CET Continuing education Ophthalmic drugs Part 2 — The pros and cons of

n active In the second of our series looking at drugs and their use in controls the eye’s process, optometric practice, Catherine Viner discusses cycloplegics, how allowing near focusing they work, when they should be used and how to undertake to occur. The ciliary body is made up mainly cycloplegic refraction. Module C19478, one general CET point for Aof smooth muscle, known as the ciliary optometrists and dispensing opticians muscle. Accommodation occurs when the muscarinic receptors within the are stimulated by the parasympathetic neurotransmitter, acetylcholine (see Part 1 Optician Poor acuity and/or stereopsis 29.06.12). The ciliary muscle then In paediatric patients, these can be contracts, pulling the ciliary body indicative of , potentially forward. Tension in the suspensory caused by uncorrected hypermetropia, ligaments supporting the crystalline , or is reduced. As a result, the lens becomes . To fully investigate the more convex, and thereby increases its cause, a cycloplegic refraction is refractive power. Adequate focus for recommended. nearer targets is then achieved.1 To obtain the true distance correction, Family history of squint, it is imperative that refraction takes amblyopia or hypermetropia place when the patient has relaxed A child is predisposed to these his/her accommodation. For most conditions if a positive family history adults and some children, this can be exists. Should this be the case, due to the achieved by directing the patient to potential risk of amblyopia, it would view a non-accommodative distance seem sensible to fully investigate the target. However, in some individuals, child’s refractive status by performing particularly the young, this is not Figure 1 Cycloplegic agents are particularly useful when a cycloplegic refraction. sufficient and other methods must be examining young children employed to ensure an accurate result. Concentration difficulties Cycloplegia means ‘paralysis of Use of a cycloplegic agent reduces the ciliary body’. In this state, the eye cycloplegic agents, touches on their the need for a patient to concentrate cannot accommodate and the latent therapeutic applications and considers on a distance target to allow static prescription can be determined. alternatives to their use. to take place. This may To obtain cycloplegia, practitioners be beneficial in hyperactive children use drugs known as cycloplegic agents. Indications for cycloplegia or patients with physical or mental These are muscarinic antagonists disabilities. which block the muscarinic receptors Latent hypermetropia within the ciliary muscle (muscarine In young individuals, hypermetropia is Poor accommodation is a chemical that early neurology often masked by the use of highly active Decreased levels of accommodation researchers found to effectively block accommodation. The eye achieves may be found in individuals the acetylcholine receptors at the reasonably clear vision by using its with uncorrected hypermetropia, post ganglionic neurone action site accommodative system to overcome its amblyopia, or oculomotor nerve of the parasympathetic system). If ametropia. When a hypermetropic eye problems. Additionally, there is clear acetylcholine can no longer reach the accommodates, it brings the far point of evidence that in children with Down’s ciliary muscle, accommodation cannot focus closer to the , thus obtaining syndrome2,3 and cerebral palsy4,5 occur. a less blurred image. under-accommodation is considerable. Cycloplegic agents are particularly Unfortunately this can induce If an unexplained reduction in valuable within paediatric increased convergence, which may accommodation levels is discovered, a (Figure 1). They are also beneficial result in an unstable , or fuller investigation of the problem may beyond this age group when examining an , leading to strabismic be made through use of a cycloplegic patients with particular refractive amblyopia. A cycloplegic refraction agent. needs. Furthermore, cycloplegia is is therefore essential in all infants occasionally desirable for patients and children who have a manifest receiving ophthalmological care. This deviation, a high or unstable esophoria Pseudomyopia occurs when a spasm of article explores the diagnostic uses of or a positive history of an eye turn. accommodation causes the muscle tone

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within the ciliary body to be greater than adaptation to the new prescription closure and patients who is necessary for the viewing distance. The by reducing the accommodation and drive should be advised to refrain from ciliary muscle is not relaxed, even for thereby improving acuity. doing so until the effects of the drops distance targets, giving the impression have worn off. of . The accommodative spasm Amblyopia therapy A sensible choice of cycloplegic can be induced by prolonged close Cycloplegia can also be useful as a form agent should be made. Typically, this work and is also associated with stress. of penalisation as part of amblyopia will be hydrochloride, Dispensing a myopic prescription may therapy.9 This method of treatment available in 0.5 per cent and 1.0 per cent encourage more spasm. Pseudomyopia has been found to be as effective as solutions. 0.5 per cent should always be should be considered when the conventional occlusion10 and can be used with infants under the age of six patient’s amplitude of accommodation particularly useful for patients who months. It may also prove useful with is unexpectedly low, and if a are intolerant to patching.11 Use of fair skinned individuals (who have noticeable esophoria exists (due to the ointment (1 per cent) in the less melanin) over 12 years of age. relationship between accommodation good eye reduces its usefulness for For all other patients, the 1.0 per cent and convergence). Releasing the near focusing. The amblyopic eye solution should be used. by use of (with appropriate spectacle correction) Use of 1.0 per cent can a cycloplegic agent allows a more is therefore encouraged to concentrate provide limited cycloplegia if two accurate prescription to be determined. at this distance instead. Care should be drops are instilled, five minutes apart. If this prescription demonstrates a taken to avoid occlusion amblyopia12 However, if retinoscopy does not take reduction in myopia, a diagnosis of and this technique is not recommended place immediately, a further drop pseudomyopia is fairly clear. In some in infants less than 18 months old. should be instilled after 35 minutes. cases an appropriate prescription will This method can provide sufficient be given. However, this may not be In cycloplegia in patients in their late teens tolerated as, in its post cycloplegic state, Cycloplegic agents are prescribed in or above. Manny, Hussein et al15 have the eye reverts to pseudomyopia. If this anterior .13 They allow relaxation also demonstrated that tropicamide 1.0 occurs, instillation of a cycloplegic agent of the inflamed ciliary body and per cent is an effective cycloplegic agent to relax the accommodation while the produce which can reduce in myopic children, while Twelker patient adapts to the new prescription, the formation of posterior synechiae and Mutti16 presented tropicamide can be useful. and relieve pain of spasm. 1.0 per cent as a viable alternative to cyclopentolate in most nonstrabismic Malingering/visual conversion Correct procedure infants. A combination of tropicamide reaction (VCR) 0.5 per cent and 0.5 Malingering has been defined as the Prior to instillation per cent was found to be effective for ‘wilful, deliberate and fraudulent A thorough history and symptoms cycloplegic refractions in nonstrabismic feigning or exaggeration of symptoms of should be taken to ensure that the patient children and those aged older than five illness or injury done for the purpose of a has no known allergy to the cycloplegic years by Fan, Rao et al.17 consciously desired end’.6 VCR describes agent. Caution should be exercised Atropine sulphate 1.0 per cent is an unconscious process whereby a in administering cyclopentolate to usually only chosen if cyclopentolate psychosomatic response results in visual individuals known to have experienced has not produced adequate cycloplegia symptoms, sometimes referred to as CNS disturbances, especially following or prolonged penalisation is required. It ‘hysteria’.7 In either case, a cycloplegic closed head trauma. Some practitioners must not be used on infants under three refraction may reassure the practitioner hold a view that sensitivity to months of age as its prolonged action that the subjective findings are not cycloplegics is increased in patients with renders the infant at risk of stimulus caused by a significant . Down’s syndrome and cerebral palsy.14 deprivation amblyopia. Should a Interestingly, Nandakumar and Leat practitioner be of the opinion that the Refractive surgery reported no adverse reactions to 1 per cent use of atropine would be beneficial in Cycloplegic refractions in adult patients and 0.5 per cent cyclopentolate in their a particular case, he or she may refer have become more widespread in recent examination of children with Down’s the patient to the hospital eye service years due to the increasing popularity syndrome, although they did note that or to an optometrist who has access of refractive surgery. When any sort dilation due to cyclopentolate was to the drugs available on the Level of surgical correction of ametropia is greater in the study population than that 2 exemption list, where atropine is considered, it is vital that the absolute reported in children without Down’s found. refraction is known. If pseudomyopia syndrome.3 is suspected, or if hypermetropia exists, An investigation of unaided visions, On instillation a pre-surgery refraction should include muscle balance and accommodation Care should be taken to minimise the use of cycloplegia. This helps avoid should be made prior to instillation. distress to the patient. Some the undesirable outcome of under/over Intraocular pressures and anterior practitioners administer a local correction.8 chamber angles should also be assessed anaesthetic, usually proxymetacaine where appropriate. 0.5 per cent, immediately before the During adaptation to a new The patient and parent/guardian, if cycloplegic agent. Anaesthetising the hypermetropic prescription applicable, should be made aware of has been shown to reduce If a decision has been made to give the effects of the drug. Careful timing discomfort as the subsequent drops are a new or increased hypermetropic of the procedure should be considered instilled18 and the local anaesthetic can prescription, a child’s overactive to avoid undue inconvenience to the facilitate absorption of the cycloplegic accommodation may blur the vision patient while the cycloplegia and agent. However, if the child objects to through the new glasses. If this occurs, mydriasis subside. Information should the first set of drops, the second set will temporary cycloplegia may assist with be given regarding symptoms of angle- be very hard to administer. opticianonline.net 13.07.12 | Optician | 15 Continuing education CET

Patient discomfort may also be Post cycloplegic check reduced if the cycloplegic agent is Reviewing the patient two or three sprayed onto the gently closed upper days after the cycloplegic refraction has . Ismail, Rouse et al19 and Wong, taken place is useful to ascertain how Fan et al.20 both found this system much of the latent prescription he/she clinically equivalent to using drops in will tolerate. achieving cycloplegia. It is interesting to note that the study by Wong, Fan Arguments against cycloplegia et al involved a population with darkly The use of any drug on any patient pigmented irides. has potential side-effects. Muscarinic It can often be challenging to achieve antagonists are capable of producing adequate cycloplegia in patients with not only local allergic reactions but also darkly pigmented iridies, due to the more widespread adverse reactions. binding effect of the cycloplegic agent Atropine is particularly well known to the melanin in the iris. It is often for its potential to produce an adverse necessary to repeat the instillation of reaction, especially if ingested.13 There cyclopentolate drops in patients with are also reports of CNS effects following dark irides if little effect is seen after the use of cyclopentolate23,24 and an Figure 2 Welch Allyn SureSight hand-held autorefractor the first 10 or 15 minutes. Mohan and account of an anaphylactic reaction to Sharma suggest that the optimal dosage this drug has been given.25 Bagheri, Obviously this technique is only of cyclopentolate 1 per cent in patients Givard et al caution that side-effects suitable for patients who have with brown irides is two drops, instilled are less frequent using one drop of adequate communication skills and in 10 minutes apart.21 cyclopentolate, compared to two or whom visual acuity checks are fairly It should be remembered that three drops.26 straightforward. occlusion of the puncta helps to Another disadvantage to using minimise systemic absorption. cycloplegic agents is the time involved. It Mohindra technique is not ideal to keep patients (particularly This adaptation to near fixation After instillation young ones) waiting for maximum retinoscopy was developed by Mohindra The patient should be monitored cycloplegia to occur. Indeed, it has in the 1970s.28 Mohindra promoted to ensure maximum cycloplegia been demonstrated that a prolonged this technique as an alternative to has occurred before retinoscopy waiting time contributes to the distress cycloplegic retinoscopy, particularly commences. With older children and experienced by children in a paediatric useful in infants. It assumes that, in adults, measurements of the amplitude eye care setting.27 Due to the extended a completely darkened room, the eye of accommodation can be made. With period of cycloplegia which occurs will assume its resting accommodative younger children and infants, dynamic with the use atropine, there is a risk that level and that the retinoscopy light retinoscopy can be used. Once a stable a permanent squint could be established will not stimulate accommodation. point is reached in the reduction of in a child with a large or Owens, Mohindra et al29 showed that accommodation or the increase of the intermittent strabismus. In addition, this is fundamentally the case, with the dynamic lag, it can be assumed that children may decide that they no longer eye assuming an intermediate focus maximum cycloplegia exists. wish to cooperate with the practitioner corresponding to its ‘dark focus’. This is A check to ensure that the drops after eye drops are instilled, and despite shown as a small amount of myopia. reached the cornea can be made by their use, an accurate result cannot be Providing that both tonic assessing pupil size and response obtained. accommodation and the ‘dark focus’ to direct light. Manny, Fern et al22 Clearly, it may be sensible to have points of all patients are identical then confirmed that the time course for other techniques available to control this technique should prove a reliable pupil dilation is not the same as that for accommodation. one in controlling the accommodation. cycloplegia. However, post instillation The author has indeed found can be a useful indicator of Alternative methods for anecdotally that using this technique potential unequal cycloplegia. controlling accommodation on undergraduate students produces In this study the time at which almost identical retinoscopy results maximum cycloplegia was reached Fogging technique to those found when cycloplegia is was also reassessed. Individuals In some individuals, fogging, by adding used. Mohindra and Molinari30 when with dark irides reached maximum positive spheres (typically +0.75DS) examining 5-7 year-old children, and cycloplegia, following use of 1 per cent to the manifest refraction, will relax Borghi and Rouse31 who refracted cyclopentolate, after 30-40 minutes. the accommodation enough to give children between the ages of 3.6 and However, it was discovered that the satisfactory results. After binocular 10 years, found a good correlation same level of residual accommodation balancing, and taking care not to between the retinoscopic results of the was found in those with light irides a stimulate the accommodation, the extra two techniques. mere 10 minutes after instillation. The plus power is reduced in 0.25DS steps. However, Wesson, Mann et al32 author has also found anecdotally that At each step, the practitioner checks suggested that caution should be used maximum cycloplegia in individuals the patient’s visual acuity and should if cycloplegic retinoscopy was to be with light irides can occur before only maintain the reduction of the substituted as the two sets of results, maximum pupil dilation is reached. extra plus power if there is a genuine cycloplegic retinoscopy and near Cycloplegic retinoscopy results are improvement in acuity. The endpoint retinoscopy, for infants and children traditionally recorded in red. If atropine is the maximum plus (or minimum did not match well. Maino, Cibis et has been used, a tonus allowance of minus) power that gives the maximum al33 demonstrated that results from -1.00DS should be made. acuity. children with higher refractive errors

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also showed a poor correlation. One ‘cut’ before prescribing, it is thought that showed the least underestimation theory as to why this might be the results from the Mohindra technique of hyperopia when used without case is that tonic accommodation may would be close to what might actually cycloplegia. This would suggest that vary from individual to individual. It is be prescribed. potential instrument myopia and thought that hypermetropes may have a proximal accommodation could be greater amount of tonic accommodation Autorefractors and managed reasonably satisfactorily in than myopes.34,35 Allen and O’Leary36 photorefractors this type of design. However, Choong found that myopes had a significantly Various studies have been made to and Goh42 concluded that the Grand lower level of tonic accommodation determine whether autorefraction38-42 Seiko WR5100K, which does allow when measured by pinhole technique and photorefraction43-45 without distance target viewing, over minused than non-myopes. Therefore, it might be cycloplegia are adequate in controlling prescriptions in 7-12 year old children concluded that performing the Mohindra children’s accommodation to produce without the use of cycloplegia. technique on higher hypermetropes results comparable to those obtained When considering photorefraction, may give an underestimation of the with cycloplegia. opinion is again divided. Anker, refractive error. Barry and Konig38 concluded that Atkinson et al43 established that Twelker and Mutti16 also pointed use of the Nikon Retinomax monocular a non-cycloplegic videorefractive out that the Mohindra technique takes autorefractor, with a close working procedure, using the Clement Clarke time and practice to perform reliably. distance, could not be recommended isotropic videorefractor VPR-1, They recommended that cycloplegic for non-cycloplegic screening for combined with orthoptic examination, retinoscopy be used by practitioners refractive amblyopia in three-year- was successful in detecting a large who perform a limited number of olds. Wesemann and Dick39 found proportion of infants with significant paediatric examinations. that, with the same instrument, 24 refractive error, indicating that active Suggestions to modify Mohindra’s per cent of children aged 2-12 years accommodation was not a problem correction factor of 1.25DS have been were over-minused when cycloplegia in this method. Blade and Candy45 made by Saunders and Westall.37 They was not induced. However, Buchner, ascertained that the PowerRefractor was believe that using a correction factor Schnorbus et al40 found similar results also capable of detecting large amounts of 1.00DS for children over the age of when comparing those from the Welch of defocus. Conversely, William, two and 0.75DS for those under this Allyn SureSight hand-held autorefractor Lumb et al44 found that the Topcon age give results closer to those found (Figure 2) on non-cyclopleged eyes PR2000 photorefractor underestimated under cycloplegia. to those obtained by cycloplegic hypermetropic refractive errors in An argument exists for not worrying refraction. Shryakumar and Bobier41 children under the age of eight, about any potential slight underestimation intimated that autorefractor designs suggesting that accommodation was not of hypermetropia. Because cycloplegic that incorporated large working well controlled with this instrument. refraction results are often modified or distances and distant fixation targets Conclusion Investigators are divided as to how Multiple-choice questions – take part at opticianonline.net satisfactorily accommodation is controlled with autorefractors and Which of the following correctly describes Which of the following cycloplegic photorefraction, and opinions vary 1a cycloplegic agent? 4agent should be used by an entry level as to the reliability of the Mohindra A Muscarinic agonist optometrist on a brown-eyed eight-year-old technique. There are also definite B Parasympathomimetic child? disadvantages to the use of cycloplegic C Adrenergic antagonist A 0.5 per cent cyclopentolate agents. However, it would seem prudent D B 1.0 per cent cyclopentolate for practitioners to be comfortable with C 0.5 per cent tropicamide the use of cycloplegics and to have Which of the following statements about D 1.0 per cent atropine sulphate some knowledge of the Mohindra 2pseudomyopia is true? technique to enable them to achieve A As it tends to occur in adults, cycloplegia is What is the best way to check that adequate control of accommodation on not necessary 5cycloplegia has been established on a the maximum number of patients. B It occurs where the objective refraction two-year-old child? Further research on levels of tonic suggests emmetropia when the actual axial A Amplitudes of accommodation with an RAF accommodation in young children, length is too long rule particularly hypermetropes, may C The patient reports reduced near vision after B Dynamic retinoscopy identify the need for a correction prolonged reading sessions C Pupil diameter factor to be employed when using D Spasm of accommodation may be related to D ±1.00DS flipper lenses either Mohindra retinoscopy or stress What correction factor is used in the photo/autorefraction. This may foster Which of the following conditions may be Mohindra technique? increased confidence in results obtained 6 ● 3treated with a cycloplegic agent? A None from these techniques. A Cerebral palsy B 0.75DS B Down’s syndrome C 1.25DS References C Anterior uveitis D 1.50DS A full list of references is available from D Hypermetropia [email protected]

Successful participation in this module counts as one credit towards the GOC CET scheme ● Catherine Viner is a senior lecturer administered by Vantage and one towards the Association of Optometrists Ireland’s scheme. at the University of Bradford School of The deadline for responses is August 9 2012 Optometry and Vision Sciences and has a special interest in paediatrics

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