Retinal Image Quality II

Question 1

In order to resolve fine details of the pattern imaged on the retina

Answer 1

The adjacent ‘receptor units’ must be sufficiently close together to correctly interpret the pattern

Question 2

Pattern and the receptors are close enough to correctly interpret the pattern

Answer 2

Veridical

Question 3

The visual system is just bale to resolve the pattern

Answer 3

Nyquist limit

Question 4

The sampling rate of the receptor units are inadequate to correctly interpret the pattern. The visual system may perceive the under sampled pattern as much lower spatial frequency and different orientation

Answer 4

Aliasing

Question 5

When the visual system correctly interprets the spatial frequency and orientation of pattern

Answer 5

Veridical system

Question 6

The spatial frequency at which finest light pattern that can be correctly resolved by the retina

Answer 6

Nyquist limit

Question 7

What is the nyquist limit in humans

Answer 7

60c/deg

Question 8

The spatial frequency at whihc the visual system cannot distinguish between light patterns

Answer 8

Aliasing

Question 9

Photoreceptor spacing limits resolution, true or false

Answer 9

False, loses resolution due to there being less ganglion cells for each photoreceptor

Question 10

What is visual resolution limited by

Answer 10

The spacing of (beta) ganglion cells of the retina

Question 11

Why is it the ganglion cells that limit the visual resolution

Answer 11

At fovea, there is a one to one correspondence between cones and ganglion cells.

Question 12

Why is it that cone spacing is not a the limiting factor for visual resolution

Answer 12

Peripheral cones are spaced too closely to be a limiting factor for visual resolution

Question 13

What is the correspondeance of ganglion to PR cells at 0 degrees (fovea)

Answer 13

1:3

Question 14

Where is the correspondence 1:1

Answer 14

5-10 degrees outside the retina

Question 15

Why does the resolution get poorer out in the periphery of the retina

Answer 15

Because fewer ganglion cells

Question 16

Resolution/contrast cannot be better than 60cyl/degree, true or false

Answer 16

True-if optics + neural blur is taken into consideration

False-if only considering neural blur

Question 17

What is the difference in contrast sensitivity between normal eye (optics + neural blur) and an eye that has no optics

Answer 17

10x difference

Question 18

What could the nyquist limit be if we could bypass the optics

Answer 18

With laser interometry, the contrast sensitivity of the human eye could be increased from spatial frequency of 60cycl/deg to 120 c/deg

Question 19

What limits the ability to resolve higher spatial frequency ?

Answer 19

Optics

Question 20

When frequency increases, what happens to grating spacing

Answer 20

Decreases

Question 21

What happens to MTF with increased frequency

Answer 21

Decreased

Question 22

What is the difference between monofocal and multifocal lenses in terms of MTF

Answer 22

Monofocal is close to ideal at 0.75 and multifocal is about 0.3, so multifocal have poorer image quality

Question 23

Resolves both SPATIAL FREQUCNY and ORIENTATION

Answer 23

Veridical

Question 24

How do we get to 120 nyquist limit

Answer 24

Get rid of optics

Question 25

What are the two major spatial tasks performed by human system

Answer 25

Resolution and detection

Question 26

What do cones limit

Answer 26

Detection

Question 27

Ability of the patient to detect that a spot of light is present. Details not impiotant

Answer 27

Detection

Question 28

Half period of the finest detectable grating

Answer 28

Minimum angle of detection (MAD)

Question 29

The detection in the central and peripheral vision is limited by the size of the

Answer 29

Cone photoreceptors

Question 30

What is resolution limited by

Answer 30

Ganglion cells

Question 31

Resolution and detection at the fovea

Answer 31

Patterns may be reliable resolved anad detected

Question 32

Resolution and detection in the periphery

Answer 32

Can detect, cannot resolve

Question 33

Difference between ability to detect and resolve in the periphery

Answer 33

Aliasing

Question 34

Where is detection and resolution pretty much matched

Answer 34

Fovea

Question 35

What are the 3 components of the recognition pyramid

Answer 35

1. Detection 2. Resolve elements 3. Identification

Question 36

Discriminating optical and neural blur

Answer 36

May help in distinguishing between diseases and in establishing a course of treatment

Question 37

Central vision retinal image

Answer 37

Considerable variation

Question 38

When is there an over estimation of retinal image quality

Answer 38

When scattering effect being ignored

Question 39

The most important optical defect affecting retinal image quality is

Answer 39

Defocus

Question 40

What are the main things that affect optic blur

Answer 40

Diffraction Aberration Scatter Defocus

Question 41

Why is it important to correct even the smallest refractive error

Answer 41

To prevent incorrect attribution of losses to retinal/neural pathological causes

Question 42

TCA causes _____ much loss of resolution for 3mm displacement of small aperture

Answer 42

3 times

Question 43

What is the anchoring role

Answer 43

Stiles crawford effect

Question 44

What si the stiles crawford effect

Answer 44

Max intensity of light in the center of the pupil compared to the periphery, this helps reduce aberrations entering the eye

Question 45

Pupil decentration on retinal IQ

Answer 45

Decentration of the eyes pupil induces additional optical aberrations such as transverse chromatic aberration and coma, which decrease spatial visual performance This is either temporally or nasally.

Question 46

What is peripheral vision important for

Answer 46

Detection, not resolution

Question 47

Improving peripheral vision

Answer 47

Has little improvement in resolution but marked improvement in detection occurs