Below a gothic tower a boy navigates with a cane.

A title: Visual Acuity Testing:

Acuity Cards and Testing Procedures

with D. Luisa Mayer, Ph.D.

- About in the '80s, people were really interested

in using various techniques, electrophysiology

but of course behavior, to measure visual functions

in babies that had visual problems.

And particularly to measure visual acuity,

which is the most important, probably,

most important visual function that you can measure

in an individual with a visual impairment.

And there were a number of different researchers

who were interested in this and in doing this,

modifying procedures and so forth.

And at that time, in the '80s,

I had finished my dissertation,

my OPL research, and came to Children's Hospital in Boston

to work with Anne Fulton, who was the first ophthalmologist

to bring FPL into a clinical setting.

And she did that with Velma Dobson's collaboration.

They brought an apparatus, which I help set up

at Children's Hospital in Boston in '79, I believe.

And they did some feasibility studies

and showed that you could actually use it

to test babies using shortcut procedures.

You couldn't do full psychometric functions

with babies in a clinic because you can't spend days

testing their vision.

But you could do it with shortcut procedures.

Teller was having troubles about our using FPL and OPL.

I brought OPL to Children's Hospital

and we're able to test most kids with that.

Not everybody, but a lot of kids.

But she felt there were problems with bringing FPL and OPL

into the clinic and using it to test babies.

And she felt that there really needed to be

a real clinical test of visual acuity

that could be applied in all kinds of clinical settings.

And she did something quite shocking to those of us

who worked with her because she went against

her psychophysics and against the scientific basis

of FPL and OPL.

And she did away with it.

And she said there's a lot of information that observer

is getting from the baby that doesn't get conveyed,

it doesn't get used in forced choice preferential looking.

For example, those very strong looks to big stripes

and the subtler looks to smaller stripes

and the subtle things that babies do,

because sometimes they raise their eyebrows

when they see stripes, and maybe that's a strong cue

that, yeah, they really saw and were interested in the stripes.

She felt that subtle, more subjective information

could be translated into a test where the observer

now controlled the testing.

And how did they do that?

She had the stripes mounted on gray cardboard

where the stripes were in one position

and that gray stimulus was still over there

and it was a gray surround and a gray card.

So the stimulus was the same, but the stripes

were on individual cards.

Every card had a different sized stripe.

And the observer was to use those cards

in whatever way they needed to, to find out if the baby

detected the stripes.

No longer was she saying the stripes were on

the right or the left.

NARRATOR: A photograph shows Davida Teller

with a number of rectangular cards fanned out

in front of her.

The width of the stripe stimulus varies from card to card.

- Well, we were really upset because we felt

that put too much control into the hands of the observer,

who could be biased.

We were observers, after all.

And as somebody looking at a little baby,

you want them to have 20/20 vision.

So you're going to say we felt that baby sees that card,

of course.

And Teller said, "Well, yes, there is the problem of bias,

"but the procedure can be designed so that

you minimize bias."

And how do you do that?

You keep the person showing the stripes ignorant or unaware

of where the stripes are until the person finishes testing.

Test this stripe multiple times showing it to the right

and the left, making sure that they think the baby sees it

because the baby looks strongly that way, flip the card,

the baby looks strongly this way, flip it again.

The baby looks strongly that way.

"I really think the stripes are there."

Check, "Oh, I was right."

And that kind of information the observer could

keep themselves objective to a certain point,

then confirm their judgment,

so give themselves feedback about it.

The corollary of that is that if you didn't think

the baby saw the stripes or you weren't sure,

you didn't check the front because you could

really be biased by that.

There are only two choices, after all.

So 50% of the time you could guess it correctly

and the baby's not seeing it.

So those two controls really, really answered

the question about controlling for observer bias,

at least to some degree.

The first iteration of this was to present these cards

in an apparatus very much like

the forced choice preferential looking apparatus,

but a portable one that could be put on a table.

And we called it a stage because it turns out

it looked sort of like a puppet stage.

And it had a rectangular window in the middle,

behind which the cards could be presented

and moved away and then flipped and presented again.

And so that made it very convenient

and made it pretty easy, easy to fit on a table

in some room.

You could close it up, it was portable,

you could put it away.

One really wonderful thing that happened was that window.

Because now that window opened the observer's view

and the baby's view of the observer

and also to a puppet show.

So often we would hold up a little puppet

to keep the baby's interest or sometimes our face

looking at them was enough to look through that window.

And then the card would go up and the baby

would still be looking,

sometimes waiting for you to show up again,

so you had to be a little careful

about how animated you were.

That's one of my problems is I would sit there

and play with the babies, but not do my test.

NARRATOR: We see a video clip of Luisa Mayer

administering an acuity card test to a young boy.

The boy sits on his mother's lap in front of the stage

as the cards are presented to him in the window.

When the cards are removed from the window and rotated,

the observer is able to engage the child's attention

before presenting the card again in a new orientation.

The child is observed through a peephole

in the middle of each acuity card.

- But that was a great, really clinically important thing

that happened just by chance, essentially.

It wasn't planned, so it was really, really nice.

So essentially the acuity card procedure--

which is what it was called-- wasn't very much different

in terms of the stimulus and the presentation mode

and the observer's task, in a sense, from FPL,

except that all of the psychophysics

and all of the counting and percent correct

and statistics that were done didn't need to be done.

In the '80s, Teller and Dobson and their colleagues

in Seattle did a number of studies of the ACP,

the acuity card procedure,

essentially to show how or to find out

how did it compare with FPL and OPL,

and it turns out the norms are very close.

They agree rather well.

And in a direct comparison between FPL

and the acuity card procedure in babies with visual problems,

it turned out they agreed remarkably well.

These were monocular tests,

you know, babies being tested one eye at a time.

They also discovered that test re-test reliability

was pretty good, which is very important.

You need to know you're going to get about the same answer.

Well, it isn't about the same, it can vary over a range,

but they found that out.

The other thing that was very useful

was they did a study of feasibility,

that is how does this work?

How does the acuity card procedure work

in clinical settings?

And they went to ten diverse clinical settings,

one of them being Children's Hospital, where I was,

struggling away doing OPL with babies.

And so we started using it at Children's Hospital,

and a number of other people did.

And we found it was a great test.

It was a fabulous clinical test.

We could test really rapidly, we could get a measure

in each eye of a baby in ten minutes or less.

Whereas it would take 30 to 40 minutes--

well, sometimes 20 minutes in a really good baby--

to do OPL thresholds with them.

The equipment was easier to handle,

there wasn't all that calibration of stripes

that I had to do.

It was just altogether good.

There were a lot of babies we could test now

that we hadn't been able to, so it was wonderful.

We loved it.

And we weren't the only ones.

NARRATOR: Fade to black.

A graphic of the Perkins logo swoops across the screen,

revealing a chapter heading:

Modification of Acuity Card Procedure.

- The thing that we discovered at Children's Hospital

when we started using acuity cards was that we didn't...

we could test more easily without the stage.

We could present the cards now in the baby's position,

in wherever we needed to present it for them

to see them as easy as possible.

And for us to make their observations

as easy as possible too.

NARRATOR: In this photo, Davida Teller is on the left

holding her grandson while the baby is being shown

a Teller acuity card by his father,

Davida's son, on the right.

He holds the card horizontally, the standard way

of presenting acuity cards.

Note how strongly the baby gazes at the grating.

In a series of two photos, we see a young boy being held

in his mother's lap while an acuity card

is presented to him.

The card is being presented in a vertical

rather than the usual horizontal orientation.

- For children who have very low vision,

who if you hold something at too far a distance

they can't see it very well,

we can get quite close and we can show the stripes

right to their face, very close.

And we can observe their behavior.

So taking the cards out of the apparatus

was another revelation.

So the first revelation was that

operant preferential looking apparatus could be

put in the closet, and the second was the stage

could be put in the closet.

And that freed up really precious clinical space,

which has gotten even worse as years go on

and as more things are being done in clinical spaces.

So now the cards are just set on a table,

they're available to me whenever I want to pick them up

and show them to a baby.

I don't have to do anything fancy,

I just store them carefully with a cloth over them and so forth.

NARRATOR: In a video clip, we see a demonstration

of an acuity card test being administered

to a very young boy.

The boy is in his mother's lap as she sits in a chair