Refractive Development and Prescribing Flashcards
What is amblyogenic refractive error?
Refractive error that may lead to amblyopia
True or False- young children are unreliable px when carrying out subjective
True
True or False- Autorefractors are reliable for children
False - on un-cylopleged children (i.e. children who’s accommodation has not been blocked) autos are very unreliable.
(This is not the case for children who have been given cyclo drops)
What are the three different methods available for ascertaining refractive error using retinoscopy:
Static (or dry)
Mohindra technique
Cycloplegic refraction
What is static (dry) retinoscopy and how is it carried out?
Static = static accommodation i.e. relaxed
This is done by Using a distance fixation target…
Needs to be quick
Can be done awake or asleep
Bell’s phenomenon may be a problem if asleep
May need to use a Children’s trial frame as adult ones are too big
Hold lenses in front of both eyes
ØNeutralise each meridian separately
•50cm working distance may be more appropriate only because you have to hold up the lenses.
ØMake adjustment for working distance
(you are still fogging contralateral eye)
What are the cons of static retinoscopy for paeds?
•Non-cycloplegic static retinoscopy far less reliable in very young paediatric subjects
•
•Tends to result in spherical error more negative i.e. less positive (by up to 4DS)
ØThis can occur into teenage years
When do we do a cycloplegic refraction (i.e. a refraction with cycloplegic drops in the px)?
- Desirable in all new cases
- Essential in:
ØReduced V/VA
ØReduced stereopsis
ØSuspect or manifest strabismus
ØLarge, decompensating SOP – when looking for high plus
ØFH strabismus or high hypermetropia
ØSuspected pseudomyopia
ØAnisometropia ≥1D
ØPoor accommodation
What are the advantages of a cycloplegic refraction?
Advantages:
- Reveals latent hyperopia
- More accurate refraction
- Aids fundus check as pupil is bigger for fundus photos, direct etc,
What are the disadvanatages of a cycloplegic refraction?
Disadvantages:
- Photophobia
- Distress
- Temporary near vision problem ( although is this a problem for children that can’t read?)
- Risk of adverse reaction
True or False- children with down’s syndrome have a decreased liklihood to an adverse reaction to cycloplegics
False
What two quantities of cyclopentolate are used and when?
Cyclopentolate HCL 0.5% - FOR under 6 MONTHS and over 12 years ( so that near reading is not too badly affected)
Cyclopentolate HCL 1% - FOR over 6 MONTHS
There may
How long does cyclopentolate take to come into full action?
10-55 MINs
(normally though around the 40 min mark)
If you aren’t convinced 1% cyclopentolate HCL is giving you adequate cycloplegia what options do you have?
In hospital they may use 1% cyclopentolate HCL with 1% tropicamide. This would be for a very young child with very dark irides.
1% atropine may be used - this would be used if a child whos very young with dark irides has a large manifest strabismus.
How do you instil cyclopnetolate drops in children?
Instillation of Cyclopentolate HCL drops:
•
- Drop onto lashes of closed eye
- Use atomiser (availability limited)
- Some use Proxymetacaine HCL 0.5% first
ØPrevents stinging but child may object to cyclo drop
ØIncreases absorption
How do you carry out mohindra retinoscopy technique?
•Also called near (monocular) retinoscopy
ØOn one eye at a time (occlude one eye)
•
- Carried out in a totally dark room
- Light of ret used as fixation target
ØAssumes eye is in normal resting state
•50cm working distance however instead of subtracting 2DS for your working distance with the mohindra technqiue you only subtract 1.25DS from findings (allowing for 0.75DS accommodation)
What are the benefits of the mohindra technqiue?
It is carried out in total darkness so the light of the ret is the only thing to focus on which is quite useful
What are the cons of the mohindra technique?
Children can be quite afraid of the dark and clingy to their parents and so carrying out this technique realistically can be quite difficult
What age can we start doing subjective ret from?
In general….
- Don’t attempt if child < 5 years?
- Age 5-7 years:
ØSubjective responses variable
ØPlace little reliance upon them
ØRemember to use 1.00Ds blur test
- Age 8+ years rely more on subjective
- Don’t forget children aim to please!
How can we check for accomodation in older children?
- In older children
- Check N5 acuity at 5cm
- Use budgie stick or RAF rule
- Push-up method
- Only thing to bear in mind is that it requires subjective response – which could be unreliable based on child?
If a child px is being uncooperative with an RAF rule how else may you measure accomodation?
Dynamic retinscopy
How do you carry out dynamic retinoscopy?
Target: Near target at subjects working distance. (Near target is either held in patients hand or A scale containing a self-illuminated cube with pictures held as shown in figure 1)
The patient sees the target binocularly
Patients must wear their distance correction
Retinoscope is kept alongside the target and the movement of the reflex is observed
If the movement is against, then the subject is over accommodating. Move the retinoscope towards the kid till you get neutral point while keeping target fixed. The distance between the neutral point and the target will be converted into dioptres.The resultant dioptric value is the magnitude of the lead of the accommodation.
If the movement is with, then the subject is under accommodating. Move the retinoscope away from the kid till you get neutral point while keeping target fixed. the distance between the neutral point and the target will be converted into dioptres. The resultant dioptric value is the magnitude of the lag of the accommodation.
(equally you can pop lenses infront of the eye rather than moving the ret)
In theory, with dynamic ret, what should the practioner see at working distance?
A neutral reflex, however,
ØIn reality, small with movement observed
Ø+0.25 to +1.00DS lag is normal
True or False - refractive error is common amongst young children
True widespread of children 0-12 months are +2DS to -2DS
True or False- anisometropia is uncommon in young children 0-12 months
False - it is fairly common affecting around 31%
Are most infants myopic or hyperopic?
Hyperopic
What is emmetropization?
The act of refractive error sort of being corrected as a child grows
When does emmetropization occur at its fastest rate?
ØFast from 3 to 12 months
ØThen slower period of change
- bear in mind it happens fastest in children with high rates of ammetropia
Is astigmatism over 1.00DC common in infants?
Yes affecting 67.8% of people
Which form of astigmatism is more common in infants - WTR or ATR?
ØATR more common in infancy, and this decreases with age
ØWTR astigmatism more common in later childhood
When is astigmatism lost in infants?
ØAbout two-thirds of astigmatism lost by 18 months
When does astigmatism stabilise by?
•Astigmatism may not stabilise till age 5
True or False - Although hyperopia in general is more common amongst infants, myopia is more prevalent in south asian children
True
Why is myopia more prevalent in south asian children?
Ethnic prevalence is due to ethnic differences in axial length
What are risk factors of myopia in children?
- Limited Outdoor activities
- High level Near work (in relation to outdoor activities)
- Levels of Education – higher years in education increases likelihood of myopia
- Parental myopia – family history
- Peripheral refraction
What are the different ways in which we can prevent myopia?
•Atropine
Øto paralyse accommodation
•Bifocals and multifocals
Øto reduce accommodation at near
•Contact lenses
ØTo flatten cornea or retard axial elongation
ØOrthokeratology
- Under-correction
- Diet
- Outdoor activities
- Sunlight
BEAR IN MIND AT PRESENT THERE IS NO DEFINITIVE ANSWER
True or False- some children may present with pathological hyperopia
False - there is no such thing as pathological hyperopia
What features are characteristic of hyperopic eyes?
•Shallower vitreous and anterior chambers
optic nerve head drusen is not uncommon in highly hyperopic eyes
Why can highly hyperopic children be confused with having a strabismus?
•Large positive angle kappa in highly hyperopic eyes gives appearance of divergent strabismus
(thats why we don;t base diagnosis on a single test as here corneal reflections would be totally out)
What syndromes is hyperopia associated with?
Downs syndrome
Why are downs syndrome children more likely to have hyperopia?
They tend to have slower emmetropisation processes and so are more likely to have hyperopia (but obviously can still be myopic).
Is astigmatism common in downs syndrome children?
Yes - over 1.00DC astigmatism is present in around 55% of cases
In what age group is anisometropia most common and how do we tackle it?
0-3 years
We need to keep monitoring it
What is anisometropia in young children most commonly associated with?
•More commonly associated with
ØLarge refractive errors > +5.00DS or > - 6.00DS
ØWith myopia than hyperopia
ØPreterm infants especially those with ROP
What effect does anisometropia have on BSV?
It causes reduced BSV
True or False- anisomeropia can lead to amblyopia
True
What is the link between astigmatism and amblyopia?
•Amblyopia risk > greater in children who are astigmatic between 6 and 24 months
ØRisk increases with increasing astigmatism
What conditions are associated with high astigmatism?
- Previous eye surgery
- Previous corneal injury
- Corneal dystrophies
- Congenital cataract
- Optic nerve hypoplasia
- Retinitis pigmentosa
- Albinism
- Nystagmus
What is the definition of emmetropization?
Developmental process that co-ordinates growth of refractive component of eye
What are the two theories on how emmetropisation occurs?
1.Active:
ØVisual experience guides refractive state towards emmetropia
ØSelf-controlling – ability to recognise and correct imperfections
2.Passive:
ØGenetic control
Øpre-programmed
By what age will majority of kids emmetropise?
By around 3 years of age
When may emmetropisation be less likely to occur?
•Less likely if:
ØVery high refractive error (> 5DS at 3 months)
ØVery Poor VA
ØHigh level of ATR astigmatism
Also if high level of anisometropia
What level of refractive error causes amblyopia?
•Uncorrected high refractive error during first few years of life is a risk factor for amblyopia:
Ø> 3.50DS (in one meridian) in 1 year olds
Ø> 2.00DS (in one meridian) in 4 year olds
ØIf refractive error increasing in +
ØIf refractive error not changing from 1-4 years this is also a risk factor
What strabismus is uncorrected hyperopia over 4 dioptres likely to cause?
An esotropia
In terms of prescribing for 0-3 year olds when should we think about prescribing?
If values are equal to or greater than the values on the table - remember alongside prescribing we would have shorter recall periods.
When would you prescribe irrespective of the guidelines?
When the px shows demonstrable amblyopia - so signs it is about to happen or is starting to happen.
Presence of heterotropia or significant phoria
Will prescribing interfere with emmetropisation?
•Some believe that while emmetropization is active, under-correct the refractive error to allow a stimulus for emmetropization…
Evidence does not support this
How should we be prescribing for ammetropia at school age ( so above 5/6 years of age)?
•Myopia:
ØFull correction of myopia
ØNo evidence that under- or partial correction reduces myopia progression
•Hyperopia:
ØUncorrected hyperopia >+1.50DS can impact VA
ØLittle solid evidence of benefit of correcting small refractive errors (up to +1.50DS, or astigmatism up to 1DC)
•Astigmatism:
ØCorrect astigmatism >2DC
•Anisometropia
ØCorrect anisometropia of >1.50D hyperopia, >2.00D myopia
What are general considerations to bear in mind when prescribing children?
- Children are usually asymptomatic
- So Not always an easy decision
- Ideally we want to:
Øprevent amblyopia
Ø but not halt emmetropization
Ø yet encourage binocularity
•Decision can be borderline
ØMonitor closely - have short recall periods
ØWill parents comply?- this may be a big factor in your decision
