When are eyes most susceptible to teratogens during development?
During the 4th week as eyes begin to form around day 22
Teratogen we are most worried about is alcohol
What are the three stages during pregnancy?
-Germinal period (day 1-21, first 3 weeks)
-Embryonic period (weeks 4-8) when the eyes are most susceptible to teratogens
-Fetal period (9 weeks to birth)
What are the most mature eye movements at birth?
Saccades
Infants use small saccade steps rather than a single large saccade
When are pursuits developed?
As early as 1-4 weeks
At this time, velocity significantly lags behind the stimulus and infants use frequent saccades to catch up to the stimulus
When do pupillary responses to light develop?
Present at birth in both full term and premature infants
When does accommodation develop?
Present at birth in both full term and premature infants
Duration of full term pregnancy vs preterm
Full term is 39-40 weeks
Preterm is commonly < 32-37 weeks (could be less)
Are most neonates relatively eso or exo?
Most have a relatively larger nasal reflex on Hirschberg (+) which makes them appear exo
When does convergence/divergence develop?
As early as 1 month (static target 10-20 inches away)
When are accommodation and vergence typically stable in an infant/child?
2 months
When should the eyes be completely aligned by?
3-4 months
May have intermittent strabismus in the first 3 months but it should normalize
Critical period for stereopsis development
3 months
When does onset or fusion of stereopsis occur?
Between 3-5 months
Visual acuity expected in a 6 month year old
20/100 using Teller Cards
Technically, an infant can achieve 20/20 acuity on VEP
When are adult levels of NPC reached?
6 months
When are accurate pursuits of a moving target expected (accomplished by equal head and eye movements)
6 months
What is the timeline for onset of infantile esotropia?
Before 6 months of age
Acuities expected by 12 months using Teller
20/40 to 20/50
When does stereopsis begin to reach adult levels?
Begins to reach adult levels at 2 years but continues to improve with age
The fovea is not fully mature until when?
2-3 years of age
-Structures of visual pathway not fully myelinated until this time
-In additional the inner layers of the retina are still displacing outwards
-Cortex is also maturing
When can the first foveal light reflex be observed?
2-3 months
When can you start to assess stereoacuity with the LANG test?
6 months
Expected BCVA for a 3 year old (using Teller or Lea)
20/30
When can you begin testing worth 4 dot?
4 years old
