Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

OT > Visual Resolution > Flashcards

Visual Resolution Flashcards

1
Q

What is the Snellen Fraction?

A

Test Distance/ Distance at which the letter subtends 5 minutes (5/60*) of arc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does VA 20/40 mean?

A

The smallest letter the pt could read subtended 5 minutes of an arc at 40 feet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is recognition acuity?

A

Snellen Chart
Must be able to see and name the letters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is detection acuity?

A

The direction the child moves it eyes to the area with more stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is resolution acuity?

A

The direction the letter points

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is localization acuity?

A

What is the smallest gap between the lines that a patient can resolve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is vernier acuity?

A

The smallest angle between lines that a pt can resolve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do you find the height of a 20/200 letter?

A

20/200 letter subtends 5 mins of arc at 200ft thus half the letter subtends 2.5 mins at 200 ft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How much does a 20/100 letter subtend at 20ft?

A

20/100 subtends 5’ at 100ft thus at 20ft it would subtend 5 x5= 25’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How much does a 20/15 letter subtend at 20ft?

A

20/15 subtends 5’ at 15ft thus at 20ft it would subtend 5 x(15/20)= 3.75’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens when you halve or double the viewing distance?

A

When you halve the viewing distance the angular subtense doubles.

When you double the viewing distance the angular subtense halves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does vernier acuity give you?

A

Vernier acuity displays the smallest angle between the lines that the patient can resolve thus you must solve for the angle theta= Tan(x)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Can you average snellen VA?

A

NO you can only average MAR

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is MAR?

A

The minimum angle of resolution which is the angle that must be resolved for the patient to be able to identify the letter correctly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does each limb of a letter subtend?

A

Snellen letters are made on 5x5 thus each limb subtends 1’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does a 5x4 non serif subtend?

A

Each limb is still only 1’ because it is on 5x5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do you calculate MAR?

A

Denominator/ Numerator ie: 20/100= 100/20= MAR=5
logMAR= 1.0

17
Q

What does each limb of a 20/40 letter subtend at 20ft?

A

Each limb would subtend 2’ each thus at 20ft it is 5x2= 10 minutes

18
Q

What is the space between each letter on a logMAR chart equal to?

A

The width of a letter

19
Q

How much is each letter on a logMAR chart worth?

A

0.02

20
Q

Is logMAR 20/20= 0.0 good?

A

No, 75yo can see this.

21
Q

What is the decimal equivalent of 20/100 letter?

A

0.2 (Numerator/ Denominator)

22
Q

If the patient can’t read the letters what is the order of tests your perform?

A
  1. Hand motion
  2. Light Projection
  3. Light perception
  4. No light perception
23
Q

What is near VA performed at?

A

16in or 40cm

24
Q

What is near Jaeger?

A

Letter ranging from J1- J20 but they are not standardized size

25
Q

What is M notation?

A

M denotes the distance in meters which the letter subtend 5’. M= denominator of a Snellen fraction (in meters)

26
Q

If the smallest print a pt can read is 0.5M what is their VA at 40 cm?

A

0.4/0.5

27
Q

What is N notion?

A

Used for near VA.
One point= 1/72 of an inch. The smallest size is N5 or 5/72.

28
Q

What does point size refer to?

A

It refers to the size of the block the letter is on. Ie: 10 point means the block was 10/72 in high.

29
Q

How big are lower case letters with or without ascenders considered to be?

A

5/72in. high

30
Q

Which factors affect VA?

A

Blur
Contrast
Retinal Eccentricity

31
Q

What happens if blur circles are overlapping?

A

The patient will be unable to resolve a letter

32
Q

What does a pinhole od?

A

It reduces the diameter of the blur circle. It does not change where the light focuses thus the eye still has the same refractive power

33
Q

What is the contrast equation?

A

Lmax-Lmin/ Lmax + Lmin

34
Q

At which point in contrast does VA change?

A

Less about 40% contrast do we see a drop off in VA

35
Q

What is retinal eccentricity?

A

Retinal eccentricity describes how far a point on the retina lies away from the fovea (center of macula)

36
Q

How is retinal eccentricity expressed?

A

It is expressed as an angle. In this picture point X lives alpha degrees away from the fovea.

37
Q

What is the VA for retinal eccentricity on the fovea?

A

20/20

38
Q

What is the VA for retinal eccentricity on 1 degree off the fovea?

A

20/30

39
Q

What is the VA for retinal eccentricity 1.5-2 degrees off the fovea?

A

20/40

40
Q

What is the VA for retinal eccentricity 3-5 degrees off the fovea?

A

20/60

41
Q
A

OT (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions