cycloplegic refraction in optometric practice 1337594763401 2

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Optometry in Practice Vol 6 (2005) 107120

2005 The College of Optometrists

Introduction

Although new methods of refraction have been developed

over the years, cycloplegic refraction has remained a time-

tested, reliable and valid procedure for obtaining refraction

data. In non-communicative or uncooperative patients,those with functional visual problems or whose visual

acuity (VA) cannot be corrected to an expected level,

cycloplegia is often essential for an accurate assessment of

refractive error. Also, cycloplegia is often necessary in

patients with inconsistent responses or symptoms, and in

patients with media opacities or aberrations (Amos 2001).

Without cycloplegia, determining the refractive status of

young patients with accommodative esotropia,

pseudomyopia or latent hyperopia would be much more

difficult.

An ideal cycloplegic would have no ocular or systemic side

effects; it would be able to produce a rapid onset ofcycloplegia, inhibit accommodation completely for an

adequate period of time and then swiftly restore effective

accommodation. It would also have the capacity for safe

administration in general practice by appropriately

qualified personnel. There is no single cycloplegic drug that

covers all these requirements (Amos 2001), but some

agents do satisfactorily achieve the desired clinical result

with minimum disadvantages.

Here we review drug mechanisms, instillation techniques

and the uses and adverse reactions of common drugs that

can be used in cycloplegic refraction.

Method of Literature Search

Pertinent articles on cycloplegic drugs published in peer-

reviewed journals were identified through a multistaged,

systematic approach. In the first stage, a computerised

search of the PubMed database (National Library of

Medicine) was performed to identify all articles about

cycloplegic drugs published up to March 2005. The terms

cycloplegics, cycloplegia, paediatric and pediatric,

cyclopentolate, atropine, homatropine and tropicamide

were used for a broad search. In the second stage all

abstracts were examined to identify articles pertinent to

our review. Copies of the entire articles were obtained.

Bibliographies of the articles retrieved were manually

searched using the same search guidelines. Key textbooks

were also searched. In the third stage, articles werereviewed and information relating to the use of cycloplegic

drugs in optometric practice was incorporated into the

manuscript.

Drug Mechanism

Cycloplegic drugs block the actions of the parasympathetic

nervous system. Pharmacologically they are known as

antimuscarinics, anticholinergics, cholinergic antagonists,

muscarinic antagonists, parasympathetic antagonists or

parasympatholytics. The muscarinic receptors are

normally stimulated by the release of acetylcholine fromthe nerve endings of the parasympathetic system. When

stimulated, the ciliary muscle contracts, pulling the ciliary

body forward. This relieves the tension in the suspensory

ligaments, which support the lens. Consequently, the lens

becomes more convex, which results in an increase in

refractive power to produce accommodation. During

cycloplegia, when the receptors of the ciliary muscle are

blocked they are no longer receptive to acetylcholine and

accommodation is not possible (Bloom 1998, Titcomb

2003, Viner 2004). The end result is that the contraction of

the ciliary muscle is blocked and the iris sphincter muscle

is relaxed, resulting in cycloplegia and mydriasis.

Instillation Techniques

Pre-instillation assessment

Before any cycloplegic agent is administered, a satisfactory

pre-instillation ocular evaluation should be performed.

This practice not only protects the practitioner legally but

also gives valuable information on potential

contraindications to the intended cycloplegic as well as

obtaining baseline clinical information that may not be

Cycloplegic Refraction in OptometricPracticeFrank Eperjesi PhD and Karen Jones BSc

Division of Optometry, School of Life and Health Sciences, Aston University, Birmingham

Date of acceptance 29 July 2005

Address for correspondence: Dr F Eperjesi, Division of Optometry, School of Life and Health Sciences, Aston University, Aston Triangle,Birmingham, UK


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F Eperjesi & K Jones

obtainable under cycloplegia. The following informationcould be taken before drug instillation:

a full and detailed history, including visual, general

medical, allergy, drug and family history

distance and near VA

pupillary reflexes

refraction

slit-lamp examination, paying particular attention to

anterior angle configuration

tonometry, where the patient might be at risk of closure

of the anterior chamber angle

Obtaining patient or parental consent before administering

any cycloplegic drug is recommended (Bartlett 1978); thiscould be in the form of a verbal consent followed by an

appropriate entry in the patient records or a more formal

signed consent form. The College of Optometrists provides

information sheets on the instillation of cycloplegic

drugs (www.college-optometrists.org/professional/

cyclopentolate.htm and www.college-optometrists.org/

professional/tropicamide.htm) and these could easily be

adapted into a consent form.

Drop instillation

The procedure for instilling topical medication into the eye

consists essentially of inclining the head backwards so thatthe optical axis is as nearly vertical as possible. The lower

lid is then retracted, and the upper lid held back with the

thumb or forefinger. Patients should then be asked to look

over their head in order to move the cornea away from the

instillation site to minimise the blink reflex. The drop

should then be instilled into the lower conjunctival sac,

keeping the bottle tip away from the globe to avoid contact

contamination. The lids can then be gently closed and the

head brought forward. Children can become very

distressed during this procedure; the level of distress can

sometimes be minimised by careful explanation of the

instillation process.

Use of anaesthetics

The most commonly used cycloplegic is cyclopentolate 1%

(see below). Because it is unstable at neutral pH,

preparations are acidified with dilute hydrochloric acid to

around pH 4 and this leads to stinging on instillation

(Sutherland & Young 2001). It has been suggested that

instilling a local anaesthetic before a cycloplegic agent can

lead to more successful and less stressful drug instillation

(Leat et al. 1999). The topical local anaesthetic

proxymetacaine 0.5% stings considerably less than other

anaesthetics, takes less than 30 seconds to anaesthetise

the eye (Boozan & Cohen 1953) and the anaesthetic effect

lasts for 1025 minutes (Havener 1983). Therefore,proxymetacaine 0.5% is becoming the anaesthetic of

choice (Leat et al. 1999, Shah et al. 1997, Sutherland &

Young 2001), despite the fact that it is also acidified with

hydrochloric acid to a similar pH as cyclopentolate and can

cause discomfort.

The reasons for instilling a topical local anaesthetic before

the cycloplegic are twofold. Firstly, if the cornea is

anaesthetised, the stinging, irritation and lacrimation due

to the second drop, the cycloplegic, will be diminished

(Shahet al. 1997); this is particularly useful if more than

one drop of cyclopentolate is required. In a group of 29

adult subjects there was a highly statistically significant

reduction in total discomfort with cyclopentolate instilledafter premedication with proxymetacaine compared with

the use of cyclopentolate instilled after a placebo

(Sutherland & Young 2001). Secondly, the local

anaesthetic may increase the absorption of the cycloplegic

agent (Viner 2004). The disadvantage of this technique in

a paediatric population is that if the child is adverse to the

first set of drops, he or she may make it extremely difficult

for the second, more important drugs to be instilled

(Bartlett 1978, Leat et al. 1999, Viner 2004).

Proxymetacaine 0.5% should be used with caution as it

may cause epithelial and stromal keratitis if used

repeatedly over a period of a few hours (Doughty & Field

2005).

Spray instillation

Ismailet al. (1994) found that spraying cyclopentolate on

to the eyelashes of a gently closed upper lid resulted in an

easier application with no compromise to the cycloplegic

effects. Goodman et al. (1999) also tested a spray

instillation technique and found that patient discomfort

associated with the spray was slightly greater that that of

eye drops but this was not clinically significant.

Paradoxically, the spray was better received by the

parents.

Dosage

The dosage for all cycloplegics should be the minimal

concentration that will achieve the clinical task

satisfactorily. To overmedicate when maximum cycloplegia

has been reached increases the probability of systemic

absorption and therefore intensifies the side effects. In

other words, using several drops of a cycloplegic when one

drop is sufficient is poor practice (Amos 1978). As with all

ocular drugs, the chances of systemic side effects can be

reduced by occluding the eyelid puncta for a few seconds

after drug instillation (Chang 1978, Viner 2004), although

this is not always possible with children.


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Cycloplegic Refraction in Optometric Practice

Degree of cycloplegia

After the cycloplegic has been instilled and the time limit

for maximum cycloplegia has been reached (see below),

the optometrist must then decide whether the degree of

cycloplegia is adequate to permit a reliable refraction.

Mydriasis is not necessarily a good indicator of when full

cycloplegia has taken place; therefore it is best to check for

cycloplegia by looking at the reflex with a retinoscope. If

cycloplegia is complete, a non-fluctuating retinoscopy

reflex is observed. If accommodation is active, then

fluctuation of the retinoscopy reflex will be seen. If

fluctuation is present, there are two options: use another

drop of cyclopentolate, or wait for a few more minutes and

check the retinoscopy reflex again (Moore 1997). Another

way of assessing monocular residual accommodation

would be to obtain a subjective response on the clarity of a

near-text target, although in many children performing this

type of check test is impossible.

Types of Cycloplegic Drugs

Cyclopentolate

Cyclopentolate is a synthetically derived antimuscarinic

and is formulated as a hydrochloride salt solution. It is

classified as a prescription-only medicine (POM) that canbe used and supplied by an optometrist provided it is in the

course of professional practice and in an emergency

(exemption level 1).

Cyclopentolate should be instilled 3040 minutes before

refraction (Moore 1997) and a further drop can follow after

515 minutes if necessary, particularly in patients with

heavily pigmented irises. It rapidly produces cycloplegia of

short duration with maximum cycloplegia after 1560

minutes (longer onset in dark pigmented irises) and the

effects last between 8 and 24 hours (Ansons & Davis 2001,

Chang 1978, Moore 1997, Titcomb 2003). This drug seems

to be the eye care professionals drug of choice for

cycloplegic refraction (Ansons & Davis 2001, Shah et al.1997), probably because of its rapid action and minimal

side effects. It is considered to be highly effective in most

cases provided retinoscopy is timed to coincide with its

maximum action. Cyclopentolate is available in 0.5% and

1% strengths in Minim form and in 2% strength in a dropper

bottle form, although this dosage is not routinely used as it

is very likely to result in side effects. To reduce the chances

of systemic effects, patients under 1 year old should

receive the 0.5% formulation (Mehta 1999, Scheimanet al.1997). All forms should be kept between 2C and 8C.

Cyclopentolate is structurally different to atropine (see

below) and can therefore be used when a patient has an

atropine allergy. Instilling three drops of 1% cyclopentolate10 minutes apart produces retinoscopy values comparable

to those obtained when children are atropinised for 3 days;

using more than three drops in one session increases the

chances of side effects (Moore 1997).

Cyclopentolate does not produce complete cycloplegia, but

leaves a residual amount of accommodation of about 1.50D

or less (Leatet al. 1999). However, this depth of cycloplegia

is adequate for most cases and also means that a tonus

allowance does not normally need to be considered when

calculating the final prescription (Viner 2004). It has been

reported that if residual accommodation exceeds 2.00D,

cycloplegic refraction may be unreliable and inaccurate

(Amos 2001). One randomised masked study reported that1% cyclopentolate produced adequate cycloplegia in a

group of 313-year-olds (Goodmanet al. 1999).

Atropine

Atropine sulphate is a solanaceous alkaloid derived from

Atropa belladonna. Atropine has been known since biblical

times. It is an organic ester of tropic acid and tropine and

is the most potent of the antimuscarinic drugs (Titcomb

2003). It is classified as a POM, while changes to the range

of medicines that can be sold, supplied or administered by

optometrists have classified atropine in exemption level 2.

This means that atropine is only accessible to optometristswho have undergone appropriate additional training and

are accredited by the General Optical Council.

Atropine is rarely used in optometric practice. It has a slow

action and a duration of 12 weeks. Atropines length of

action completely rules out its use in infants under the age

of 3 months because of the risk of stimulus deprivation

amblyopia and it is associated with a significant number of

possible side effects in children (Viner 2004). Its use now

seems to be mainly confined to the Hospital Eye Service

and a few specialised optometry practices. It is available in

the form of 0.5% or 1% drops or ointment. The ointment

form provides longer drug contact time with less systemic

absorption than drops but, like most ocular ointments,often causes smeary vision and has the added disadvantage

of being more likely to cause contact dermatitis and

inhibition of corneal epithelial mitosis (Rengstorff &

Doughty 1982). It should be stored between 8C and 25C.

To reduce the likelihood of systemic effects, patients

younger than 12 months should receive the 0.5%

formulation (Mehta 1999). Atropine 0.5% is recommended

in lightly pigmented irises while atropine 1% is indicated in

the refraction of children with darkly pigmented irises,

those with a constant strabismus with a suspected

accommodative element or when cyclopentolate has

proved to be ineffective (Ansons & Davis 2001, Moore


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1997). Interestingly, Rosenbaum et al. (1981) found thatatropine revealed a mean difference of only 0.34D more

hypermetropia than cyclopentolate in a sample of

esotropic Caucasian children.

When using atropine for refraction in children under 30

months, it is recommended that one drop of 0.5% atropine

is instilled three times a day for 3 days before refraction

and once more on the morning of the refraction. For

refractions in children between 30 months and 5 years,

one drop of 1.0% atropine is instilled three times a day for

3 days and then once on the morning of the refraction

(Ansons & Davis 2001). When using the ointment,

however, it is not usually instilled on the day of the

examination because it takes about 2 hours for theointment to dissipate and even a thin layer of unabsorbed

ointment may interfere with the refractive procedures

(Ansons & Davis 2001). The instillation (three times a day

for 3 days) is done at home and is probably excessive, as

maximum cycloplegia is achieved by the second day. This

does however allow for missed instillations and also

ensures effective relaxation of accommodation in even the

most resistant eyes (Amos 1978, Bartlett 1978, Chang

1978). The use of atropine also generally requires a tonus

allowance of about 1.00DS to be made to the final

prescription, because atropine completely abolishes all

accommodative tonus, and when the cycloplegic effects

wear off, if no allowance is made, the resultant prescriptionwill be over-plussed.

Homatropine

Homatropine hydrobromide is a semisynthetic alkaloid

formed by combining mandelic acid with tropine. It is a

POM and has also been classified as an exemption level 2

drug. It is not as potent as atropine and does not last as

long, although it does last slightly longer than

cyclopentolate. It should also be stored between 8C and

25C. For homatropine to produce satisfactory cycloplegia,

one drop of 2% homatropine is required every 10 minutes

up to a total of three drops or one drop of 1% homatropine

every 10 minutes for an hour (Chang 1978). Maximumcycloplegia occurs in 3060 minutes and may last 12 days

(Chang 1978, Titcomb 2003). Because it needs to be

administered several times before adequate cycloplegia is

achieved, homatropine is not considered to be suitable for

cycloplegic refraction in young children and only becomes

an option in patients who are in their late teens or older. It

has been replaced by cyclopentolate in clinical use

(Titcomb 2003).

Tropicamide

Tropicamide is a synthetic derivative of tropic acid. It is a

level 1 POM available in Minim form in 0.5% and 1%

dosages. Tropicamide has a faster onset, 1530 minutes,

and shorter duration of action, 46 hours, compared with

other antimuscarinic agents. This is due to its greater

diffusibility and a higher proportion of unionised drug that

is available for corneal penetration. The 0.5% dosage

produces mydriasis only, with ineffective cycloplegia. With

the 1% dosage maximum cycloplegia is produced 25

minutes after instillation and lasts only about 1520

minutes, after which the cycloplegia is unreliable.

Although it takes up to 6 hours for cycloplegia to wear off

totally, most patients will be able to read 24 hours after

instillation (Bloom 1998, Chang 1978, Titcomb 2003).

Tropicamide has been described as unsuitable for

cycloplegic refraction in children (Leatet al. 1999) and as

clinically useless in all but those patients with very light

irises and in cases of hypersensitivity to cholinergic agents,

eg patients with Downs syndrome (Moore 1997).

Interestingly, however, one study (Twelker et al. 2001)

reported less than 1.00D difference between cycloplegic

retinoscopy results obtained with two drops of

cyclopentolate 1% and two drops of tropicamide 1% on a

group of infants with an average age of 5.7 months. If used

for cycloplegic refraction and if retinoscopy is delayed

beyond 35 minutes after instillation, a further drop isadvised (Bloom 1998).

Other drugs

Two other cycloplegic agents, scopolamine (also known as

hyoscine) and oxyphenonium bromide, are not commonly

used in optometric practice so will not be discussed further

here.

Table 1 summarises the main cycloplegic properties of the

common cycloplegic drugs.

Determination of refractive error

The main reason for using cycloplegic drugs in optometric

practice is to obtain an accurate assessment of refractive

error. Without cycloplegic drugs active accommodation

may affect retinoscopy results. Furthermore, cycloplegic

refraction has been described as an essential part of the

paediatric ophthalmic assessment (Shah et al. 1997) and

the cornerstone of strabismus evaluation (Mehta 1999). As

well as aiding refraction, instilling the cycloplegic drug also

allows a better view of the fundus during ophthalmoscopy;

this is important since retinal lesions may produce visual

loss and strabismus.


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Some eye care professionals advocate cycloplegic

refraction of all children on their first visit to an

optometrist. However, it is probably more appropriate to

select certain groups of patients for whom a cycloplegic

refraction is essential:

those who are poorly cooperative with near or distanceretinoscopy

patients with fluctuating non-cycloplegic retinoscopy

reflex

unexplained reduced VA in children

individuals with manifest strabismus, particularly an

esotropia

those with significant or unstable esophoria

children with a family history of strabismus, amblyopia

or high hyperopia

patients with suspected pseudomyopia

children with a history of strabismus observed by a

parent or guardian

children with anisometropia greater than 1.00DS

cases of reduced accommodation

in high hyperopia in a child of < 2 years

those with suspected latent hyperopia

in variable and inconsistent subjective responses

patients with suspected non-organic visual loss

in symptoms unrelated to the nature or degree of the

manifest refractive error (Evans 2002, Jones & Hodes

1991, Leatet al. 1999, Moore 1997, Viner 2004)

Poor cooperation may have several causes, such as mental

or physical constraints or through an obstreperous

disposition where the child is noisily aggressive and

stubborn (Viner 2004).

Advantages and disadvantages

In general, the advantages of cycloplegic refraction are:

accurate patient fixation is less crucial

accurate retinoscopy can be achieved more easily

latent hyperopia is revealed refractive error can be confirmed (Viner 2004)

there is a better view of the fundus during

ophthalmoscopy

In general, the disadvantages of cycloplegic refraction are:

distress to the patient on instillation of drops

subsequent breakdown in childclinician relationship

photophobia caused by dilated pupils

decreased ability in close-work tasks

a risk of ocular and systemic side effects and adverse

reactions (Tables 2 and 3)

difficulty in assessing axes in the presence ofaberrations resulting from a large pupil diameter (Leat

et al. 1999, Viner 2004)

Furthermore, with atropine, the extended period of

induced blur can act as an effective dissociating device and

may cause patients with an esophoria or intermittent

esotropia accompanied by uncorrected hypermetropia to

lose control of their already fragile binocularity and lapse

into a state of constant esotropia (Mallett 1994, Viner

2004). This will not occur with cyclopentolate (Mallett

1994).

Table 1. Summary of the main antimuscarinic agents and their strengths, duration and indications (Titcomb 2003)

Drug Forms and strengths Time to Duration of action Indications

available maximum effect

Cyclopentolate Multidose eye drops 1560 minutes 24 hours Anterior uveitis

0.5%, 1% Cycloplegic refraction

Single-dose eye drops Fundus photography

0.5%, 1% Ophthalmoscopy

Homatropine Multidose eye drops 3060 minutes 12 days Anterior uveitis

1%, 2%

Single-dose eye drops

2%

Tropicamide Multidose eye drops 25 minutes 6 hours Fundus photography

0.5%, 1% Ophthalmoscopy

Single-dose eye drops

0.5%, 1%


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Table 2. Ocular and systemic adverse reactionsassociated with cyclopentolate (Manny & Jaanus 2001)

Table 3. Systemic adverse reactions associated with

atropine in children (Manny & Jaanus 2001)

Table 4. The residual accommodation, in dioptres, after

instillation of two drops of 1% tropicamide in one eye and

1% cyclopentolate or 5% homatropine in the fellow eye

(Gettes & Belmont 1961)

Wide dilation of the pupil can also create excessivespherical aberration in the ocular media, resulting in

difficult retinoscopy and refraction. The best guideline for

retinoscopy is to neutralise the central 4mm of the pupil,

ignoring the periphery. Also, a retinoscope light of low to

medium intensity helps to reduce any aberrations. In

addition, an allowance for ciliary tonus is sometimes

necessary, and the practitioner must consider this

allowance to determine the appropriate refractive

correction for each patient (Amos 2001, Viner 2004).

Strabismus

When a young patient has an esotropia, cycloplegics can be

used to determine whether the esotropia is fullyaccommodative or not. When a cycloplegic is instilled into

the eyes, the eyes often converge more because

accommodation is incompletely relaxed, and if the patient

tries to overcome this, the cycloplegic convergence

becomes overstimulated. If cycloplegia is complete and the

eyes straighten, this indicates that it is a fully

accommodative esotropia and glasses will hold the eyes

straight. In accommodative esotropia, it is essential to

determine the full amount of hyperopia as it is vital to

prescribe the correct plus-power lenses to relieve the effort

placed on the accommodative convergence system (Amos

2001, Morgan & Arstikaitis 1967). In the presence of a

constant or intermittent strabismus, it is often necessary toocclude one eye. The non-occluded eye maintains fixation

and retinoscopy can be performed on axis with less chance

of error (Moore 1997).

Residual accommodation

Gettes & Belmont (1961) determined residual

accommodation to measure the efficiency of cycloplegic

drugs. They investigated atropine 1%, cyclopentolate 1%,

tropicamide 1% and homatropine 4% with 1% paredrine.

Efficiencies of 100% for atropine, 92% for cyclopentolate,

80% for tropicamide and 54% for homatropine with

paredrine were noted. Table 4 shows the residual

accommodation after drug instillation.

Near-fixation retinoscopy (Mohindratechnique)

There are some potential adverse reactions, side effects

and legal issues on the use of cycloplegic drugs (see below).

Alternatives to using drugs have been suggested. One such

method is near-fixation retinoscopy (often referred to as

the Mohindra technique: Mohindra 1977a, b). This

technique relies on the fact that young children are likely

to be attracted to a retinoscope light in a darkened room.

Ocular Systemic

Irritation Drowsiness

Lacrimation Ataxia

Conjunctival hyperaemia Disorientation

Allergic blepharoconjunctivitis Incoherent speech

Elevated intraocular pressure Restlessness

Visual hallucination

Diffuse cutaneous flush

Depressed salivation / thirst

Fever

Urinary retention

Tachycardia

Somnolence

Excitement / restlessness and hallucinations

Speech disturbances

Ataxia

Convulsions

Age Tropicamide Cyclopentolate Homatropine

(years) at 30 minutes at 60 minutes at 60 minutes

09 6.25 (n = 6) (0) 2.5 (n = 6)

1014 3.65 (n = 20) 1.6 (n = 5) 2.6 (n = 15)


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To keep infants attentive it has been suggested that feedingthem can help; feeding also helps to relax the

accommodation and widens the palpebral aperture

(Mohindra 1975). Retinoscopy is carried out at 50cm on

one eye while the examiner or a carer occludes the other

eye. It is assumed that the eye undergoing retinoscopy is at

its resting accommodation level when the retinoscopy light

is maintained at a minimum. In an adult population the

accommodative response under these conditions has been

shown to remain stable at 0.70D (Owens et al. 1980). The

American Optometric Association recommends near non-

cycloplegic retinoscopy when frequent follow-up is

necessary, when the child is extremely anxious about

instillation of cycloplegic agents and when the child has

had or is at risk of an adverse reaction to cyclopentolate ortropicamide (Scheimanet al. 1997).

Retinoscopy is performed by neutralising the retinal reflex

in the two primary meridians of the eye using loose trial

lenses. The gross sphere cylinder form is then calculated

from the meridional findings. Mohindra (1977b) has

indicated that 1.25D should be added to the spherical

component of the gross sphere cylinder findings. This

adjustment factor was found by comparing subjective

refraction and near retinoscopy results on 27 adults; it

takes into account both the 2.00D working distance and

0.75D residual accommodation (Saunders & Westall 1992).

Results from a study using a larger sample size and infantsubjects indicated greater agreement between near and

cycloplegic retinoscopy (two drops of 1% cyclopentolate)

when 1.00D is subtracted from the spherical component of

the gross retinoscopy result for those patients less than 2

years of age and 0.75D subtracted for those over the age of

2 years (Saunders & Westall 1992). Good reliability

(Mohindra 1975) and validity (Mohindra 1977b) of the

near retinoscopy technique have been reported but some

concerns have also been expressed. Opinions vary as to the

accuracy of this technique; if, during retinoscopy, the light

does not provide a stimulus to accommodation and the eye

assumes its normal resting state of accommodation, it

would seem that the results from this technique would be

reasonably reliable. However, it has been proposed thattonus is dependent on the type of refractive error present,

with hyperopes having a greater amount. If this were true

then it would result in the Mohindra technique

underestimating the amount of hyperopia seen (Viner

2004). Borghi & Rouse (1985) reported that cycloplegic

retinoscopy found on average 0.500.75D more hyperopia

than near non-cycloplegic retinoscopy and Twelker &

Mutti (2001) found an average difference of 1.04D.

However, Wessonet al. (1990) found in their infant group

an average of 2.12D more hyperopia using cycloplegic

retinoscopy with cyclopentolate compared with the near

non-cycloplegic technique and recommended cautionwhen substituting near non-cycloplegic retinoscopy for

cycloplegic refraction.

Interestingly, Chan & Edwards (1994) reported that for

Chinese children (aged 3.55 years), multiplying the

spherical component of the refraction result obtained by

static non-cycloplegic retinoscopy (fixing at 6m) by 1.45,

adding 0.39 to the product while keeping the astigmatic

power unchanged, the total refractive error (ie the error

that would be found using cyclopentolate 1%) can be

accurately estimated.

Adverse Reactions

All cycloplegics have the potential to cause significant

adverse reactions. All the antimuscarinic drugs abolish

normal pupil reflexes to light and near vision and therefore

result in photophobia and a decreased ability to perform

near-work tasks. Photophobia can be reduced by the use of

sunglasses or a brimmed hat. It is also prudent to warn the

parent or carer of a school-aged child that near-work tasks

will prove more difficult until the effects of the drug have

worn off. Also, cycloplegia is contraindicated in all patients

with a history of angle-closure glaucoma (Amos 2001,

Bloom 1998, Viner 2004).

From the clinical perspective, reactions associated with

topically applied cycloplegic agents may be classified as

allergic or toxic. A variety of predisposing factors for

adverse allergic or toxic reactions exist, and these include

use of high concentrations, overdosage and ocular and

systemic conditions allowing increased systemic drug

absorption. Adherence to certain general principles will

reduce the risk of adverse reactions to cycloplegic agents

(Bartlett 1978):

All medications should be kept out of the reach of

children: as few as 20 drops of 1% atropine can be fatal

if taken internally

The ointment form of atropine will decrease the risk ofsystemic absorption

Excessive solution or ointment should be wiped from

the eye after instillation

The lowest concentration and least dosage frequency

consistent with the diagnostic purpose of the drug

should be used; most adverse reactions from

cyclopentolate have followed the administration of a

higher than recommended dose

A conservative approach should be taken in drug

instillation in patients with injected conjunctiva as

hyperaemia increases the rate of systemic absorption


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Before the drug is administered, consideration shouldbe given to its potential adverse effects relative to its

potential diagnostic benefit to the patient

Patients, or their parents, given atropine ointment for

home use should be cautioned to use only as directed;

in contrast to what some patients or parents may

expect, no additional benefit results from receiving

more than the prescribed amount of drug

Any known sensitivity to a specific cycloplegic agent

can often be bypassed by substituting another

cycloplegic

Iris colour

The efficacy of these drugs is influenced by the amount ofiris pigmentation, which is reflected in the colour of the

iris. Until recently the classification of iris colour was

imprecise, and iris pigmentation has been defined in broad

categories such as light or dark, or blue or brown.

Subjective comparisons to standard photographs or to

painted glass eyes have resulted in greater standardisation

and a better understanding of the effect of iris

pigmentation. With new computer technologies, objective

determinations of iris pigmentation promise improved

accuracy in predicting the response and perhaps the

dosage of cycloplegic drugs in individual patients (Manny &

Jaanus 2001).

Cyclopentolate

Adverse reactions from this drug include stinging on

instillation, reduced VA and glare. Adult patients should be

advised not to drive or operate machinery until the effects

of cycloplegia and mydriasis have worn off. The only time

that a miotic drug should be used to reverse the effects of

mydriasis would be if the patient suffered an acute attack

of closed-angle glaucoma following instillation of the

cycloplegic agent. A miotic drug could then be instilled to

reduce intraocular pressure. None of the antimuscarinic

drugs should be used on any patient with a narrow

anterior-chamber angle because of the increased risk of

angle closure (Bloom 1998). In the general population therisk of precipitating such an attack has been reported as 1

in 183 000 (Keller 1975).

Adverse reactions related to the use of cyclopentolate and

tropicamide are less common and less severe than those

associated with other cycloplegic drugs such as atropine

and homatropine, although there have been significant

isolated reports of cases of altered mental state, raised

intraocular pressure and closed-angle glaucoma with

cyclopentolate. Furthermore, heavily pigmented eyes

(dark irises) do not dilate readily (Priestly & Medine 1951)

and therefore extra care should be taken to prevent anoverdose. Cyclopentolate is available in a 2% solution,

although this is not recommended for normal usage since

it may produce psychotic reactions in some individuals.

Central nervous system (CNS) effects are usually reported

after a higher than recommended dose. Compared with

atropine, cyclopentolate causes more CNS effects, such as

confusion, difficulty in speaking, disorientation, aimless

wandering, schizophrenia-like behaviour, restlessness,

apprehension, amnesia and hallucinations (Beswick 1962,

Binkhorst et al. 1963, Kennerdell & Wucher 1972, Mark

1963). Fortunately, none of these lasts for more than a few

hours or leaves permanent problems (Jones & Hodes

1991). Allergic responses to cyclopentolate are rare and

may go unrecognised. Jones & Hodes (1991) described twopaediatric cases of hypersensitivity involving the

development of a facial and upper-body rash that spread to

the arms and legs 46 hours after instillation of two drops

of cyclopentolate 1%. Signs and symptoms had resolved by

the next day. Table 2 summarises the potential ocular and

systemic adverse reactions associated with cyclopentolate.

Atropine

Atropine and homatropine have the potential to cause

more significant systemic side effects than the other

antimuscarinics. Large amounts of atropine absorbed

systemically are toxic or even lethal. The fatal dose ofatropine is about 10mg for children (Mauger & Craig 1996).

Adverse reactions due to the topical use of atropine include

dry mouth, dryness and flushing of the skin, thirst,

restlessness, irritability and disorientation. A more

substantial side effect of atropine may manifest itself as an

allergic contact dermatitis of the lids, producing erythema,

pruritus and oedema. Allergic papillary conjunctivitis and

keratitis have also been reported (Manny & Jaanus 2001).

Atropine can also produce an increase in intraocular

pressure, respiratory depression, tachycardia (an

abnormally rapid heart rate: over 100 beats per minute),

closed-angle glaucoma, altered mental state and

cardiovascular effects. These adverse reactions to atropineare typically described as rendering the patient:

as blind as a bat, because of the cycloplegia

as dry as a bone, through inhibition of sweat and

salivary glands

as red as a beetroot, through increased vasodilation of

the blood vessels of the skin as the body tries to reduce

its temperature by an alternative means

as mad as a hatter, as the CNS effects, including

hallucinations, ataxia (inability to coordinate voluntary

muscle movements, unsteadiness, staggering) and


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psychotic reactions manifest themselves; thesesymptoms indicate an advanced stage of poisoning. In

severe intoxication states, the CNS stimulation and

psychotic phenomena may be followed by depression,

circulatory collapse, coma and death (Bartlett 1978)

Cramp (1976) reported that atropine used therapeutically

might cause a local sensitivity reaction, which is

occasionally violent enough to cause an intensely injected

eye with chemosis along with eczema involving almost all

the face. Atropine should be used with great caution in

patients with Downs syndrome and in patients receiving

systemic anticholinergic drugs because of potential adverse

CNS side effects (Manny & Jaanus 2001). Table 3

summarises potential systemic adverse reactions toatropine in children.

Homatropine

The side effects and adverse reactions from homatropine

are very similar to those of atropine, although they are not

usually as severe. Homatropine is approximately one-tenth

as potent as atropine. Hoefnagel (1961) reported four cases

of ataxia, hallucinations and speech difficulty in children

aged 91/212 years following one drop of 2% homatropine

repeated five to six times at 10-minute intervals. One of

these patients required hospitalisation to manage his

combative behaviour and tachycardia, which persisted for3 days, and hallucinations that persisted for 5 days. Other

reported toxic effects include constant muttering, shouting

and singing, and periods of relative quiet, insomnia,

restlessness, confusion and nausea. Allergic reactions to

homatropine can be seen in the form of lid oedema and

conjunctivitis (Bartlett 1978).

Tropicamide

Tropicamide does not cause many side effects, although it

has the potential to produce an increase in intraocular

pressure, especially for those patients with open-angle

glaucoma (Portney & Purcell 1975) and also an attack of

closed-angle glaucoma, although this is very rare (Keller1975). Wahl (1969) also reported one case in which a 10-

year-old boy developed an anaphylactic shock reaction

following instillation of 0.5% tropicamide drops. It was

reported that immediately after instillation of one drop of

0.5% tropicamide in each eye, the boy fell from his chair to

the floor unconscious. This was followed by generalised

muscular rigidity, opisthotonos, pallor and cyanosis. He

was fully recovered 1 hour later except for residual

drowsiness. This appears to represent an acute

hypersensitivity reaction to 0.5% tropicamide. Adverse

effects to tropicamide like this one are extremely rare

(Bloom 1998, Wahl 1969). Tropicamide has been shown to

be the safest agent (as indexed by changes in bloodpressure and heart rate) for dilated retinal examinations in

neonates (Manny & Jaanus 2001).

Gray (1979) has made several recommendations on

reducing the risk of ocular and systemic side effects

associated with use of cycloplegic drugs:

Avoid overdosage consensus suggests that best

practice is two drops from a Minim separated by 5

minutes, although it is not always possible in clinical

practice to instil two drops into each eye because of the

resistance of the child following the first drop. This will

reduce the amount overflowing on to the cheek and

being systemically absorbed in the nasolacrimal duct Occlude the puncta for 30 seconds following instillation

(Hillet al. 1974)

Choose the least toxic drug available that will give the

desired cycloplegia. For example, cyclopentolate 1% is

less likely to cause side effects than atropine, while

tropicamide is less likely to cause side effects than

cyclopentolate (Wahl 1969), but its cycloplegic

properties are questionable

Be able to recognise adverse systemic reactions

Be aware of predisposing factors for adverse systemic

reactions, such as fair children (Walsh & Hoyt 1969)

and patients with Downs syndrome (Harris & Goodman

1968) Avoid high room temperatures and humidity (Hoefnagel

1961)

Use of Miotics

To reduce the time taken for the effects of a cycloplegic to

wear off naturally, some clinicians advise the use of a

miotic, such as pilocarpine, after the cycloplegic

examination. However, miotic administration can cause

ciliary spasm, brow ache and an increased risk of angle-

closure glaucoma by the pupillary block mechanism.

Furthermore, the effects of 2% pilocarpine have been

assessed in countering cycloplegia. It was found that therewas no significant effect in the decrease of pupil size or the

rate of return of accommodation. In some subjects,

distance VA worsened. Dispensing disposable mydriatic

sunglasses to the patient and allowing the cycloplegic effect

to run its natural course appears to be the best method

(Amos 2001).

Legislation

The following are guidelines that have been drawn up by

the College of Optometrists regarding the general use of


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drugs in UK practice; these can be applied to the use ofcycloplegic drugs (College of Optometrists 2005):

The optometrist has a duty to take due care in the use

of drugs in optometric practice

Practitioners should always act in accordance with the

current medicines legislation controlling the use of

drugs in optometric practice

Practitioners should not consider using a drug or group

of drugs unless they are satisfied that they possess the

knowledge and skills to do so. This is especially

important when a new drug is added to the

Optometrists Formulary

To protect the patient an optometrist has a duty to

maintain a reasonable level of knowledge of drugs andtheir actions through a commitment to appropriate

continuing professional development

Practitioners are encouraged to support adverse drug

reactions reporting schemes

The patients general medical practitioner (GMP) should

be informed of any suspected adverse reaction

When using any diagnostic drug, patients should be

made aware of the effects and possible side effects of the

drug. If the practitioner will not be available to deal with

any emergency that may arise following instillation of

the drug, he should instruct the patient to attend the

local Accident and Emergency department should any

adverse reaction occur

More specific guidelines (College of Optometrists 2005) on

the use of cycloplegia are short and to the point. Section

19.03 states:

Use of a cycloplegic should be considered for the following

reasons:

(a) To have an accurate assessment of the refractive error

(the major factor in amblyopia and/or squint;

(b) To have the best possible view of the fundus within the

limits of cooperation associated with the age of the

child.

Conclusions

Cycloplegic refraction can be of great use in optometric

practice, especially for cases involving latent hyperopia,

esotropia and non-organic visual loss. Non-cycloplegic near

retinoscopy may be appropriate in some cases where

retinoscopy using a distance target has proved ineffective,

but if there is any doubt as to the accuracy of the results a

cycloplegic refraction should be carried out. The most

appropriate cycloplegic agent is cyclopentolate

hydrochloride, preferably in Minim form; the 0.5% dosage

should be used for infants younger than 12 months and

those with CNS anomalies and the 1% dosage on otherpatients. Even though adverse reactions are very rare and

the effects are transient, it is important for the optometrist

to be aware of these and of the types of patients who are

likely to have a negative response to the instillation of

cycloplegic drugs.

References

Amos DM (1978) Cycloplegics for refraction.Am J Optom Physiol Opt55, 23225

Amos JF (2001) Clinical Ocular Pharmacology, 4th edn. Oxford:Butterworth-Heinemann, pp. 4259

Ansons AM, Davis H (2001) Diagnosis and Management of OcularMotility Disorders, 3rd edn. Oxford: Blackwell Science, pp. 27, 28

Bartlett JD (1978) Administration of and adverse reactions tocycloplegic agents.Am J Optom Physiol Opt 55, 22732

Beswick JA (1962) Psychosis from cyclopentolate. Am J Ophthalmol53, 87980

Binkhorst RD, Weinstein GW, Baretz RM, Clahane AC (1963)Psychotic reaction induced by cyclopentolate (Cyclogyl). Results ofpilot study and a double-blind study.Am J Ophthalmol 55, 12435

Bloom J (1998) The College Formulary, pp. 1315. Available online at:www.co l lege-optometr i s t s .o rg /profe ss iona l /op tometr i s t s%27%20formulary.pdf. Accessed October 2004

Boozan CW, Cohen IJ (1953) Ophthaine, a new topical anesthetic forthe eye.Am J Ophthalmol 36, 161921

Borghi RA, Rouse MW (1985) Comparison of refraction obtained bynear retinoscopy and retinoscopy under cycloplegia. Am J Optom

Physiol Opt 62, 16972

Chan OY, Edwards M (1994) Comparison of cycloplegic andnoncycloplegic retinoscopy in Chinese pre-school children. Optom Vis

Sci 71, 31218

Chang FW (1978) The pharmacology of cycloplegics. Am J OptomPhysiol Opt 55, 21922

College of Optometrists (2005) Colleges Guidelines for ProfessionalConduct June 2005. Section 40.05-08. Available online at:www. c o l l e ge - o p t o m e t r i s t s . o r g / p ro f e s s i o n a l / gu i d e l i n e s /

june2005/guidelinesTOC.html. Accessed 29 July 2005

Cramp J (1976) Reported cases of reactions and side effects of thedrugs which optometrists use.Aust J Optom 59, 1325

Doughty M, Field A (2005) Minims proxymetacaine. Available onlineat: www.academy.org.uk/pharmacy/nopain.htm. Accessed 25 July2005

Evans BJW (2002) Pickwells Binocular Vision Anomalies, 4th edn.Oxford: Butterworth-Heinemann, pp. 37, 57

Gettes BC, Belmont O (1961) Tropicamide: comparative cycloplegiceffects.Arch Ophthalmol 66, 33640

Goodman CR, Hunter DG, Repka MX (1999) A randomizedcomparison study of drop versus spray topical cycloplegic application.

Binocul Vis Strabismus Q14, 10710

Gray LG (1979) Avoiding adverse effects of cycloplegics in infants andchildren.J Am Optom Assoc 50, 46570

Harris WS, Goodman RM (1968) Hyper-reactivity to atropine in Downssyndrome.N Engl J Med 279, 40710

Havener WH (1983) Ocular Pharmacology, vol. 5. St Louis: Mosby

Hill JC, Bethell W, Smirmaul HJ (1974) Lacrimal drainage a dynamicevaluation. Part I mechanics of tear transport. Can J Ophthalmol 9,41116


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Hoefnagel D (1961) Toxic effects of atropine and homatropineeyedrops in children.N Engl J Med 264, 16871

Ismail EE, Rouse MW, De Land PN (1994) A comparison of dropinstillation and spray application of 1% cyclopentolate hydrochloride.Optom Vis Sci 71, 23541

Jones LW, Hodes DT (1991) Possible allergic reactions tocyclopentolate hydrochloride: case reports with literature review ofuses and adverse reactions. Ophthalm Physiol Opt 1, 1621

Keller JT (1975) The risk of angle closure glaucoma from the use ofmydriatics.J Am Optom Soc Assoc 46, 1921

Kennerdell JS, Wucher FP (1972) Cyclopentolate associated with twocases of grand mal seizure.Arch Ophthalmol 87, 6345

Leat SJ, Shute RH, Westall CA (1999) Assessing Childrens Vision: AHandbook. Oxford: Butterworth-Heinemann, pp. 1435, 243

Mallett RF (1994) Use of atropine. Optom Today 34, 4

Manny RE, Jaanus SD (2001) Cycloplegics. In: Bartlett JD, Jaanus SD(eds) Clinical Ocular Pharmacology, 4th edn. Oxford: Butterworth-Heinemann, pp. 1501, 154, 158, 161

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Mohindra I (1975) A technique for infant vision examination. Am JOptom Physiol Opt 52, 86770

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1. Which one of the following is not a characteristic of

an ideal cycloplegic drug?

(a) rapid onset of cycloplegia

(b) partial accommodation inhibition

(c) swift accommodation restoration

(d) easy administration

2. Cycloplegic drugs act on the:

(a) parasympathetic nervous system(b) sympathetic nervous system

(c) iris dilator muscle

(d) Mllers muscle

3. Which of the following is useful to know before

instillation of a cycloplegic agent?

(a) K readings

(b) refractive error

(c) colour vision status

(d) cup-to-disc ratio

4. Cyclopentolate 1% stings on instillation because:

(a) it has a pH of 6

(b) it is mixed with anaesthetic

(c) it is diluted with hydrochloric acid

(d) it reacts with melanin granules in the iris

5. The chances of a systemic adverse reaction following

on from instillation of a cycloplegic drug are reduced

if:

(a) an anaesthetic drop is instilled first

(b) the practitioner waits 5 minutes before instilling the

agent into the other eye

(c) eyelid puncta are occluded

(d) the iris is well pigmented

6. In young children the level of cycloplegia is bestjudged by:

(a) the amount of mydriasis

(b) accommodative amplitude

(c) clarity of near text

(d) retinoscopy reflex fluctuation

7. In a patient with lightly pigmented irises, maximum

cycloplegia following instillation of cyclopentolate 1%

would occur after:

(a) 1560 minutes

(b) less than 60 minutes

(c) between 60 and 80 minutes

(d) more than 80 minutes

8. The cycloplegic drug of choice for most primary eye

care practitioners when examining healthy children

over the age of 12 months is:

(a) atropine 1%

(b) cyclopentolate 0.5%

(c) tropicamide 1%

(d) cyclopentolate 1%

9. How much residual accommodation is cyclopentolate1% considered to leave when maximum cycloplegia

has been achieved?

(a) +0.50D

(b) +1.00D

(c) +1.50D

(d) +2.00D

10. According to one study, approximately how much

more hypermetropia did atropine reveal compared to

cyclopentolate?

(a) 0.25D

(b) 0.34D

(c) 0.44D

(d) 0.55D

11. With respect to tropicamide 1%, which one of the

following is true?

(a) Maximum cycloplegia lasts 1520 minutes.

(b) Maximum cycloplegia is produced after 1 hour.

(c) It can be used on all children as a replacement for

cyclopentolate.

(d) It frequently results in systemic adverse reactions.

12. Which one of the following is the most appropriate

correction factor to apply when using the Mohindra

technique on a child less than 2 years old?

(a) +0.25D(b) +0.50D

(c) +0.75D

(d) +1.00D

13. Which one of the following is not a known adverse

reaction to cyclopentolate?

(a) altered mental state

(b) upper-body skin rash

(c) restlessness

(d) brachycardia

Multiple Choice QuestionsThis paper is reference C-2001, CET number EV-6280. Three credits are available. Please use the inserted answer sheet. Copies can beobtained from Optometry in Practice Administration, PO Box 6, Skelmersdale, Lancashire WN8 9FW. There is only one correct answer foreach question.


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14. Which one of the following approximately relates tothe risk of developing acute closed-angle glaucoma

following dilation?

(a) 1 in 85 000

(b) 1 in 185 000

(c) 1 in 285 000

(d) 1 in 500 000

15. With regard to the use of pilocarpine as a miotic

following the instillation of a cycloplegic agent,

which one of the following is true?

(a) Pupil size quickly returns to normal.

(b) There is an increased rate of return of

accommodation.

(c) Distance visual acuity improves following instillation.(d) There is no significant effect on pupil size.


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cycloplegic refraction in optometric practice 1337594763401 2

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