Visual Perception

Question 1

Person having low threshold …..

Answer 1

Has high sensitivity.

Threshold is inverse of sensitivity

Question 2

Accurate way to determine threshold

Answer 2

Method of constant stimuli
Stairstep method ( Humphery VF)

Question 3

Example of force choice method

Answer 3

Teller acuity card

Question 4

Sensitivity

Answer 4

Probability the test will accurately detect patients with disease
TP/TP+FN

Question 5

Specifity

Answer 5

Probability the test will accurately detect patients without the disease
TN/TN+FP

Question 6

Photometry

Answer 6

Property of light perception .

Question 7

Luminous efficiency function defined as

Answer 7

V=1 brightest V=0 dim
Maximum value 555nm
Fo every watt of power of a light source, the visual system responds with 680 lumens

Question 8

Scotopic lumens

Answer 8

507nm corresponds to 1700 lumens/watt

Question 9

Abney’s law of additivity

Answer 9

Total number of lumens from multiple light source

Question 10

Neutral density filter

Answer 10

Transmit all wavelength equally.

Sunglasses

Question 11

Puff rich phenomenon

Answer 11

Pendulum appears to move in an ellipse rather than back and forth in a plan because of neutral density place on one eye .

Question 12

Scotopic vs photopic

Answer 12

High sensitivity, low sensitivity .

Question 13

Univariance

Answer 13

Photopigments respond to photon absorbed ( quantum) in a manner independent of the wavelength of the photon.

Question 14

Photochromatic intervals

Answer 14

Difference between sensitivity of the Scotopic and photopic system. Zero at 650nm which both are sensitive to this wavelength .

Question 15

Purkinje shift doesn’t exist in

Answer 15

Rods only visual system

Question 16

Sole cause of dark adaptation

Answer 16

Photo pigment regeneration . Dowling-Rushton equation

Question 17

JND

Answer 17

Difference between the intensity of the just perceivable spot of light compared to the intensity of the background .

Question 18

Rocco’s Law

Answer 18

IA=C
If intensity of the stimulus increase, it can still be seen if the area is decreased as log as total number of quanta is constant

Question 19

Bloch’s law

Answer 19

It=C

If duration of flash is increased , the stimulus can still be detected if the intensity of the stimulus is decreased.

Question 20

Stiles-Crawford effect

Answer 20

Cone photoreceptors are most sensitive to rays of light that strike orthogonal to the surface.

Question 21

Photoreceptors S M L rods

Answer 21

S-cyanolabe-440nm
M-chlorolabe-534nm
L-erythrolabe-564nm

Rods-rhodopsin -498nm

Question 22

Protanopes

Answer 22

Missing L cones
Confuse red, orange, yellow and green. They see red very dim.
Inherited

Question 23

Dueteranopes

Answer 23

Missing M cones.
Confuse red yellow orange and green
They do not have dim effect on red color
Inherited

Question 24

Tritanopes

Answer 24

Missing S cones.
Blue-yellow defect
Usually acquired

Question 25

Protanomalous trichromat

Answer 25

L con shifted toward short wavelength. Red orange green all appear Green. Red appear dimmer Red weak

Question 26

Deutranomalous trichromat

Answer 26

M cone shifted toward longer wavelength . Red orange green all appear more Red. Green weak

Question 27

Copunctal point

Answer 27

All color confusion lines originate from one point.

Question 28

Ishihara plates

Answer 28

Can only diagnose red-green defect.

Question 29

Farnsworth D-15 test

Answer 29

Diagnose red-green and blue- yellow defects. Doesn't distinguish between dichromats and anomalous trichromats.

Question 30

Nagel Anomaloscope

Answer 30

Can distinguish between dichromats and anomalous trichromats. Has test field (590nm, adjusted from 0-87) and mixture field (546nm and 670nm, adjusting from 0-73) Normal color vision = mixture scale to 45 and test scale to 17

Question 31

Protanopes result from Nagel test

Answer 31

Mixture of 73= will set the test field to very low settings. Mixture of 0 = will set the test field to very high settings Their mixture field fall on color confusion.

Question 32

Deuteranopes Nagel test

Answer 32

Mixture field anywhere from 0-73= test field will set to 73. | They don't have dimming of red.

Question 33

Protanomalous trichromat

Answer 33

Will have to set mixture field higher than normal settings which is 45. They will set the test to 10 Because they r red weak.

Question 34

Deuteranomalous trichromat

Answer 34

Will have to set mixture field lower than normal settings which is 45. They will set the test to 17 Because they r green weak.

Question 35

Blue-yellow defect

Answer 35

Outer retinal disease AMD Glaucoma

Question 36

Red-green defect

Answer 36

Inherited Inner retinal disease Optic neuritis, visual pathway disease.

Question 37

Chromatopsia

Answer 37

Characterized by distortion of colors but not a deficiency

Question 38

Visual pathway to detect motion

Answer 38

Primarily processed by the mangocellular pathway, V5 in middle temporal area.

Question 39

Motion after effect

Answer 39

Perception of motion after moving stimuli is removed, in most cases is in opposite direction of the original motion stimuli. Common example is WaterFall illusion.

Question 40

Example of low frequency cut off if temporal modulation transfer function

Answer 40

- purkinje tree - Toxler phenomenon Our visual system has poor sensitivity for very low frequency.

Question 41

Crowding phenomenon is the result of

Answer 41

Simultaneous masking effect

Question 42

Magnocellular pathway is responsible for

Answer 42

Saccadic suppression . | Damaged by glaucoma, which results patient with glaucoma may show decreased ability to process moving stimuli.