paeds ophthal Flashcards
snellen acuity at birth
6/300
snellen acuity at 12 months
6/24
snellen acuity at 36 months
6/9-6/6
what age can start using snellen chart (6m) to test VA
4 yo and above
visual assessment in preverbal children
- fixation preference
- forced preferential looking (teller cards)
visual assessment in older children
- allen pictures
- kay pictures
- sheridan gardner matching test
- snellen
amblyopia (lazy eye) definition
Unilateral (or rarely bilateral) BOV due to disruption in normal visual development, caused by abnormal visual stimulation during sensitive period of visual development
VA criteria for amblyopia
- Unilateral amblyopia: difference in BCVA is 2 or more Snellen lines between 2 eyes
- Bilateral amblyopia: BCVA of 6/12 or less
pathophysiology of amblyopia
*Development of lateral geniculate nucleus and primary visual cortex is incomplete at birth and persists into postnatal period
*During critical period when there’s plasticity within visual system esp visual cortex, external factors can modify its development
causes of amblyopia
- strabismus (commonest)
- stimulus deprivation
- refractive error (anisometropia (2 eyes diff RE), ammetropia (both eyes deg high), astigmatism)
criteria for anisometropia
any of:
hyperopia > 1.5D
myopia > -3-4D
astigmatism > 1.5D
criteria for ammetropia
hyperopia >5D
myopia <-8D
criteria for astigmatism
> 2.5D
screening for amblyopia
- measure VA
- Holler test - child upset when good eye covered
principles of management for amblyopia
- provide clear retinal image
- correct ocular dominance
- parental counselling