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OV3022 Binocular Vision, Paediatrics & Visual Impairment (PRD1 A 2021/22) > Refractive Development and Prescribing > Flashcards

Refractive Development and Prescribing Flashcards

1
Q

What is amblyogenic refractive error?

A

Refractive error that may lead to amblyopia

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2
Q

True or False- young children are unreliable px when carrying out subjective

A

True

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3
Q

True or False- Autorefractors are reliable for children

A

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)

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4
Q

What are the three different methods available for ascertaining refractive error using retinoscopy:

A

Static (or dry)
Mohindra technique
Cycloplegic refraction

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5
Q

What is static (dry) retinoscopy and how is it carried out?

A

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)

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6
Q

What are the cons of static retinoscopy for paeds?

A

•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

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7
Q

When do we do a cycloplegic refraction (i.e. a refraction with cycloplegic drops in the px)?

A
  • 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

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8
Q

What are the advantages of a cycloplegic refraction?

A

Advantages:

  • Reveals latent hyperopia
  • More accurate refraction
  • Aids fundus check as pupil is bigger for fundus photos, direct etc,
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9
Q

What are the disadvanatages of a cycloplegic refraction?

A

Disadvantages:

  • Photophobia
  • Distress
  • Temporary near vision problem ( although is this a problem for children that can’t read?)
  • Risk of adverse reaction
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10
Q

True or False- children with down’s syndrome have a decreased liklihood to an adverse reaction to cycloplegics

A

False

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11
Q

What two quantities of cyclopentolate are used and when?

A

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

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12
Q

How long does cyclopentolate take to come into full action?

A

10-55 MINs

(normally though around the 40 min mark)

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13
Q

If you aren’t convinced 1% cyclopentolate HCL is giving you adequate cycloplegia what options do you have?

A

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.

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14
Q

How do you instil cyclopnetolate drops in children?

A

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

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15
Q

How do you carry out mohindra retinoscopy technique?

A

•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)

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16
Q

What are the benefits of the mohindra technqiue?

A

It is carried out in total darkness so the light of the ret is the only thing to focus on which is quite useful

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17
Q

What are the cons of the mohindra technique?

A

Children can be quite afraid of the dark and clingy to their parents and so carrying out this technique realistically can be quite difficult

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18
Q

What age can we start doing subjective ret from?

A

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!
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19
Q

How can we check for accomodation in older children?

A
  • 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?
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20
Q

If a child px is being uncooperative with an RAF rule how else may you measure accomodation?

A

Dynamic retinscopy

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21
Q

How do you carry out dynamic retinoscopy?

A

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)

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22
Q

In theory, with dynamic ret, what should the practioner see at working distance?

A

A neutral reflex, however,

ØIn reality, small with movement observed

Ø+0.25 to +1.00DS lag is normal

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23
Q

True or False - refractive error is common amongst young children

A

True widespread of children 0-12 months are +2DS to -2DS

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24
Q

True or False- anisometropia is uncommon in young children 0-12 months

A

False - it is fairly common affecting around 31%

25
Q

Are most infants myopic or hyperopic?

A

Hyperopic

26
Q

What is emmetropization?

A

The act of refractive error sort of being corrected as a child grows

27
Q

When does emmetropization occur at its fastest rate?

A

ØFast from 3 to 12 months

ØThen slower period of change

  • bear in mind it happens fastest in children with high rates of ammetropia
28
Q

Is astigmatism over 1.00DC common in infants?

A

Yes affecting 67.8% of people

29
Q

Which form of astigmatism is more common in infants - WTR or ATR?

A

ØATR more common in infancy, and this decreases with age

ØWTR astigmatism more common in later childhood

30
Q

When is astigmatism lost in infants?

A

ØAbout two-thirds of astigmatism lost by 18 months

31
Q

When does astigmatism stabilise by?

A

•Astigmatism may not stabilise till age 5

32
Q

True or False - Although hyperopia in general is more common amongst infants, myopia is more prevalent in south asian children

A

True

33
Q

Why is myopia more prevalent in south asian children?

A

Ethnic prevalence is due to ethnic differences in axial length

34
Q

What are risk factors of myopia in children?

A
  1. Limited Outdoor activities
  2. High level Near work (in relation to outdoor activities)
  3. Levels of Education – higher years in education increases likelihood of myopia
  4. Parental myopia – family history
  5. Peripheral refraction
35
Q

What are the different ways in which we can prevent myopia?

A

•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

36
Q

True or False- some children may present with pathological hyperopia

A

False - there is no such thing as pathological hyperopia

37
Q

What features are characteristic of hyperopic eyes?

A

•Shallower vitreous and anterior chambers

optic nerve head drusen is not uncommon in highly hyperopic eyes

38
Q

Why can highly hyperopic children be confused with having a strabismus?

A

•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)

39
Q

What syndromes is hyperopia associated with?

A

Downs syndrome

40
Q

Why are downs syndrome children more likely to have hyperopia?

A

They tend to have slower emmetropisation processes and so are more likely to have hyperopia (but obviously can still be myopic).

41
Q

Is astigmatism common in downs syndrome children?

A

Yes - over 1.00DC astigmatism is present in around 55% of cases

42
Q

In what age group is anisometropia most common and how do we tackle it?

A

0-3 years

We need to keep monitoring it

43
Q

What is anisometropia in young children most commonly associated with?

A

•More commonly associated with

ØLarge refractive errors > +5.00DS or > - 6.00DS

ØWith myopia than hyperopia

ØPreterm infants especially those with ROP

44
Q

What effect does anisometropia have on BSV?

A

It causes reduced BSV

45
Q

True or False- anisomeropia can lead to amblyopia

A

True

46
Q

What is the link between astigmatism and amblyopia?

A

•Amblyopia risk > greater in children who are astigmatic between 6 and 24 months

ØRisk increases with increasing astigmatism

47
Q

What conditions are associated with high astigmatism?

A
  • Previous eye surgery
  • Previous corneal injury
  • Corneal dystrophies
  • Congenital cataract
  • Optic nerve hypoplasia
  • Retinitis pigmentosa
  • Albinism
  • Nystagmus
48
Q

What is the definition of emmetropization?

A

Developmental process that co-ordinates growth of refractive component of eye

49
Q

What are the two theories on how emmetropisation occurs?

A

1.Active:

ØVisual experience guides refractive state towards emmetropia

ØSelf-controlling – ability to recognise and correct imperfections

2.Passive:

ØGenetic control

Øpre-programmed

50
Q

By what age will majority of kids emmetropise?

A

By around 3 years of age

51
Q

When may emmetropisation be less likely to occur?

A

•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

52
Q

What level of refractive error causes amblyopia?

A

•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

53
Q

What strabismus is uncorrected hyperopia over 4 dioptres likely to cause?

A

An esotropia

54
Q

In terms of prescribing for 0-3 year olds when should we think about prescribing?

A

If values are equal to or greater than the values on the table - remember alongside prescribing we would have shorter recall periods.

55
Q

When would you prescribe irrespective of the guidelines?

A

When the px shows demonstrable amblyopia - so signs it is about to happen or is starting to happen.

Presence of heterotropia or significant phoria

56
Q

Will prescribing interfere with emmetropisation?

A

•Some believe that while emmetropization is active, under-correct the refractive error to allow a stimulus for emmetropization…

Evidence does not support this

57
Q

How should we be prescribing for ammetropia at school age ( so above 5/6 years of age)?

A

•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

58
Q

What are general considerations to bear in mind when prescribing children?

A
  • 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

59
Q
A

OV3022 Binocular Vision, Paediatrics & Visual Impairment (PRD1 A 2021/22) (4 decks)

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