Aetiology of Amblyopia Flashcards
what is the critical period for visual development
7-8 yrs
what is the sensitive period
time of deprivation to teen age years
why is the brain vulnerable
neural plasticity
when is amblyopia thought to start
when baby is binocular (2-4 months)
does the age of the px affect the response to treatment
yes - the younger the px the more rapid the improvement
why does the age matter in relation to response of treatment
due to the neural plasticity
what is the exception of treatment beyond age 8
anisometropic amblyopia or those with no previous treatment
what else can amblyopia affect
What are the two mechanisms for amblyopia
deprivation of form vision - passive element and abnormal binocular interaction or competition - active/dynamic element
what did Hubel and Wiesel (1965) do to test effects of strabismus
on cats - surgically induced or lid suturing to prevent BSV - have an abnormally high proportion of monocular cells at the visual cortex where there should be binocular cells
when are children most sensitive to amblyopia
0-3 yrs old
when does the sensitivity to amblyopia decrease
until 7yrs old
what do the X and Y cells do
send responses to the brain
where is our best vision in the eye
fovea
what do X cells do
respond to sustained stimulation (stable images, well focused images)
where are X cells most dense
fovea
what are X cells poor at
spatial resolution and detecting contrast
How many layers in the LGB
6 layers
does deficit in the LGN have an effect on amblyopia
yes makes it more dense
what are ocular dominance columms
columnar arrangement of the cells in the striate cortex
how much does 1D affect the response in cells
reduced affect in one cell
how many D is a risk factor for child aged 1
3D - would mean they are likely to have this for the rest of their life.
is amblyopia a genetic condition?
No but the amblyogenic factors are genetic
what is the definition of amblyopia
a reduction in visual acuity secondary to neurological deficits in visual output but abnormal brain stimulation during critical periods of visual development.
what is the prevalence of amblyopia
1-5%
what is the most common cause of vision loss in infants and young children
amblyopia
true of false the prevalence of amblyopia is higher in lower socioeconomic classes
true
what are the 7 functional types of amblyopia
stimulus deprivation, strabismic, anisometropic, ametropic, meridional, idiopathic, hysterical/psychogenic
what is the type of organic amblyopia
toxic
can improvement be expected from functional amblyopia treatment
yes
what is organic (toxic) amblyopia
no lesion detectable, can be reversible or irreversible, consider if no response to treatment.
