Cycloplegic Retinoscopy in Infancy

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Retinoscopy in infancy: cycloplegic versus non-cycloplegic C-18551 O/D

Yeotikar et al.2 evaluated the difference in refractive error in non-strabismic children between the ages of seven years and 16 years, using static retinoscopy

Fabrizio Bonci, Dip. Optom (ITA), MCOptom Luigi Lupelli, Dip. Optom (ITA), FAILAC, FIACLE, FBCLA The assessment of refractive status in very young children is often not conducted in the same manner as for adult patients. In particular, the child’s age, their cooperation and dynamic refractive status will be key factors which influence the accuracy of refraction. For this reason, it is often necessary to choose procedures which inhibit or minimise accommodative activity. This can be achieved by fogging with positive lenses or rousing the tonic (resting) accommodation (dry refraction), or with pharmacological agents (wet refraction). This review article compares the two approaches, focusing on the retinoscopy techniques.

under two conditions – first by fogging the contralateral eye with a positive lens and second with cycloplegia using cyclopentolate 1%. The study found that the average difference in refractive error between these two conditions was only 0.29DS more hypermetropic with cyclopentolate, highlighting the accurate results that can be obtained when there is adequate accommodative control

during

Furthermore,

static

Chan

retinoscopy.

and

Edward3

suggested a calculation which can be

Dry retinoscopy

to download a number of videoclips,

Static retinoscopy

especially

The patient views a distance target (four-

animations. Practitioners should also

six metres) so that accommodation is

consider not using a phoropter or trial

presumed to be static and in a relaxed

frame when conducting retinoscopy

condition. The fixating eye (contralateral

on a very young child, as this can be

to the one being examined) should be

intimidating for the child. It is preferable

adequately “fogged” with a positive lens

to use single trial lenses or a lens rack.

(resulting in an “against” movement seen

Speed during retinoscopy is essential

on the retinoscopy swipe).1 For children,

when performing this technique in

maintaining fixation at this distance

young

can be difficult and new computerised

maintain fixation only for very short

test charts generally provide dynamic

periods of time. In cases of fluctuation of

Mohindra retinoscopy

and more interesting targets to view

accommodation, the practitioner should

The Mohindra technique, also known

than a standard spotlight (Figure 1)

follow the “with” movement, ignoring the

as near retinoscopy or near monocular

to help with this. It is also possible

occasional “against” movements seen.

retinoscopy, carries the main advantage

cartoons,

children,

with

especially

different

as

they

used to match the dry retinoscopy result to that which would be obtained using cyclopentolate 1%, in children between 3.5 to five years of age. The astigmatic component is kept the same whilst the spherical component found in both meridians is multiplied by 1.45 and a value of 0.39D is added. However, this depends on an accurate static retinoscopy result having been obtained.

of being child-friendly and requiring less co-operation from the child.4 In this case, the stimulus is the dimmed light source of the retinoscope in a darkened room. The darkness of the room will facilitate the child to keep their attention on the retinoscope’s

light.

The

retinoscope

is held at a distance of 50cm (errors in distance are not clinically relevant), with hand-held trial lenses used to find

Figure 1 Examples of exciting targets presented by computerized test charts during retinoscopy. Different face expressions allow to the practitioner to talk to the child to maintain attention on the target (Courtesy of Thomson Software Solutions, UK).

49

the neutral point. The accommodation activity during the examination is small and the same in both eyes. It is important during the examination to keep the light of the retinoscope on the child’s pupil

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(to see the retinal reflex) for only a short

which can be uncomfortable, or even

period of time so as not to stimulate

distressing, for the child. This is notably

accommodation;

the

so because the acidic pH of the cycloplegic

optometrist’s attention should be focused

agent leads to stinging on instillation.

on the pupil, watching for maximum

Some practitioners advocate the use of a

dilation (indicating no accommodation).

5

local anaesthetic prior to instillation of

The procedure should be carried out

the cycloplegic agent; proxymetacaine

subsequently

with one eye occluded, preferably by the parent, while the other eye is evaluated. However, Wesson et al. confirmed that 6

there is no substantial difference in the result if binocular fixation is allowed (Figure 2); indeed this can be useful if the infant is resistant and becomes agitated

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with occlusion. Several people advocate neutralisation

of

the

two

principal

meridians of the eye separately, using loose spherical trial lenses. However, Saunders and Westall confirmed that 7

the accuracy of the technique can be improved using a combination of spherical and cylindrical lenses instead. Once the retinoscopy result is obtained, the refractive error was originally calculated by adding -1.25DS to the gross finding.

8,9

Saunders and Westall7 have reported that the accuracy can be improved if -0.75DS is added instead, for children aged between 0-2 years, and -1.00DS added for those children over two years of age. They also affirmed that the result achieved by the Mohindra procedure in children between six months and four years of age is similar to wet retinoscopy (using cyclopentolate 1% – see later), with a difference of only 0.50DS. Others have reported similar results,

10

and

certainly no differences greater than 1.00DS,

whilst similar results were

11

also obtained for children with Down’s syndrome

12

and

even

in

adults.

13

The Mohindra technique is useful for practitioners in Europe who are not permitted to used cycloplegic agents,

14

0.5% is the drug of choice as it stings less

Figure 2 Mohindra retinoscopy. Hand-held trial lenses are placed in front of both eyes whilst the child fixates the retinoscope light. The procedure should be run in darkened room (the high level of room light in this image was for photographic purposes only). accuracy of results will naturally depend on

the

practitioner’s

experience.16

Control of accommodation in children of pre-school age is more commonly achieved by pharmacological means, cycloplegic

agents

such

as

cyclopentolate and tropicamide; atropine can only be used by therapeutically qualified practitioners. All of these drugs are muscarinic receptor blockers, thus they work by blocking the muscarinic receptors in the ciliary body, which in A

turn

prevents

mydriatic

achieved

effect

by

accommodation. is

concurrently

inhibiting

muscarinic

stimulation of the iris sphincter muscle. An ideal cycloplegic would have no ocular and systemic adverse effects. Also, it should produce a rapid onset of cycloplegia, blocking accommodation completely

for

of

before

time,

an

accommodative studies

have

adequate

period

swiftly

restoring

ability.17

Several

reported

both

ocular

and systemic side effects (especially using atropine) in those children who have in

had

addition

a

cycloplegic to

this is not always recommended due to the risks associated with an anaesthetised cornea. To facilitate the application of

cycloplegics,

cyclopentolate

has

been instilled in spray form onto the eyelashes and the closed upper lid.19 Practitioners should also be conscious of their instillation technique, since different degrees of cycloplegia between

Cycloplegic agents

using

than other topical anaesthetics. However,

expected

refraction, mydriasis

the eyes can occur, especially if the child does not keep their eyes open wide enough and/or if there is significant postinstillation tearing (which is very likely). As such, practitioners can opt to instil the higher concentration of cycloplegic agent and/or instil further drops if regular review (eg, periodic measurement of the amplitude of accommodation) reveals differing levels of cycloplegia. Differences in the main cycloplegic agents are summarised in Table 1. The optometrist should select an appropriate agent considering factors such as the patient’s age and whether they have dark, or light coloured, irides. Adequate cycloplegic effect could be achieved with tropicamide in a teenage patient suspected of having latent hypermetropia, for

example,

whereas

cyclopentolate

is likely to be required for an infant suspected of having an accommodative esotropia. Those with light coloured irides may exhibit an increased response to

drugs

as

compared

with

darkly

pigmented irides, and therefore a lower

and cycloplegia, as detailed later.18

concentration/dose ought to be selected.

repeated use of cycloplegic agents.

Drug selection and instillation

be avoided in children with Down’s

One must remember, however, that the

Cycloplegia is an invasive technique

syndrome or those affected by cerebral

whilst there are benefits for conducting frequent follow-up assessments without 15

Overdose of cycloplegic agent has to

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palsy, trisomy 13 and 18, and other

Mydriasis

central nervous system (CNS) disorders.

Cycloplegia

Agent

Concentration Max effect

Recovery time

Max effect

Recovery time

Atropine

0.5-3.0%

1-2 hours

7-12 days

60-180 min

6-12 days

Cyclopentolate

0.5-2.0%

30-60 min.

1 days

25-75 min

6-12 hours

caused by LSD drugs.20,21 These reactions

Tropicamide

0.5-1.0%

20-40 min

6 hours

20-35 min

4-6 hours

generally occur within 20-30 minutes

Homatropine

2.0-5.0%

40-60 min.

1-3 days

30-60 min

1-3 days

Scopolamine

0.25%

20-30 min

3-7 days

30-60 min

3-7 days

these people, especially children, which causes

stimulation

of

the

medulla

and the cerebral centres, leading to hallucinogenic effects similar to those

after

administration.22

Tropicamide

1% should be considered in these children as opposed to cyclopentolate. Cyclopentolate Cyclopentolate

0.5%

or

1.0%

51

Table 1 Cycloplegic and mydriatic effects amongst the main cycloplegic drugs used in optometric practice

is

commonly used by practitioners as

(cycloplegia) at the 1% concentration.

the refractive examination. This drug is an

the cycloplegic agent of choice for

Although tropicamide is mostly used for

antagonist of the muscarinic acetylcholine

paediatric examinations. The cycloplegia

mydriasis, to examine the optical media

receptors, thus it dampens mediation of

achieved is not too deep, as compared

and the ocular fundus, several studies

the parasympathetic nervous system. As

with atropine, but it is quicker in

have suggested that this drug can be used

a result, systemic absorption of atropine

onset, often achieved after 30 minutes

for a cycloplegic effect.

In particular,

can lead to difficulties with swallowing

from its administration. Recovery of

it is a cycloplegic agent that can at least

food (opposed effects of the vagus nerve),

accommodation is typically between six-

detect latent hypermetropia, for example

inhibition of the salivary glands leading

12 hours after instillation whilst mydriasis

in school children, teenagers and those

to a dry mouth, and reduction of sweating.

resolves by 24 hours after instillation.

in their early 20s, with otherwise normal

Atropine can also increase firing of the

Although full cycloplegia is achieved

refractive status and/or with moderate

sino-atrial node (SA) and conduction

with atropine, the cycloplegic refractive

hypermetropia,

through the atrio-ventricular node (AV)

results obtained with cyclopentolate

during the post-natal period.

36

35

as well as for children 37

In adult

of the heart, leading to tachycardia. It

23

are comparable in “normals”,

high

patients undergoing refractive surgery, a

also

hypermetropic

and

also

study showed no significant difference

which can make breathing difficult.

in

between

Other side effects that have been reported

cyclopentolate

include dizziness, nausea and sensation

those

children24,25

children

with

strabismus.

26,27

cycloplegic

secretions,

tropicamide

months, it is advised that two drops of

1%.38 In the same patients, however,

of

cyclopentolate 0.5% are used as opposed

the study showed that cyclopentolate

reactions of the eyelids and conjunctiva.

to 1%. This is becasue drug absorption

was more effective than tropicamide

Atropine is able to pass through the

through the conjunctival epithelium and

in reducing accommodative amplitude

blood-cerebral-barrier and alter the state

skin is more rapid in infants compared

in adult myopes (near-point testing).

of consciousness of the child. Therefore,

to adults,

29,30

due to immature metabolic

and

bronchial

For children under the age of three

28

1%

refraction

decreases

being

unbalanced

and

allergic

in order to minimise the systemic Atropine sulphate

absorption of atropine, the practitioner

This is a natural alkaloid extracted

can gently press the punctum of both eyes

from the deadly nightshade (Atropa

and keep the patient’s head tilted back.

belladonna) plant. Its administration

A

is justified in children of pre-verbal

cycloplegic

psychosis and visual disturbances.

age or when other cycloplegic agents

2%

fail to produce a satisfactory level of

between the ages of four and 10 years by

Tropicamide

cycloplegia. Atropine is administrated

retinoscopy and automated refraction.

This is an anti-muscarinic drug with

three times a day during the three days

As expected, the study reported that

short-lasting

pupil

before the eye examination. Associated

homatropine produced a significantly

accommodation

mydriasis decreases in two weeks after

lesser cycloplegic effect than atropine,

enzyme systems in neonates and young children, which may prolong the effects of the drug.31,32 The main side effects of cyclopentolate include incoherent speech, hallucinations and disorientation, 33,34

(mydriasis)

effect and

on

on

the

recent

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and

study39 efficacy atropine

compared of 1%

the

homatropine in

children

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with residual accommodation being

anterior chamber (especially with

should remember that autorefractometry

greater

cyclopentolate)

and

vs.

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(1.80±0.40D

3.10±0.50D

with

with

atropine

videorefractometry,

although

useful as a guide and screening tool,

homatropine;

p