the card
the infant does not detect

on top of the not-seen stack.

The examiner then retests
the previously seen grating.

And if she judges the infant
detects it,

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

[no audible dialog]

If the examiner still cannot determine
that the patient

detects the grating,

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

and testing is completed.

The next-coarser grating,

the finest the patient
responds positively to,

is recorded
as the patient's acuity.

Sometimes, retesting results
in different decisions

on the patient's detection,

and the examiner must go back
and forth between several cards

to determine the patient's acuity.

After testing a patient,

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

We recommend randomly
reordering the right-left locations

of the gratings to avoid
biasing the grating locations

to one side.

As indicated,
the finest or smallest grating size

that the patient is judged to see
by the examiner

defines their visual acuity.

The recording form shown
in the handbook

can be used to record information
about the patient,

such as name,

date of birth,

test date,

and age.

It is also used
to record the important results

of the acuity test,

including the acuity card
at threshold in cycles per centimeter,

test distance, and acuity conversion.

The examiner can take the value

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

showing conversions
from cycles per centimeter

to cycles per degree, Table 1,

and from cycles per centimeter
to Snellen equivalents.

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

from the "Teller Acuity Card
Handbook."

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

The test distance is circled,

and the grating
in cycles per centimeter

in the column
under the test distance is also circled.

A line is drawn from this value
across to the patient's age.

This shows
where the patient's acuity

falls relative to the normal range
for that age.

All values are then recorded

in the results section
of the recording form.