Resolution and Acuity

Question 1

Define Spatial Acuity ?

Answer 1

The smallest spatial detail can be detected, resolved or identified

Question 2

What types of Spatial acuity are there?

Answer 2

Detection acuity
Hyperacuity
Resolution acuity
Identification Acuity

Question 3

What is detection acuity ?

Answer 3

Angular size of the smallest spot or width of line that can just be detected
is it there or is it not (2AFC)

Question 4

What are small objects detection depend on?

Answer 4

Illuminance of the retinal image and not size

increment threshold delta L/L

Question 5

What is retinal image size limited for small objects?

Answer 5

differaction and abberation

Question 6

What is increment threshold?

Answer 6

The ability to detect if one stimulus intensity differs from another

Question 7

What is increment threshold dependent on?

Answer 7

Stimulus size, duration wavelength, and retinal location

Question 8

What is detection acuity of spot?

Answer 8

0.25-0.33’ arc

Question 9

What is detection acuity of a line ?

Answer 9

0.0083-0.017’ arc

Question 10

What happens to retinal luminance as object gets smaller ?

Answer 10

Retinal luminance decreases

Question 11

How can you detect really small spots/lines?

Answer 11

If they are sufficientyly intense

Question 12

Define hyperacuity?

Answer 12

Smallest spatial offset or difference in location that can be resolved

Question 13

Give examples of hyperacuity?

Answer 13

Displacement
vernier
tilt
stereoacuity

Question 14

What is displacement hyperacuity?

Answer 14

Relative location or displacement of dots or lines

Question 15

What is vernier acuity?

Answer 15

Smallest spatial offset or difference in location that can be resolved

Question 16

What is tilt?

Answer 16

Smallest spatial difference in location that can be resolved

Question 17

What is stereoacuity ?

Answer 17

Smallest spatial difference in location that can be resolved

Question 18

What are results of Hyperacuity?

Answer 18

Under opimum condition with high contrast stimuli 2-6’ arc

Question 19

When is hyperacuity suggested to be used?

Answer 19

Media opacities to test neural function- cataract

Question 20

What is resolution acuity?

Answer 20

Smallest separation of two points or lines that can be discriminated

Question 21

What condition does resolution acuity need to be in?

Answer 21

Under optimum conditions 0,5’ arc

Question 22

How is it hard to do resolution acuity>?

Answer 22

> need lines of different size, and thickness otehrwise px will know
high luminance causes smaller pupil size more deffraction
astigmatism repeat test on all orientation with lines

Question 23

What does high luminance cause?

Answer 23

Smaller pupil size
diffraction
reduced resolution

Question 24

How does grating resolve problems?

Answer 24

Highest spatial frequency gratings (thin) that subject can detect

Question 25

What is gratings not good for?

Answer 25

Testing resolution acuity

Question 26

What is the advantages of identification acuity?

Answer 26

Highly familiar and easily identified targets
quick and reliable
sensitive to ametropia
less effected by guessing

Question 27

What is high contrast?

Answer 27

Allows for variation in the stimulus or lighting without affecting results significantly

Question 28

What confidence intervals do test have?

Answer 28

95% and VA wil fall within +/- 1 line