Binocular Vision Flashcards

Terms Definitions
egocentric
binocular directionality
Binocular Visual Phenomena
Pulfrich Phenomenon
Fechner's Paradox
Binocular Rivalry
Binocular Color Fixture
stereopsis
small differences in perceived horizontal direction btw the 2 eyes give rise t a 3d percept
Horizontal disparity
horizontal differences in retinal image position * more impt*- allows the perception of stereoscopic depth - can be crossed or uncrossed depending of fixation pt
Oculocentric
"eye centered" visual direction so that as the eye shifts position so does the oculocentric direction - is determined by the line of sight of an object thru the nodal pt. of the eye to the retina
Binocular Rivalry
large differences between the images on the rwo retinas cause a fight for dominance thereby resulting in alternation suppressions of parts of the eye.
Past Pointing
visual direction is dependant on feedback from other sensory organs and may be altered under certain cirumstances
Diplopia and Confusion
images on widely separated noncorresponding pts or pt beyond Panum's area will not be seen as fused or single
Binocular confusion
two different objects seen in one direction or location
UNCROSSED DISPARITY
-points further away than the fixation pt. have lines of sight that meet behind the fixation pt. - angle n is negative - AR is larger than AL - nasalward shift
Binocular Summation
VA and contrast threshold is better with 2 eyes
sensory fusion
integrate the images of objects viewed by the 2 eyes as a single image
Corresponding Points
places in the two retinas giving rise during binocular vision to the localization of sensations in the same visual direction.
Pulfrich Phenomenon
1 eye covered by darkened lens and watches a pendulum swing from side to side but instead perceives an elliptical path rather than the linear one. Neurons in brain integrate the info from monocular targets that are on non-corresponding points and so the patient sees the target displaced in depth.
VISUAL AXIS
visual line that passes from the fovea to object of regard
CROSSED DISPARITY
pt. seen as nearer than the fixation pt, fall w/in Vieth-Muller circle, and have a line of sight that cross in front of the fixation pt.positive AL is larger than ARtemporalward shift of images in one or both eyes
interocular distanceseptum
60-65 mm; why we see 2 different scenes mono,the image on the retina's of both eyes are NOT indentical nose divides and cuts the extreme nasal part of each eye's VF
common subjective principal visual direction
zero reference for bino directionoriginates from a pt. midway b/w the two eyes
Eccentric fixation
point other than the fovea is used for fixation- common consequence of strab's and contributes to vision loss of amyblopia- a pt. who fixates at an extrafoveal retinal locus does not necessarily have eccentric fixation - neurological remapping of monocular principal visual direction to a new locus
Binocular VFTemporal cresents
overlapping part of the VF is seen by both eyes at the same timelies b/w the temporal cresentsVF seen by one eye alone
Corresponding retinal points
pairs of points, one in each eye that when stimulated simultaneouly or in rapid succession are perceived to lie in a single common visual direction
Binocular Color Mixture
 
Red on Right eye, Green on left eye = observe perceives Yellow.
Improper conditions to see singly:1. diplopia2. binocular rivalry3. Binocular suppression
each eye's image does not combine fully but instead fights to win out over the other eyes image- one eye shuts off
LOCAL SIGN made possible by :
capacity of visual neurons to process direction Retinotopic mapping of neurons in the visual system and labeled lines- an image formed on a specific retinal location will stimulate a retianl location, LGD, or striate cortex
Law of headcentric localization
for a given postion of the eye in the head, objects lying on the same line of sight are seen in the same headcentric visual direction
diplopia
misalignment of the eyes
Horopter
experimental determination of the projectin of corresponding points in space
Visual Direction
is a relative judgement
Stereoscopes
(presents independent info to the two eyes)
Wheatstone Mirror Stereoscope
Prism Stereoscope
Anaglyphoschope
Polaroids
Pseudoscope
Telestereoscope
Autostereograms
EGOCENTER
under bino conditions we see directions not relative to each eye alone but relative to this single reference point w/in our head
Depth Constancy
Observer perceives a constant amount of depth from a 3-D stimulus that is coming closer to the observer and presenting increasing amount of disparity as it approaches.
eye dominance
reflects the relative weighting of each eyes input into the bino precept
Depth perception
arises from the stimulation of noncorresponding retinal pts.
Crossed diplopia
distant object is fixed bifoveallya nearer object in front of it will be imaged on the temporalward retina of each eye on noncoressponding pt. -- if these pt are far enough we see double
Human have VF that overlaps :
120 degrees
uncrossed diplopia
near object is fixated, a distant object is seen as double each image is formed on the nasal retina
Secondary Visual Direction
area's around the fixation ptsignaled by retinal pts eccentric to foveart, lt. above below fixation pts
Eccentric viewing
requires conscious effort on the part of the ptit occurs after loss of vision from injury or DZ it is a normal adaptation to the visual loss rather than an abnormality
Directionality
what direction the light of an image is coming from used to build an interpretation of the 3D world ( visual space)
Fechner's Paradox
 
1 eye is covered with darkened lens and when removed actually views the environment as less bright  instead of more bright since uncovering the eye, its visual system is being stimulated w/ increased total retinal illuminance.
Stereopic Depth Perception
The greater the disparity, the greater the perceived depth.
related: stereopsis, disparity, crossed disparity and uncrossed disparity
EGOCENTRIC LOCALIZATION
we see objects whose images are formed on both fovea's as if their images instead fell on a single pt. midway btw the 2 eyes;
Vieth-Muller Circle
plot of points in visual space and their corresponding retinal pts,
Headcentric directionality
knowledge of the position of the eyes in the head
Principle visual direction
- reference in which we compare all direction zero direction direction signaled by the fovea/where the eye is fixating
Aiming of the 2 eyes can produce:Use of two eyes gives -->
amblyopiasuppresion diplopiaLarger field of view
diplopia and confusion may be eliminated in a strab visual system by :
1. suppressing2. shifting the zero reference pt. for directionalty in the strab. eye
panoramin vision
no overlap b/w the 2 eyes and can see almost 360 around them
Law of identical visual direction
objects with same visual direction in each eye will be seen as lying in a single visual direction under bino viewing conditions-fovea 's of the 2 eyes signal the same primary visual direction
Real advantage of bino vision :STEREOPSIS
bino form of depth perceptionallows more precise hand-eye coordinationgrasping near objects is more accurate under binolower detection thresholds increased VA
Limits of depth perception :1. steroacuity 2. panum 's ranges
small depth without loss of fusion largest depth without loss of fusion
Binocular disparitytoo large of a bino. disparity
difference in position in relation to corresponding pt. bw images in the 2 eyeDIPLOPIA
What does visual brain do when images on the 2 retinas are different?
1) stereopsis
2) integrate the two images so both are simultaneously used for single vision
3) avg. the luminances of the 2 images
4) use info to create new perceptions
5) suppress one of the images (binocular rivalry)
Can judge some things with mono cues to get depth perception ( depth is still better bino)
- perspective- occlusion - elevation - texture gradient- motion parallax
Surgery
N
Occlusion
N
Added lenses
N, crutch
Accommodative Excess
accommodation exceeds demend
UNCORRECTED HYPEROPIA
spasm
PSUEDOMYOPE
accom hysteresis
CI - using accom to dec exo
idiopathic
Towards end of day near complaints, difficulty focus at distance (esp after near work)
NORMAL AA
poor + MAF
LOW lag
low NRA w/ norm BO
Maybe ESO w/ low BI to blur
VT (not organic causes)
Y
Sprectrum of BV
Clear/single/comfortable/efficient/BV
Decreased Quality of Fusion (get last)
Decreased stability of Fusion
Abnormal AC/A relationship
Loss of Fusion with good monocular skills
loss of unilateral monocular skills (get first)
CycloVertical Symptoms
Ocular - Pulling, itching, asthenopia
Blur, Diplopia, Reading difficulty
Fatigue, Nausea, vertigo (esp car sickness)
Perception
Appreciation of a physical situation through one or more of the senses.
What does increased temporal frequency do to the fusion limits of a low spatial frequency object?
decreases them
Duanes Syndrome
non-commitant horizontal: type 1: more innerv to med rectus; type 2: retraction on adduction, more innerv to lateral rectus; type 3: retraction on adduction but more innerv to lateral rectus
paresis of abduct, adduct or both
congenital
assoc w/: torticollis/ hearing and facial-vertibral anomolies
Drugs that cause accomodative dysfunctions
Insuff/infacilty:
ANS (parasympatholytic/sympathomimetic)
Alcohol/weed
Phenothiazides
antihistmaines
CNS stimulants (ADD meds)
Artane (parkinsons)
Excess:
ANS (parasympathomimetic/sympatholytic)
Morphine
Digitalis (HR)
Sulfonamides/Carbonic ANhydrase inhib
Induced effect
The spatial distortion created when using axis 180 magnifier. In general, the induced effect is 2/3 of the geometric effect for the same lens.
Which degree of fusion includes deriving a three dimensional depth perception, or steropsis?
Third Degree fusion
classifications of Accomodative Dysfunction
1. Accom Insufficiency - ill-sustained, paralysis, unequal
2. accom excess
3. accom infacility
classification schemes
Time of onset: early aquired(4-6 mn) late acquired(2yrs)
Mode onset: acute/ progressive/ constant/ intermittent
Size: Microtrope(<10-15), mod (10-30), Large (>30)
AOA - has gaps: infantile, acquired, secondary, adn micro eso and exo trope (8 classes) 
ICD-9: follows money, doesnt have all trope options
CEMAS-8: Ocular motor dysfunction, sensory, horizontal trope, horiz phorias, cyclovert trope, cyclovert phoria, accom dysfunct, nystagmus
Other: direction, accom/refract, duane-white, Disease, pseudostrab (lid, inner canthus)  
Amblyoscope test for strabismus
Measures at optical infinity
Alternate Exclusion (ACT) - 2 images, one OD and one OS, alternatly occlude and move until no eye movements
Corneal light reflex (krimsky) - fixate OD adn move light on OS til reflection is 0.5mm nasal
defn of cured
bifoveal fixation in 99% ADL
clear vision, gen comfortable
bifixation in all gazes and a few cm NPC
reasonable corrective lenses and prism
stereopsis
Horopter point
A point in objective space whose images fall on corresponding retinal points
What is the process by which two images, one from each eye, give rise to a unified percept of one single object?
Binocular fusion
Which type of disparity is difficult for someone with an esofixation disparity to handle?
Uncrossed fixation disparity
What is it called when a patient is presented with images on corresponding retinal points, but makes eye movements so that the images are no longer on retinal points and thus discourages sensory fusion?
horror-fusionalis
risk factors or strabismus
>30%+4D uncorrected hyperopes by 3yo become ET
50% down syndrom
44% cerebral palsy
90% craniofacial dysostosis
genetics, 10x more likely, 23-70%
Purpose of description of strabismus
to classify
accurate documentation - audits and baseline
to plan management
Normal AC/A - Basic ESO
POOR direct/indirect NFV
diplopia not blur
Inc MEM
USU. HYPEROPES, maximize +
vert prism
add lenses moderately affective
**HORIZONTAL prism - better than for exos
occlude for amblyopia
VT
surgery
Image space of eye
Space in eye which received electromagnetic vibrations in a specific range of frequencies. Light transmission in the eye. Space that gathers information.
how Testing no commitant
occlude suspect eye and only measure that eye NOT both
subtypes of Accommodative Insufficiency
1. Ill-Sustained - NORMAL amps!, low PRA, fails - MAF on repeatitions, Large lag, ESO @near
2. Paralysis - pre-presbyopes, FRANK dec mono/binoc amps, Fails NRA/PRA bc starts with blur!, Large lag, Fails + and - facility
3. Unequal - Poor balance/adies/neurological, reduces ASYMETRIC amps, May PASS nra/pra, large ASYMETRIC lag, Fails MAF (+ and/or -)
Defn of Strabismus
Loss of FUSION, w/ or w/o muscle alignment
Suppresion/diplopia can be 1st, 2nd, 3rd degree
What do you call a precise shifting in corresponding points that matches the angle of strabismus?
Harmonious anomalous correspondence
Accomodative Dysfunction - Physiology/phrmacology
increase in power of lens to see objects @ near
Accom controlled by ANS - primarily the parasympathetic (fast-Ach), causes miosis, convergence via CNIII,
Sympathetic system inhibits accom (SLOW), dilates, use parasympatholytic and sympathomimetic (PE)
Bruckner test for strabismus
using oscope dial in to make face clear and look at both reflexes, supposed to be equal
if unequal, brighter reflex is strabismic eye
Object space of eye
Receptive field of the eye, the space containing objects which may be imaged in the eye. Light transmission outside eye. Space that contains information.
If a strabismic patient suppresses what type of fusion is inadequate?
Both motor fusion and sensory fusion are inadequate
What are the twelve factors that influence Panum's fusional area?
CLIT SAT (EST)21. contrast-no effect2. luminance-change in luminance 3 log units above threshold has little effect3. interocular inequality-Panum's fusional area decreases with increasing interocular inequality4. target orientation-hard to quantify5. eccentricty6. spatial frequency7. the influence of other objects in close proximity-like the crowding effect, closer objects reduce Panum's fusion area size8. Exposure duration-Panum's fusional area increases with exposure time9. Spatiotemporal frequency-larger Panum's fusional area with low spatiotemporal frequency10. Temporal frequency11. Small angle strabismus12. Anomalous retinal correspondence
What is the neurophysiological and psychological process by which the visual cortex combines thesuperimposed views obtained independently by the two eyes into one unified percept of visual space?
Sensory fusion. It is a perceptual phenomena. see p. 46 text
How big is Panum's fusional area at the fovea?
5 to 20 minutes of arc
What type of strabismus is usally present in children?
Esophoria, while adult onset is more often exophoria
Based on the nonius lines, how do we know that Panum's fusional area exists?
The nonius lines (presented monocularly) can be seen nonaligned one on top the other, while the binocularly presented target that encompasses the nonius lines is still seen as single.
What are three reasons the alternate or suppression theory does not hold true?
1. Insufficient time to switch between eyes and maintain stereopsis2. We can experience steropsis in less time than it takes to switch attention. 3. Regardless of which eye is stimulated reaction time is the same.4. No apparent motion
Accom XS and Conv XS
If ahve accom XS maybe eso bc over accomodation could drive the convergence system into overdrive
What are two potential results of the visual system being unable to fuse images?
1. Anomalous correspondence 2. Suppression
What are the six tests to measure fixation disparity?
BAM BWD1. Mallet box-oldest2. Bernell Test Lantern-Distance and Near3. AO Vectographic Slide-distance only4. Borish Card-Near only5. Wesson Card-Near only6. Disparometer-Near only
Why do you start using a target that stimulates the peripheral retina when you are training a patient to fixate?
Panum's fusional area is bigger in the periphery and peripherally viewed objects are easier to fuse.
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