Perceptual Function/Color Vision

Question 1

At which age do children begin to distinguish between different colored stimuli?

Answer 1

3 months

Question 2

Information received by the PRs of the retina from the ganglions cells is an example of what type of pathway?

Answer 2

The centrifugal pathway

-feedback loop

Question 3

What is the centripital pathway?

Answer 3

Info tranmitting from PRs to bipolar cells to ganglion cells in a forward fashion

Question 4

Amacrine and horizontal cells are responsible for what?

Answer 4

Lateral integration of data

Question 5

Scotopic vision is mediated primarily by which type of receptor in the retina?

Answer 5

Rods

Question 6

How much light is needed to trigger a single molecule of rhodopsin?

Answer 6

1 quanta

Question 7

What is Weber’s law?

Answer 7

Law that states that as the background brightness is increased, the increment threshold of the test stimulus must also increase, such that the ratio of the incrememnt intensity to the background intensity remains the same

Question 8

The scotopic system posesses (good/poor) spatial summation.

Answer 8

Good spatial summation

Question 9

What colors are the background and target of short wavelength perimetry?

Answer 9

Blue stimulus

Yellow background

Question 10

Which photoreceptors may be more susceptible to early glaucoma damage, thus making the use of SWAP potentially important?

Answer 10

S-cones

Question 11

What type of contact lens would benefit a dichromat?

Answer 11

X-Chrome

Question 12

Is the X-Chrome lens worn in one eye, or both eyes?

Answer 12

One eye

Question 13

Peak PR sensitivity occurs when light passes through which part of the pupil as it enters the eye?

Answer 13

Slightly nasal to the center of the pupil

-PR inner and outer segments act as optic fibers with TIR, directing all the light inward

Question 14

How is it that a monovision patient can report good retained depth perception?

Answer 14

Monocular depth cues

Question 15

Name 3 things that could cause a false superior field defect on HVF.

Answer 15

Deep set eyes and large brow ridge
Trial lens set too low
Pt with head tilted back

Question 16

The change in peak spectral sensitivity from higher wavelengths to lower wavelengths as the surrounding illumination decreases is the basis for which theory?

Answer 16

Purkinje shift

-As illumination increases, we shift from scotopic to photopic

Question 17

Color vision tests are best administered under which type of illumination?

Answer 17

A MacBeth lamp

Question 18

Which type of visual acuity is most affected by defocus?

Answer 18

Resolution acuity

Question 19

Ricco’s law holds only for stimuli that are below a critical ___.

Answer 19

Diameter

Question 20

What is the critical diameter in Ricco’s law?

Answer 20

10’ arc

Question 21

Weber’s law deals with what?

Answer 21

Just noticeable difference

Question 22

Bloch’s law applies to what?

Answer 22

Temporal summation

Question 23

UV coating on lenses act as what type of filter?

Answer 23

Long-pass filter

Question 24

What do long-pass filters absorb?

Answer 24

Short wavelengths

- let the long wavelengths pass

Question 25

How are broad-band and narrow-band filters similar?

Answer 25

They only transmit wavelengths within a certain selected range

Question 26

Brodmann's area 17 is part of what?

Answer 26

Primary visual cortex

Question 27

The primary visual cortex is also known as what?

Answer 27

Striate cortex

Question 28

Where does the striate cortex send its projections?

Answer 28

Extrastriate cortex, consisting of: IT, MT, V2, V4, V5

Question 29

Illuminance is directly related to what?

Answer 29

The total amount of lumens emitted from a source | -total illuminance doesn't depend on any properties of the surface, only the source

Question 30

A sign that gives the illusion of a person drinking a soda through the use of apparent motion caused by flashing lights it an example of what?

Answer 30

Phi phenomenon

Question 31

Phi phenomenon is also known as what?

Answer 31

Stroboscopic motion

Question 32

What are Mach bands?

Answer 32

Perceived bands within transitions zones of a smooth transition between gray/white/to black

Question 33

What causes Mach bands?

Answer 33

Visual system, due to the augmentation of high spatial frequencies

Question 34

A typical human contrast sensitivity function is a band-pass function with a peak of how many cycles per degree?

Answer 34

4 cycles/degree

Question 35

While performing a VF using FDT, what correction should be worn by the pt?

Answer 35

Distance correction | -FDT simulates optical infinity

Question 36

What makes up a cortical hypercolumn?

Answer 36

Ocular dominance columns for both eyes, and a complete set of orientation columns

Question 37

A person missing the chlorolabe photopigment is called what?

Answer 37

A deuteranope

Question 38

A tritanope is missing which photopigment?

Answer 38

Cyanolabe

Question 39

A person missing erythrolabe is considered what?

Answer 39

Protanope

Question 40

What is the difference between dichromacy and anomalous trichromacy?

Answer 40

In anomalous trichromacy, the person has all three types of cones, but one doesn't function correctly. Dichromats are mission a cone type

Question 41

In the signal detection theory, what occurs as the detectability of the stimulus is increased?

Answer 41

There is less overlap between the signal and the signal plus noise curves

Question 42

Spatial summation of the scotopic system follows Ricco's law, so long as the test spot is not greater than 10' arc. What is the relationship between stimulus intensity and stimulus area according to Ricco's law?

Answer 42

Within the critical diameter, as the stimulus intensity increases, the stimulus area decreases

Question 43

What is the formula for Ricco's law?

Answer 43

IA=K I = stimulus intensity A = stimulus area K = Constant

Question 44

What is the Stiles-Crawford effect?

Answer 44

Rods and cones respond differently to incident light that is not perpendicular to their surface

Question 45

According to the Stiles-Crawford effect, light that strikes cones perpendicularly to their surface will have (maximal/minimal) absorption.

Answer 45

Maximal | -will be reported as brighter

Question 46

The Stiles-Crawford effect is not noted with which system (Photopic/Scotopic)?

Answer 46

Scotopic

Question 47

What is the contrast of a projected VA chart in which the target luminance is measured as 50 units of light, and the background luminance measures 100 units of light?

Answer 47

33% -(target luminance - background luminance)/(target luminance +background luminance) = (50-100)/(50+100) = 33

Question 48

Which color vision test is able to differentiate between a dichromat and an anomalous trichromat?

Answer 48

Anomaloscope

Question 49

What is the most likely reason that a patient is able to retain good VA despite the fact that they are missing a photopigment (anomalous trichromacy)?

Answer 49

The missing photopigment is replaced by the remaining photopigments that are present

Question 50

As applied to color vision, what is the proper term for two stimuli that appear the same, but are physically different?

Answer 50

Metamers

Question 51

A patient with a cvisual acuity of 20/30 will likely display a high spatial frequency cut-off of how many cycles per degree?

Answer 51

20 cycles per degree

Question 52

How do you convert from Snellen to cycles per degree?

Answer 52

Divide 600 by the Snellen denominator | Ex: 20/30 = 600/30 = 20

Question 53

A person can just detect the difference between two weights: one 12 lbs, and the other 10 lbs. What is the JND for 70 lbs?

Answer 53

14 lbs

Question 54

What 3 things can be determined from a CIE diagram?

Answer 54

Excitation purity of a stimulus Dominant wavelength of a stimulus Complimentary colors

Question 55

Which form of VA possesses the smallest threshold?

Answer 55

Detection acuity

Question 56

What is detection acuity?

Answer 56

The ability to determine presence or absence of a target in an empty field

Question 57

What is the threshold of detection acuity?

Answer 57

1 second of arc

Question 58

The fact that 100 quanta of 507nm and 200 quanta of 580nm produce the same effect on rhodopsin is known as which of the following?

Answer 58

The principal of univariance

Question 59

What is the Purkinje shift?

Answer 59

The shift in peak spectral sensitivities during the change from scotopic to photopic vision -as lighting increases, longer wavelengths appear brighter because the peak spectral sensitivity for scotopic conditions is 507nm, and 555 nm for photopic

Question 60

A piece of paper is held 2 feet away from a point source of light with an intensity of 60 candelas. What is the resultant illumination on the surface of the paper?

Answer 60

15 candelas | -The illumination of a surface will decrease by the square of the distance

Question 61

What is the unit for luminous power?

Answer 61

Lumens

Question 62

Which filter essentially transmits a single wavelength of light?

Answer 62

Interference filter

Question 63

Which term is used for the event where an observer correctly reports the lack of stimulus on a threshold test

Answer 63

Correct reject

Question 64

An observer is presented with left-tilted bars seen exclusively by the left eye, and bars that are tilted to the right viewed only by the right eye. The observer reports seeing alternating images of the right and left tilted bars, but the images do not fuse. What phenomenon explains this?

Answer 64

Binocular rivalry

Question 65

You measure a patients contrast sensitivity. She is able to correctly identify 20/20 with a 1 percent contrast. What is her contrast sensitivity?

Answer 65

100 | - take the reciprocal of the contrast threshold

Question 66

Snellen is a type of which acuity?

Answer 66

Resolution

Question 67

The scotopic system is more sensitive than the photopic system for all wavelengths except those of which color?

Answer 67

Red

Question 68

What is the photochromatic interval?

Answer 68

Measure of the difference in sensitivities between the photopic and scotopic system for a given wavelength

Question 69

The photopic system is more sensitive than the scotopic system for wavelengths greater than what?

Answer 69

650nm

Question 70

How is the human contrast sensitivity function expected to change for a myope who is uncorrected?

Answer 70

The high spatial frequency cut-off will shift to a lower frequency -high spatial frequency most affected without correction

Question 71

During a saccadic movement, which pathway is suppressed?

Answer 71

Magno | -During a saccade, vision is suppressed just before, during, and just after the motion

Question 72

When looking at an image depicting light gray on sone side, black on the other, and a smooth transition in between, observers report the appearance of light and dark bars. What is the name of this phenomenon?

Answer 72

Mach Bands

Question 73

What is the high-spatial frequency cut-off for a young adult free of ocular pathology?

Answer 73

60 cycles per degree (20/10) | -limited by anatomy

Question 74

A typical human contrast sensitivity function is a band-pass function with a peak of how many cycles per degree?

Answer 74

4 cycles per degree