Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
71 Cards in this Set
- Front
- Back
what is vection
|
the illusion of motion of one's ENTIRE SELF as a result of motion in one's peripheral visual field
ex: sitting in a stationary car and cars around move foward. it seems like you are moving backwards |
|
what is the relationship between vection and illusory motion
|
although it can be caused by visual stimulation, vection is NOT considered to be a category of "illusory" (visual) motion
|
|
what are characteristics of eye/head motion perception
|
1. subject tracks stimulus with head/eye movement
2. retinal image of moving object remains stationary on fovea 3. info about obj motion involves muscular, EOM, and vestibular system. |
|
what are the characteristics of retinal motion perception
|
1. requires motion of the objects image across the retina
2. info about obj motion mainly within "visual" pathways |
|
what is the Troxler Effect
|
1. the perceptual disappearance of a STABILIZED RETINAL IMAGE
2. retinal image is stabilized when it moves exactly with the retina, REGARDLESS of any voluntary or involuntary movements of eye |
|
what is the relational between the human visual system and light stimulation
|
the human visual system is sensitive to CHANGES in light stimulation
|
|
under normal conditions...why can't we see retinal blood vessels
|
1. shadow of retinal blood vessels are stabilized retinal images.
2. they move WITH THE RETINA as the eye moves so their position on the retina DOES NOT change TROXLER EFFECT |
|
what is the Purkinje Tree?
|
PURKINJE TREE:
by causing a rapid oscillation of the shadows of the retinal blood vessel across the retinal, you can perceive the pattern of the retinal blood vessel. |
|
how is minimum amplitude of perceivable motion effected with retinal eccentricity?
|
INCREASES TOWARD PERIPHERY
foveal: ~20 arc sec or less 20 deg: ~3 arc min 40 deg: ~5 arc min *detect faster movements at the fovea |
|
how is the minimum VELOCITY of perceivable motion effect with a nearby stationary reference stimulus?
|
1. ~10X better in the presence of a nearby stationary reference stimulus
2. ~1-2 arc min/sec WITH reference 3. ~10-20 arc min/sec WITHOUT reference *decreases with increasing luminance |
|
what are the FIVE ways by which an object might appear to move
|
1. real motion
2. autokinetic effect 3. induced motion (motion contrast) 4. aftereffects 5. stroboscopic motion |
|
what is the autokinetic effect
|
illusory motion in which a small, stationary object viewed against an otherwise COMPLETELY featureless visual field, will appear to move about randomly within a small area
ex. small, station point of light viewed in the dark will seem to move |
|
what is induced motion
|
1. illusory motion in which a stationary object appears to move due to the motion of surrounding obj or contours
2. always perceived to be in the direction opposite to that of the inducing objects example: moon appears to be moving in the opposite direction of cloud movment |
|
what is motion contrast
|
1. a special case of induced motion
2. only operates across very short distances |
|
why do we see motion with repeating asymmetric patterns
|
NEURAL IMAGE CONTRAST
1. high contrast points in the optical image are registered BEFORE low contrast point 2. ration of neural responses in the high and low contrast areas of the neural image change over time 3. apparent shift in phase is what activates the local velocity detectors |
|
what is the difference between motion ADAPTATION vs. motion AFTER EFFECT
|
1. adaptation: illusory changes in the perception of motion that occur DURING prolonged viewing of moving objects
2. after-effect: illusory perception of motion of stationary objects OR changes in the perception of motion of moving objects AFTER prolonged viewing of moving objects |
|
waterfall illusion is an example of...
|
MOTION AFTEREFFECT
|
|
what is velocity adaptation
|
prolonged viewing of an object moving at a constant velocity may cause a DECREASE in the PERCEIVED speed of motion
|
|
what is direction specific adaptation
|
motion detection and contrast detection threshold INCREASE during prolonged viewing of moving objects but only for objects moving in the SAME/SIMILAR direction
|
|
what is stroboscopic motion
|
apparent motion:
1. resulting from the successive presentation of a stimulus at different locations along a continuous path 2. example lights going around a marquee |
|
what is KORTE'S LAW
|
1. describes the relationship among various stimulus parameters necessary to maintain optimum PHI motion when any one parameter is changed
|
|
what is first order motion
|
movement of areas that are defined by their LUMINANCE
|
|
what is second order motion
|
movement of areas whose contours are defined by TEXTURE
NOT LUMINANCE |
|
what is third order motion
|
1. motion defined ONLY by difference in COLOR!!
2. motion defined as figures with NEITHER LUMINANCE NOR TEXTURE boundaries 3. PARVOCELLULAR PROCESSING |
|
what are the SEVEN characteristics of NORMAL neonate vision
|
1. small eye (~16.5mm)
2. clear ocular media 3. reasonably good image quality 4. hyperopia and astigmatism common 5. small pupils (miosis) 6. poor control of accomodation 7. foveal photoreceptors are wider, shorter, and more widely spaced than in adults |
|
what is coherent motion
|
1. motion of elements that all share the same velocity of motion
2. form from motion 3. Gestalt organizing principal (common fate) 4. evaluates mainly MAGNOCELLULAR processing 5. elevated thresholds in glaucoma and ONH disease |
|
what is the braddick limit
|
1. maximum displacement threshold
2. typically ~15 arc minutes |
|
what is short range motion
|
1. SECOND order stroboscopic motion
2. within Dmin and Dmax range 3. SOA<100 msec 4. NOT perceived with DICHOPTIC STIMULATION or bright ISI |
|
what is long range motion
|
1. FIRST order motion
2. operates with displacement larger than Dmax 3. SOA 100-500 msec 4. works WITH DICHOPTIC stimuli and with bright ISI |
|
what does short range and long range motion rely on?
|
both are believed to rely heavily on MAGNOCELLULAR PATHWAYS
|
|
what is aperture problem?
example? |
1. receptive fields of neurons signaling visual motion function as viewing apertures
2. the aperture itself can influence perception of the direction of motion within example: Barber Pole Illusion |
|
visual illusions
|
erroneous perception due to incomplete, ambiguous, or contradictory visual information
|
|
what are some theories that support object recognition
|
1. feature analysis (bottom up)
2. global processing (top down) 3. computational models (newer bottom up) 4. feature integration theory (BOTH) |
|
what is analytical introspection
|
STRUCTURALISM:
identify the smallest set of PRIMARY SENSATIONS necessary to uniquely identify any object ex: a bunch of dots making up a picture |
|
what are Pandemonium Models?
this is an example of... |
FEATURE ANALYSIS:
1. feature demons find vertical lines, acute angles, etc. 2. cognitive demons have ideas about the features of their letters 3. decision demon identifies the letter based on which cognitive demon "yells the loudest" |
|
what are GEONS
|
GEOMETRIC ICONS
1. non accidental features, equally recognizable regardless of orientation 2. structures composed of geons should be "viewpoint invariant" 3. we recognize objects by recognizing the spatial combo of the various geons |
|
most eyes growth happens within...
|
the first 6 years
|
|
what ethinicity tends to be more myopic
|
ASIANS
|
|
what is the most important factor that leads to emmetropization
|
time spent outdoors is most important for proper emmetropization
|
|
how does form effects myopia
|
1. depriving the eye of form vision promotes axial elongation and myopia (chronic image degradation can cause myopia)
2. the ocular changes in FDM are similar to those associated with childhood myopia 3. the potential for a clear retinal image is essential for normal refractive development |
|
what is the role of optical defocus in treatment of refractive error
|
1. optically imposed myopia:
to compensate, the eye must become more hyperopic 2. optically imposed hyperopia: to compensate, the eye must become more myopic |
|
what happens with under corrected patients
|
1. under correction DOES NOT prevent myopic progression in children
2. they actually will become more myopic |
|
what is the consequence of traditional correcting lenses
|
as a consequence of eye shape and/or aspheric optical surfaces, "corrected" myopic eyes often experience significant HYPEROPIC DEFOCUS across the visual field
|
|
AN INTACT FOVEA IS NOT ESSENTIAL FOR NORMAL EMMETROPIZATION
|
AN INTACT FOVEA IS NOT ESSENTIAL FOR NORMAL EMMETROPIZATION
|
|
what are the implications of human studies of emmetropization
|
1. contribution to myopia, concentrate on factors that are very CONSTANT over time
2. peripheral vision should be considered when assessing the effects of visual experience on refractive development 3. peripheral vision should be taken into account in order to optimize optical treatment strategies for myopia 4. inaccurate accommodation is significant risk factor in myopia 5. spending time outdoors is good for emmetropization |
|
what is a better why to correct myopia
|
by increasing the effective curvature of field it would be possible to correct central errors and either correct peripheral errors or induce peripheral myopic defocus
|
|
photoablation of the fovea does not...
|
photoablation of the fovea does not...
1. interfere with normal emmetropization 2. prevent recovery from induced refractive errors 3. prevent form deprivation myopia 4. prevent compensation for optical defocus |
|
what are some normal changes of the pupils and lens with increasing age
|
senile miosis:
1. decreased in retinal illumination 2. increased depth of field Lens Change: 1. Presbyopia: decrease in AA 2. yellowing of crystalline lens 3. increased light scatter |
|
what are some normal changes in refractive error with increasing age
|
1. "with" to "against" the rule shift in astigmatism
2. increase in myopia 3. NO significant change in macular pigment density |
|
what happens to luminance to the retina as we age
|
1. reduced light transmittance through smaller pupils
2. less light due to lens change 3. perceptually not tramatic because of light adaptation |
|
what happens to spectral sensitivity as we age
|
1. decreased sensitivity for all wavelengths
2. greater decrease for short wavelength sensitivity |
|
why does the short wavelength sensitivity decrease more with age
|
1. yellowing of the lens
2. greater sensitivity of SWS cones for metabolic damage (diabetes) |
|
how is color vision affected with age
|
1. increase in tritan abnormailities
2. evident in DESATURATED D-15 testing 3. secondary to yellowing of lens, increased macular pigment density and metabolic disease |
|
how is contrast sensitivity affect with increasing age
|
1. decrease beginning ~65 yrs.
2. mainly for midrange and high spatial freq 3. due to miosis, lens and vitreous change, as well as increase in density of macular pigment and neural factors |
|
how is visual (recognition) acuity impact with age (IMPORTANT)
|
1. mild decrease in high-contrast recognition acuity beginning around 60-65
2. significantly greater decrease found in LOW CONTRAST recognition acuity *snellen chart DO NOT adequately reflect an older patients loss of visual function in the real world |
|
what are two clinical test for disability glare
|
1. brightness acuity tester (BAT)
-high contrast acuity with glare 2. Berkeley Glare Test -low contrast acuity with glare |
|
what happens to disability glare with increasing age
|
1. decreased spatial resolution in presence of bright, surrounding light
2. largely due to LIGHT SCATTER |
|
glare recovery with increasing age
|
1. time to read two lines larger than before on the low contrast SKILL card after exposure to bright light
2. ~8x increase from ages 60-80+ |
|
what happens to flicker perception as we age
|
1. gradual decrease at ~20 years
2. larger decrease at ~70 years 3. both CFF and sensitivity decreases are due to neural factors |
|
at birth what does the normal eye look like
|
1. small eye (16.5mm)
2. clear media 3. reasonably good image quality 4. HYPEROPIA and ASTIGMATISM 5. small pupils 6. poor accommdative control 7. photoreceptors are wider and shorter |
|
the first eye movements are...
|
1. reflexive
2. saccadic *existence of these early eye movements is that the neural pathways serving them must exist at birth |
|
newborns and tracking
|
infants show little smooth pursuit tracking and mostly SACCADIC TRACKING
|
|
what pathway is utilized in OKN and smooth pursuit
|
1. different NEURAL PATHWAYS (subcortical) than those involved with conscious perception
2. OKN can exist in people who are perceptually blind |
|
what eye movement bias does newborns exhibit
|
1. NASAL BIAS
2. better OKN and smoother pursuit for T-N motion than N-T 3. normally disappears within first 3-5 months 4. persist in infantile onset strabismic amblyopia |
|
spectral sensitivity and color vision in new borns
|
1. scotopic/photopic spectral sensitivity (adult shape by 1 month and adult sensitivity by 6 months)
2. R/G discrimination present at 2months (adult level by first year) 3. B/Y develop more slowly |
|
what is the contrast sensitivity timeline for newborns
|
1. 0-10wks: improvement at all spatial freq
2. by 2 months: lateral inhibition 3. by 6 months: peak of CSF at adult position 4. ~5 years: increase sensitivity in high spatial freq and cutoff spatial freq |
|
when does stereopsis mainly develop in newborns
|
1. little to no stereopsis before 3 months
2. EXTREMELY rapid development between 3-6 months |
|
what happens in the first six months of development
|
1. CFF
2. scotopic/photopic luminosity 3. absolute light sensitivity 4. spatial freq of max contrast sensitivity 5. stereopsis (threshold ~1arc min) |
|
what happens within the first year of development
|
red/green color vision development
|
|
what happens between 3-12 years of development
|
1. fine spatial resolution
2. fine relative spatial localization |
|
in art what gives rise to depth
|
THREE DISTINCT CHANNELS:
1. form 2. color 3. movement |