Refractive development and prescribing in children Flashcards
what does prescribing =
management of refractive error
list 3 reasons why you would prescribe a refractive correction in adults
Manage ametropia
Symptoms
Occupational
Manage BV problems
list 3 reasons why you would prescribe a refractive correction in children
Manage ametropia
Symptoms?
Prevent amblyopia
To treat amblyopia
Manage BV problems
what 3 things will you consider/rule out before prescribing a refractive error for a child
No POH
FTND (full term normal delivery)
No FOH
BSV
what 4 questions do you want to ask yourself before you prescribe
Is refractive error within normal range for age?
Is emmetropization still taking place?
Will prescribing interfere with emmetropization?
Will level of refractive error cause amblyopia?
Will prescribing spectacles improve vision?
Will child adapt to their refractive correction?
what is the mean range of refractive error for a child 0-12 months of age
what type of refractive error are most of these infants found to have
how many of infants in this age group have anisometropia and of what D value
Large spread of refractive error
Mean cyclo refraction +2DS ± 2SD = -2 to +4 is normal
Most infants are hyperopic
Anisometropia >1.00DS = 31%
what is the prevalence of astigmatism that is normal for a child 0-12 months of age and what is the D value
which type of astigmatism is more common than in adults
by what age is astigmatism lost and how much of it is lost
Astigmatism >1.00DC = 67.8%
Significant WTR and ATR astigmatism more common than in adults
About two-thirds of astigmatism lost by 18 months
what happens to the spread of refractive error by the age of 6
what is the mean range of refractive error
by what age will astigmatism settle down by for a child ages 3-6 years old
which type of astigmatism is more common in later childhood
Very narrow spread of refractive errors
Mean +0.75DS to +1DS
Astigmatism may not stabilise till age 5
WTR astigmatism more common in later childhood than ATR
what is anisometropia
which age group of children is it more common in
what is the prevalence of anisometropia is this age group and of what D value
what 2 things is anisometropia commonly associated with
Interocular difference in refractive states between R and L eyes
More common in infants 0 to 3 years
Anisometropia >1.00DS = 31%
More commonly associated with:
- Hyperopic than myopic corrections
- Large refractive errors > +5.00DS or > - 6.00DS
what did the los angeles study discover about the worldwide prevalence of ametropia in children between age 6 months - 6 years old about:
Myopia
Hyperopia
Astigmatism
Myopia:
- values of anything over -0.50D was considered (so not high)
- if far less common than hyperopia
- but is more likely in asian children than white children
- myopia prevalence stable prevalence across age groups
Hyperopia:
- most common refractive error in both Asian and white children
but
- is more common in white children than in asian children (i.e. in east and south asian children)
- prevalence decreased after infancy and then increased again in older age groups
Astigmatism
- WTR astigmatism predominated at all ages
describe which types of ethnic children and environments myopia is more prevalent in and less prevalent in
More prevalent in:
Chinese children
Urban environments
Less prevalent in:
European children
Rural environments
which ethnic background had the highest prevalence of myopia living in the UK which was second and which was the lowest
what refractive error value did the account for
which age group did this account for
what was the ethnic difference largely accounted for
- South asian
- black
- white european
- -0.50D >
- age 10-11 years old
- largely accounted for by ethnic differences in axial length
in which age group is the prevalence of myopia higher
and therefore when will myopia in a child increase
higher in 12 y/o compared to 6-7 y/o
myopia will increase most likely as the child gets older
what is Emmetropization
Developmental process that co-ordinates growth of refractive component of eye
what is the two separate theories/processes of Emmetropization
Active
- Visual experience guides refractive state towards emmetropia
- Self-controlling – ability to recognise and correct imperfections
Passive
- Genetic control
- Pre-programmed
what are the 4 factors involved with genetics and emmetropisation
Twin studies
Myopia genes
Family history
Prevalence varies from country to country
what are the 6 factors involved with environment and emmetropisation
Increased near work Parental cigarette smoking Accommodative lag and variability Decreased time spent outdoors Urban environment Increased ambient lighting at night-time
between which ages does emmetropisation occur fast
and by when does it slow down for hyperopes and for myopes
Fast from 3 to 12 months
Age 2 years for hyperopes
Age 4 to 5 years for myopes
by what age is emmetropisation mostly complete
which types of children have faster changes
Mostly complete by 3 years of age
Faster changes in those with higher ametropia
how can you see whether emmetropisation has taken place in a child or if its still occurring
you monitor their refraction over a period of 4-6 months
which 3 types of patients will less likely emmetropise
Very high refractive error (> 5DS at 3 months)
Poor VA
ATR astigmatism
in which types of patients is emmetropisation less likely to be transient and what do you need to consider at this point
Anisometropia > 3DS less likely to be transient
Consider VA – amblyopia
what should you do when a child is going through emmetropisation to encourage the process to take place and how does this help
prescribe the full rx - as your giving a full stimulus
Some believe that while emmetropization is active, a partial correction should be prescribed (i.e. under-correction of the refractive error) to allow a stimulus for emmetropization…
However, evidence does not support this
what is a risk factor of amblyopia
Uncorrected high refractive error during first few years of life
