Week 2.08 Developmental BV Flashcards
Define stereopsis
Awareness of the relative distances of objects from the observer by means of binocular vision only and based on retinal image disparity
What is partial decussation
Crossing of fibres from re to L side of brain
In humans there is partial decussation 50% of fibres cross
Do visual field overlap at birth
Yes they do however tonic convergence is low so physiological position are 15 to 20 degrees divergent
Fixational eye movements
There is monocular fixation within 1 degree of some unspecified area in children 2 weeks old to 1 year
Full development is slow: monocular fixation in 10 year olds less accurate than in adults
Versional eye movements
Conjugate eye movements evident in all direction during 1st 48hrs of life
Saccades evident in neonates
Short pursuit eye movements can be elicited in neonates - develop slowly take ~6months
Reflex eye movements
Unconditioned: present at birth – genetically transmitted
Conditioned: require visual experience to develop - not present at birth or immature at birth
VOR
Fully functional at birth
Higher in amp and velocity than in later life
Movements due to head movements
Opto kinetic reflex
Can investigate this by subject placed inside a rotating drum with stripes following the eye movements with electrodes that are placed on scalp
Normal OKN at 4 months
Onset of binocularity also 4 months
What are pupillary responses like in newborns
In newborns, pupillary responses exhibit prolonged latencies & smaller amplitude relative to adults (present but sluggish)
Resting pupil diameter increases during 1st two months of life
For stereopsis u must have?
Simultaneous perception
Fusion
When does stereopsis develop
3-5 months of age
Males or females develop stereopsis faster?
Females
