9- Spatial Vision

Question 1

What is spatial vision concerned with?

Answer 1

Variations in luminance across space

Question 2

What are the 2 characteristics of sine-wave grating

Answer 2

Frequency and contrast

Question 3

Low spatial frequency grating looks like

Answer 3

Bars more spread out

Question 4

High spatial frequency bars look like

Answer 4

Closer together

Question 5

Lower contrast bars

Answer 5

Dimmer, paler

Question 6

High contrast bars appear

Answer 6

Darker

Question 7

A lens is used to form an image of a sine wave grating. What does the spatial frequency depend on?

Answer 7

Magnification of the lens

Question 8

A lens is used to form an image of a sine-wave grating. What affects modulation depth

Answer 8

The quality of the lens

Question 9

For a real lens, as spatial frequencyof the object becomes greater, what happens to the amplitude?

Answer 9

Gets smaller

Question 10

What is resolution

Answer 10

An imaging systems ability to distinguish object detail

Question 11

What is contrast

Answer 11

How faithfully the min and max intensity values are transferred from object to image plane

Question 12

OTF:

Answer 12

MTF+ PTF

Question 13

What does the MTF measure

Answer 13

The lens ability to transfer contrast at a articulate resolution from the object to image

Question 14

As line spacing decreases what affect does that have on the lenses ability to transfer the contrast?

Answer 14

More difficult

MTF decreases

Question 15

In an on axis optical system is there any change in phase with spatial frequency?

Answer 15

No

Question 16

At low-moderate spatial frequencies do aberration have an affect?

Answer 16

Not as big as in high frequencies

Question 17

What is the effect of optical defocus on SMTF?

Answer 17

Defocus results in a reduction in image quality at high frequencies

Question 18

What is the effect of translucent optics on SMTF?

Answer 18

Overall reduction in overall reduction in image contrast at ALL frequencies
The image formed by the lens is highly degraded

Question 19

For higher levels of defocus what happens to MTF

Answer 19

Decreases the then becomes negative

Question 20

What happens to the image pattern with MTF is negative

Answer 20

Reversed contrast

Question 21

What is the resolution limit

Answer 21

Spatial frequency at which the modulation transfer function first goes to 0

Question 22

What is spurious resolution

Answer 22

Any resolution of higher frequency pattern

Question 23

Point where the grating is first seen by the patient

Answer 23

Contrast threshold

Question 24

What is the reciprocal of contrast threshold

Answer 24

Contrast sensitivity

Question 25

What is the maximum sensitivity

Answer 25

4 cpd

Question 26

What is the high frequency cut off

Answer 26

The point where the grating can no longer be resolved

Question 27

What is the approximate high frequency cutoff?

Answer 27

60 cpd

Question 28

How does the high frequency cut off relate to VA

Answer 28

It is the point where the details of the optotypes can no longer be resolved

Question 29

What is the optical limitation of high frequencies

Answer 29

Manifests a high frequency limitation because of optical aberrations

Question 30

What does the packing of retinal photoreceptor have to do with high frequency

Answer 30

A finer matrix is able to resolve better

Question 31

What happens to high frequency cut off in uncorrected refractive errors

Answer 31

There is reduction in the high-frequency cutoff that manifests itself as decreases VA

Question 32

How does the high frequency CSF cutoff relate to snellen acuity

Answer 32

It’s the angle that just resolvable bars make with the eye is called minimum angle of resolution