lecture 1- intro to bv Flashcards
what is binocular single vision? (BSV)
fusion of 2 images from each eye to form one single image
What you need to achieve normal BSV?
normal retinal correspondence (NRC)
advantages of BSV
- binocular summation
- depth perception/stereopsis
what is normal retinal correspondence ?
every point in the retina corresponds to a certain point in space
nasal retina corresponds to …
temporal VF
temporal ret corresponds to ..
nasal VF
superior ret corresponds to …
inferior VF
inferior ret corresponds to ..
superior VF
BSV grading (Worths grades)
- simultaneous perception
- sensory fusion
- motor fusion
- stereopsis
what is the horopter?
objects that stimulate corresponding retinal points lie on the horopter (imaginary line) and are seen as single
what is the Vieth-Müller circle?
the theoretical horopter in the horizontal plane
what is panums fusional space?
small area around the horopter where almost corresponding objects are still seen as single
why are objects seen stereoscopically in panums fusional space?
due to slight retinal disparities
is diplopia normal ?
when objects fall outside of panums fusional space
what is simultaneous perception
ability to perceive 2 images simultaneously, one from each retina
what is sensory fusion
Integration of two similar images, one formed on each retina into one image within the brain
for sensory fusion to occur the images have to be similar in..
brightness
size
form
what is motor fusion
Maintenance of sensory fusion through a range of vergence movements
what is stereopsis
The perception of relative depth of
objects by the fusion of relative
disparity of images from the two
eyes
confusion (NRC)
fovea of fixating eye and fovea of strabismic eye receive 2 diff images and they are superimposed
pathological diplopia
fixating object stimulates fovea in one eye and peripheral retina in the strabismic eye
pathological diplopia occurs in which type of strabismus
manifest
is confusion or pathological diplopia more common in adults to develop strabismus
pathological diplopia
when do you get suppression
under 8 years old
what is suppression
mental inhibition of the image in front of the eye which is deviated off
visual cortex ignores the extra image
if you have suppression, do you have stereopsis?
no
what is abnormal retinal correspondence
Sensory adaptation in which the fovea and areas on nasal and temporal retina correspond and have a common visual direction with an area other than the fovea with the deviating eye
basically you have a pseudo fovea
do you have BSV with ARC
no, you have abnormal binocular single vision
do you have stereopsis with ARC
yes
do you have binocular summation with ARC
yes
when you cover one eye with Px with ARc
they use their normal fovea not Pseudo therefore they move their eye (out for eso, in for eco)
do you treat children with constant strabismus
if they have suppression- you may want cosmesis surgery
if they have ARC - monitor
do you treat adults with strabismus?
prisms, lenses or surgery
what will a 50 year old px with recent onset constant right esotropia normally experience?
uncrossed diplopia
if you have a 6 year old with moderate right esotropia (ARC) can you use prisms or surgery?
no, they will get diplopia as they want to use their pseudofovea
if you have a 6 year old with moderate right esotropia (suppression) can you use prisms or surgery?
no, they will get diplopia as they want to use their pseudofovea
but
if you have large angle strabismus consider surgery for cosmesis
how to explain suppression to a parent and child
both your child’s eyes are working, however they do not work together
when both eyes are open they either use their left eye or right eye (not both)
she does not use both at the same time
this means she prob finds activities where she is required to judge distances of objects harder than other children eg. ball sports like netball, basketball etc
