03

Question 1

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)

Answer 1

EXOtropic

• KAPPA
• equal exo in each eye allows nml development
• 6 weeks (or ABOUT 1 month)

-20 diopters; always INTERMITTENT

Question 2

Which comes first: convergence/binocularity or ortho alignment?

Answer 2

unknown.

Question 3

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?

Answer 3

3-4 months
-accommodative convergence - present

-ocular DOMINANCE columns

Question 4

intermittent convergence occurs before 12 weeks (4 months) d/t what type of functional convergence?

Answer 4

accommodative

-convergence is absent @ 6 wks; suddenly develops around 12 wks

Question 5

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

Answer 5

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

Question 6

Infants have a preference for (fusible/non-fusible) patterns prior to 3 mos of age (onset of binocularity)

Answer 6

NON-fusible preference before 3mos; then sudden onset of fusible preference

Question 7

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?

Answer 7

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

Question 8

Does ocular alignment require convergence? Is convergence delayed by poor ocular alignment?

Answer 8

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.

Question 9

Binocularity occurs in the cortex, but pupil constriction occurs in the _____, so early onset strabs (before 6 mos) have NO what?

Answer 9

SUBcortical areas

-early strabs have NO binocular pupillary response b/c binocularity hasn’t developed in the cortex

Question 10

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?

Answer 10

TRUE

-it’s CONSTANT fixation w/ one eye that does

Question 11

T/F: Hyperacuity (Vernier acuity) develops at the same time as binocularity (which, again, is around what age?)

Answer 11

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

Question 12

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)

Answer 12

TRUE - at school age onset (4-5 Y/O) - one of the LATEST developing abilities

Question 13

What’s the LAST change in visual development?

• two biggest problems that develop as a result?
• is this a function of BINOcular vision?

Answer 13

childhood CROWDING (5-9Y/O)

• 1) visual attention, 2) reading
• NO. Same results when monocular.