alignment:
Infants appear to be ___tropic before 2 months of age
- due to large angle ___
- most infants are ortho around __ weeks
- ALL infants are less than ___ diopters exotropic; and their tropias are ALWAYS ____ (if existent)
EXOtropic
- KAPPA
- equal exo in each eye allows nml development
- 6 weeks (or ABOUT 1 month)
-20 diopters; always INTERMITTENT
Which comes first: convergence/binocularity or ortho alignment?
unknown.
At what age is convergence to an approaching object both accurate and consistent? What type of convergence was occurring BEFORE the approaching object?
-proposed that convergence occurs d/t the development of what?
3-4 months
-accommodative convergence - present
-ocular DOMINANCE columns
intermittent convergence occurs before 12 weeks (4 months) d/t what type of functional convergence?
accommodative
-convergence is absent @ 6 wks; suddenly develops around 12 wks
T/F: Stereopsis and depth acuity develops all at once in a kitten.
T/F: stereopsis in humans also occurs all at the same time
TRUE - ~6 weeks
humans: sort of.. have SUDDEN onset of stereopsis ~3mos, but tend to have CROSSED disparity appear about 1 wk before uncrossed (sometimes @ the same time) - ~14wks
Infants have a preference for (fusible/non-fusible) patterns prior to 3 mos of age (onset of binocularity)
NON-fusible preference before 3mos; then sudden onset of fusible preference
T/F: stereopsis and binocular fusion tend to be HIGHLY correlated.
–if true, what is this due to?
-does this occur in males or females first? Why?
TRUE - both develop SUDDENLY and @ the SAME TIME
- d/t development of OCULAR DOMINANCE COLUMNS in the VISUAL CORTEX (high order brain fxn)
- FEMALES first (~3 mos, not 5). Males have testosterone - limited by inhibitory interneurons
Does ocular alignment require convergence? Is convergence delayed by poor ocular alignment?
NO.
NO.
b/c @ 1 month (~6 wks, when eyes should be about ortho) eyes are either ortho or slight intermittent exo, so nml development will still occur.
Binocularity occurs in the cortex, but pupil constriction occurs in the _____, so early onset strabs (before 6 mos) have NO what?
SUBcortical areas
-early strabs have NO binocular pupillary response b/c binocularity hasn’t developed in the cortex
T/F: in a study, children WITH strabismus are not deprived of binocularity and binocular development is normal
-same study showed that a simple strabismus is NOT what causes amblyopia, rather it’s WHAT?
TRUE
-it’s CONSTANT fixation w/ one eye that does
T/F: Hyperacuity (Vernier acuity) develops at the same time as binocularity (which, again, is around what age?)
TRUE - ~12 wks, or 3-4 months of age.
Note: vernier STARTS out way worse than VA/grating acuity, then ends up being much better than VA b/w 3 mos and 3-4yrs
T/F: Vernier acuity has a SECOND phase in development where it gets waaaaaaayyyyy better than grating acuity (after the one that happened @ 3-4 months)
TRUE - at school age onset (4-5 Y/O) - one of the LATEST developing abilities
What’s the LAST change in visual development?
- two biggest problems that develop as a result?
- is this a function of BINOcular vision?
childhood CROWDING (5-9Y/O)
- 1) visual attention, 2) reading
- NO. Same results when monocular.
