Exam 3 - Week 7 to 9 Flashcards
What retinal cones are functional for a Protanopic individual?
No Red (L cone) and cannot detect dark red preception, thus it is considered as nothing
Blue and Green
What retinal cones are functional for a protanomalous?
Blue, Green and Green shifted
What retinal cones are functional for a Deuteranopic?
Blue, Red and shifted to red (Missing Green cones)
Note: Has the highest frequency at 5%
What retinal cones are functional for a Tritanopic?
Green and Red
Note: All blue is missing and is extremely rare.
What retinal cones are functional for a Blue cone monochromcy?
Blue
Note: Cannot see color
What retinal cones are functional for a Achromatopsia?
None
Note: Very rare. Usually congenital, photophobic, nystagmus, VA is 20/200 or worse (best corrected), usually found in family members
What are the 3 inherited color blindness?
Monochromacy - Either Rod monochromat or Blue monochromat
Dichromacy - Protanopic, Dueteranopic and Tritanopic (two functional cones - which have color perception)
Anamolous trichromacy - Protanomolous and Dueteranomolous
What island is known as the color blind?
Pengelapese, the ratio is 5% of the population is color blind
Note: An irish gave off the gene. Dogs have a similar form of color blindness
Can an individual have a monochromacy but with issues to their cones?
Yes, the short wavelength is the only one function. They will pass ERG, Visual Field and EOG will be passed. GREEN AND RED ARE ABSENT
Note: Cannot distinguish hues and is an X linked recessive gene (1 out 1000 individual will have this)
What is the percentage of blue cones in the retina?
2%, this is remarkable for monochromats.
How many hues can a monochromat see?
100
Which two dichromacy are sex linked?
Protanaopia and Deuteranopia (Usually in males)
When we test for color blindness, which test is common practice?
Ishihara test
What are the lines that go right through the CIE diagram for color?
Confusion line - shows where color confusion occur for Dichromats
What are the 3 anomalous trichromacy?
Protanomoly
Duetranomoly - most common type (on test) (green shifted towards red)
Tritanomoly
Note: Most common. Will depend on shift of damage, they are inherited
How do we test for most of color deficiencies in clinic?
Farnsworth test
What is the function an Anomaloscope?
Finds the color deficiency and even further find out what subtype is actually missing.
What is the difference between visual acuity and spatial acuity?
There is no difference. VA is the spatial resolving capacity of the visual system.
Note: It can also be the smallest spatial detail that can be resolved
What part of the snellen “E” forms a small grating pattern?
Stroke
Note: There are 2.5 cycles of black and white (30 cycles for 20/20 vision)
Whats the equivalent of 1 minute of arc?
6meters
Note: 6/6 = 20/20
When measuring acuity, OD’s characterize VA as in “20/20” vision, but how do scientists measure VA?
Smallest Visual Angle of a cycle of grating
“The smaller the Visual Angle at which you can identify a cycle of a grating, the better your vision
What formula do you use when you want to detect the smallest angle possible?
cpd = 1/2(arctan(s/2f))
How many cones are needed when distinguishing Acuity?
2 is the minimum
What is the typical VA in cycle degree?
30 cycles per degree
True or False. If you have 3 or more cones, you will be able to distinguish the difference between spatial resolution?
True
True or False, the higher the degree, the better the VA will become?
True
What are 3 issues that affect VA?
Myopia, Hyperopia and Accommodated hyperopic eye
True or False. Visual acuity is greater than Spatial acuity?
True
When Dr. Cameron was showing the “Hyper Acuity”, what is the difference vs. spatial acuity?
Hyper acuity is 5 to 10 times better
What is size constancy?
Objects of known size tend to appear constant in size despite distance changes
What is the maximum our vision can interrupt, in regards to degrees?
150/60 degrees
What is the spatial frequency for 20/20 vision equivalent to?
30 degrees
Can OKN be a good subjective measure for vision?
According to the VA suppression method
What is the measurement for temporal frequency?
Hz
Note: Measured as cycles/second
What s the basic stimulus used to study temporal vision?
Flickering light
What is the Ferry Porter law?
CFF increases lineraly with log BACKGROUND
What is the Granit Harper law?
CFF increases lineraly with log STIMULUS area
What is the scientific name for the “light house effect”?
Broca-Sulzer
Note: Measure in lux and you notice information around 100 milliseconds @ 44.5 lux
In regards to the critical flicker test: wagon wheel, what is the fusion flicker response at a stand still?
120 rpm
True or False. You can increase your CFF rate by increasing their metabolic rate?
True
True or False. There is an increase in CFF with animal size?
False. It will decrease.
Of the 40 M diseases in the US, what are these disease that are clinically relevant in regards to CFFF?
Optic Neuritis
MS
Diabetic Retinopathy
Sleep Apnea
What is the Ferry Porter Law?
Noting that CFF is proportional to the logarithm of the luminance of flickering stimulus (L)
INCREASES LINEARLY WITH LOG BACKGROUND
What does the Granit-Harper law theory explain?
CFF increases linearly with log stimulus size or diameter
True or False, CFFF increases with illumination?
False.
Note: Plateau is around 40Hz, which is what the human eye can detect for flicker
True or False. Only rods are distinguished at a larger test field?
False. Cone and Rods both require this.
Note: As the TV screens get larger, the Hz needs to increase as well
During color and orientation processing, what occurs to the temporal resolution and integration interval?
High Temp. res.
Short Integration interval
During the binding process, what happens to the temporal resolution and integration interval?
Low temporal resolution
Long integration interval
Note: Pairing is used
What is motion?
Movement or change in position or place
d = vt
What does Beta motion do?
switching motion from on and off (slower motion)
What does Phi motion ?
A flicker occurs, goes on and then off(Rapid)
If there is an after image and rotates in circle. You see the color, what kind of process is it?
Magno (creates an after image)
What is Sigma Motion?
Flickering of a stripes, which look as though they are moving
Where does motion perception occur the most in primates?
Cortex
What is the visual pathway for Motion perception?
Parasol cells –> Magno cells –> v1 (mostly complex) –> MT –> MST
What is the percentage of cells that are direction selective (complex)
25%
True or False. All cells in the MT are direction selective?
False. Majority are direction selection but not all
What is Akinetopsia?
Motion blindness
What is relative size?
Judging due to past experiences but we try to use size constancy on our retina.
Ie. Cars in the street
What is size constancy?
Where an image be look the same size but in reality it is smaller than the object
What is Familiar size?
From your past familiar images tell you to perceive an image but you cannot always trust it
IE. Stealth bomber
What is Linear perspective?
An angle that is smaller will be perceived smaller on the retina
What is texture?
Relative size is the same but the perception is further and looks larger
Ie. Checkered balls
What is interposition?
Process of occulusion which blocks one item over another, therefore depth is created due to position
Ie. King of spades behind King of clubs
What is Clarity?
Form of interposition, acts as a depth cue.
Ie. Fogging of light house
What is lighting and shadow?
Illumination and shadow cause an illusion of depth. Light and shadow are always opposite of one another, therefore an optic shadow is created which makes an image to perceive its either behind or in front.
Ie. Mountain range with shadow
What is the angle of declination below the horizon?
How big the angle relative to the horizon
d= h/tan(a)
Angular declination is _______ in the prism condition
Increased
True or False, Angular declination is decreased in the after effect condition?
True
What type of function confirms that angular declination is a depth cue for distance judgement?
Monotonic
What is motion parallax?
Both Monocular and Binocular vision, Objects that are further away tend to move slower, compared to the closer object.
Note: You can fixate on object and it can be slower than without focusing on the object
When you track something while driving
What is Kinetic Depth Effect (KDE)
Illusion of depth is enhanced due to motion
What is the definition of a psychophysical test?
Perception arise from a physical stimulus
What are three psychophysical methodologies?
Threshold - VA, Contrast sensitivity
Signal Detection - Visual Field,
Weber’s Law - the 2nd part of the line graph
What is the smallest light intensity a pt. can detect test be considered?
Threshold
What is Accuracy of the Threshold?
Correctly measuring the value
Ex. IOP closer to one is more precise
Note: MORE IMPORTANT THAN PRECISION
What is Precision of the Threshold?
Repeatablility of measurement
Ex. IOP 15, 14, 16 is more accurate than 9, 12, 17
Do ganglion cells have a constant steady state?
Yes. to depict homeostasis
What are the variables for threshold variable?
Neural Noise, Patient (different approaches for all pts of their attention), Motivation and Fatigue
What is the staircase approach?
Graded steps (usually equal) and ask the “do you see the spot on the background”
What is Signal detection theory?
Model and data method for decision problems with uncertainty (noise)
Note: Finds point of interest
What type of eyecare is considered psychophysics?
Optometry
If you the rows are equal in the Signal Detection, what does that mean?
No detection
