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Occlusion treatment studies of amblyopia treatment are ambiguous.
- Philip Lempert (15 October 2007)
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Modern amblyopia management
- Annegret H Dahlmann-Noor, Anthony J. Vivian (30 October 2007)
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Occlusion therapy – non-compliance issues
- Sandra D Gawley, Chester, Cheshire, CH2 1UL (21 November 2007)
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Philip Lempert, Ophthalmologist Ithaca, NY, USA 14850
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The recent editorial 1 and report2 concerned with occlusion treatment for amblyopia include some ambiguities. Loudon and Simonz correctly note that “poor initial visual acuity is the most important clinical predictor for poor treatment outcome.”1 They did not consider anatomic defects as the etiology for severe visual impairments and attribute the poor outcomes to solely to compliance failure. Amblyopia is essentially a diagnosis of exclusion that is applied after organic causes for impaired vision have been eliminated. Optic nerve hypoplasia, for example, is recognized to be “an important cause of childhood visual disability”3 and perhaps the most common optic disc anomaly encountered in clinical practice.4 Accurate diagnosis of this condition requires imaging and measurements which were apparently not utilized in this study. 2 Snowdon and Stewart-Brown’s study of the amblyopia related literature found "no studies of natural history of amblyopia, no studies sufficient to draw any firm conclusions about the impact of amblyopia on quality of life, no randomised controlled trials of treatment vs. no treatment and only one prospective controlled trial of screening"5 The report by Stewart et al2 also fails to include untreated or placebo subjects. The mean age of the subjects in this study was 5.6 years. This is a period when children are learning to read. Improved responses to an eye chart would be expected due to education regardless of treatment protocols. Their findings that “the final level of attainment for all ages between 3 and 8 years is the same” and the similarity of responses to different amounts of occlusion reinforce the likelihood that patching has little to do with final results.2 The lack of an untreated cohort makes the attribution of improvement solely to occlusion treatment doubtful. The gold standard for clinical trials includes placebo groups. 6 Until amblyopia treatment studies include untreated subjects for comparison and incorporate objective diagnostic methods they will continue to produce uncertain results. 1 Loudon SE, Simonz HJ. Editorials: Occlusion therapy for amblyopia BMJ - 2007;335:678-679 2 Stewart CE, Stephens DA, Fielder AR, Moseley MJ. Objectively monitored patching regimens for treatment of amblyopia: randomised trial BMJ 2007;335;707- 714 3 Oster SF, Sretavan DW. Connecting the eye to the brain: the molecular basis of ganglion cell axon guidance. Brit J Ophthalmol 2003;87:639-645 4 Brodsky MC, Baker RS, Hamed LM. Pediatric Neuro-ophthalmology. Springer-Verlag, New York, Inc. 1996. Page 43 5 Snowdon S, Stewart-Brown SL. Preschool vision screening: results of a systematic review. York: NHS centre for reviews, 1997 Report 9). 6 Meinert CL. Guest Editorial. Clinical Trials: The Gold Standard for evaluation of therapy. Ophthalmology 103(6), June 1996 869-870 Competing interests: None |
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Annegret H Dahlmann-Noor, Research Fellow Institute of Ophthalmology London EC1V 9EL, Anthony J. Vivian
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Dr Lempert’s letter 1 commenting on Stewart et al’s article on amblyopia management 2 contains a number of statements which do not take into account recent insights into the biology of amblyopia nor the evidence on which modern amblyopia management is based (recently reviewed in 3 4 5). Firstly, amblyopia is no longer a diagnosis of exclusion. Amblyopia is a developmental anomaly of spatial vision usually associated with strabismus, anisometropia or form deprivation early in life. 6 Modern neuro-imaging studies have demonstrated the structural correlates of amblyopia and the complexity of visual processing anomalies in this condition. 7 Secondly, a series of randomised clinical trials has demonstrated that three treatment modalities are very effective in treating amblyopia: correction of refractive errors, occlusion of the fellow eye for two or six hours a day, and pharmacological blurring of the fellow eye by topical atropine eyedrops. Correction of refractive errors alone improves visual acuity (VA) and can even lead to resolution of amblyopia. 8 9 10 Vision improvement is greatest during the first few weeks of treatment, but can continue for up to thirty weeks after glasses are first prescribed. 8 9 10 Hence, in the presence of some early improvement in VA with glasses, many paediatric ophthalmologists now wait for at least sixteen weeks or until VA demonstrably fails to improve further before deciding whether additional treatment is required. 11 Residual amblyopia is usually treated by occlusion of the fellow eye. 12 13 To reduce the emotional burden on children and parents when the better seeing eye is occluded, some use topical atropine with similar results. 14 However, atropine carries the risk of disrupting existing binocular function. 15 Dr Lempert criticises the lack of a control arm in Stewart et al’s study. He has repeatedly voiced the same criticism about previous amblyopia studies. 16 17 18 19 However, by now three randomised trials which included control subjects have been published. 20 21 11 Children with unilaterally reduced vision improve less when untreated than when receiving optical correction with or without fellow eye occlusion. 20 Evaluation of occlusion therapy including a control group with optical correction alone has demonstrated a clear benefit of occlusion treatment. 21 11 Thirdly, Dr Lempert calls for exclusion of anatomic optic nerve defects in cases of treatment failure. We agree with this criticism, but assume that Stewart et al. would have performed relevant tests as by routine clinical practice, without including details in their report. Tests demonstrating structural defects of optic nerve or higher visual pathways require a sophisticated setup and skilled examiners and are stressful for children. In clinical amblyopia management dilated fundoscopy is routinely performed during the initial workup, whilst imaging and electrodiagnostic studies remain reserved for those children who fail to respond to treatment. Following the prescription of glasses or occlusion children are examined at regular intervals. Failure of the VA to improve then justifies more elaborate tests which would otherwise be unnecessarily inflicted on much greater numbers of young children. Lastly, Dr Lempert considers education and learning to read to be a confounding factor in treatment evaluation. This argument is not tenable, as pointed out in replies to his previous comments on other studies. 19 Improvement in VA as a result of amblyopia treatment is greatest within the first five or six weeks of occlusion therapy, 11 13 22 a timescale far shorter than that required to acquire reading skills. The present randomised trial by Stewart et al. 2 fills a gap in the evidence base. 23 24 Previous studies demonstrated that prescription of shorter time periods of occlusion delivered comparable results to longer durations, but did not monitor compliance with occlusion. 12 13 Parents tend to over-estimate the wearing time of eye patches, and patches may be worn for only around 50% of the prescribed time. 25 Using electronic occlusion monitors, Stewart et al. have now filled the gap between prescription and compliance. This latest piece of evidence will no doubt enhance the modern management of amblyopia. 1. Lempert P. Occlusion studies are ambiguous. BMJ 2007;335:842. 2. Stewart CE, Stephens DA, Fielder AR, Moseley MJ. Objectively monitored patching regimens for treatment of amblyopia: randomised trial. BMJ 2007;335(7622):707. 3. Kiorpes L. Visual processing in amblyopia: animal studies. Strabismus 2006;14(1):3-10. 4. Levi DM. Visual processing in amblyopia: human studies. Strabismus 2006;14(1):11-9. 5. Holmes JM, Repka MX, Kraker RT, Clarke MP. The treatment of amblyopia. Strabismus 2006;14(1):37-42. 6. Ciuffreda KJ, Levi DM, Selenow A. Amblyopia: Basic and Clinical Aspects Boston: Butterworth-Heinemann, 1991. 7. Anderson SJ, Swettenham JB. Neuroimaging in human amblyopia. Strabismus 2006;14(1):21-35. 8. Stewart CE, Moseley MJ, Fielder AR, Stephens DA. Refractive adaptation in amblyopia: quantification of effect and implications for practice. Br J Ophthalmol 2004;88(12):1552-6. 9. Cotter SA, Edwards AR, Wallace DK, Beck RW, Arnold RW, Astle WF, et al. Treatment of anisometropic amblyopia in children with refractive correction. Ophthalmology 2006;113(6):895-903. 10. Cotter SA, Edwards AR, Arnold RW, Astle WF, Barnhardt CN, Beck RW, et al. Treatment of strabismic amblyopia with refractive correction. Am J Ophthalmol 2007;143(6):1060-3. 11. Wallace DK, Edwards AR, Cotter SA, Beck RW, Arnold RW, Astle WF, et al. A randomized trial to evaluate 2 hours of daily patching for strabismic and anisometropic amblyopia in children. Ophthalmology 2006;113(6):904-12. 12. Holmes JM, Kraker RT, Beck RW, Birch EE, Cotter SA, Everett DF, et al. A randomized trial of prescribed patching regimens for treatment of severe amblyopia in children. Ophthalmology 2003;110(11):2075-87. 13. Repka MX, Beck RW, Holmes JM, Birch EE, Chandler DL, Cotter SA, et al. A randomized trial of patching regimens for treatment of moderate amblyopia in children. Arch Ophthalmol 2003;121(5):603-11. 14. A randomized trial of atropine vs. patching for treatment of moderate amblyopia in children. Arch Ophthalmol 2002;120(3):268-78. 15. Kushner BJ. Concern about the Pediatric Eye Disease Investigator Group 2-year follow-up study. Arch Ophthalmol 2005;123(11):1615-6. 16. Lempert P, Leiba H. Occlusion therapy in amblyopia. Ophthalmology 2002;109(10):1757-8; author reply 1758. 17. Lempert P. The effectiveness of patching for amblyopia should be tested with untreated control subjects. Arch Ophthalmol 2004;122(3):423-4; author reply 424-5. 18. Lempert P. Contradictions in the amblyopia treatment studies. Arch Ophthalmol 2006;124(2):285; author reply 285-7. 19. Lempert P. The pediatric eye disease investigator group report may be too optimistic about efficacy of treatment. Pediatrics 2004;114(5):1366; author reply 1366-7. 20. Clarke MP, Wright CM, Hrisos S, Anderson JD, Henderson J, Richardson SR. Randomised controlled trial of treatment of unilateral visual impairment detected at preschool vision screening. BMJ 2003;327(7426):1251. 21. Scheiman MM, Hertle RW, Beck RW, Edwards AR, Birch E, Cotter SA, et al. Randomized trial of treatment of amblyopia in children aged 7 to 17 years. Arch Ophthalmol 2005;123(4):437-47. 22. Stewart CE, Moseley MJ, Stephens DA, Fielder AR. Treatment dose- response in amblyopia therapy: the Monitored Occlusion Treatment of Amblyopia Study (MOTAS). Invest Ophthalmol Vis Sci 2004;45(9):3048-54. 23. Gottlob I, Awan M, Proudlock F. The role of compliance in 2 vs 6 hours of patching in children with amblyopia. Arch Ophthalmol 2004;122(3):422-3; author reply 424-5. 24. Bloom JN. The effect of patient compliance on the assessment of amblyopia treatment. Arch Ophthalmol 2004;122(3):422; author reply 424-5. 25. Awan M, Proudlock FA, Gottlob I. A randomized controlled trial of unilateral strabismic and mixed amblyopia using occlusion dose monitors to record compliance. Invest Ophthalmol Vis Sci 2005;46(4):1435-9. adahlmann@doctors.net.uk Competing interests: None declared |
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Sandra D Gawley, ST3 ophthalmology Countess of Chester Hospital, Chester, Cheshire, CH2 1UL
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I read with great interest the article recently published by Stewart et al on objective monitoring of patching regimens for treatment of amblyopia.1 The results of their study highlight the major issue of non- compliance with occlusion times. In the clinic setting it is important to set achievable occlusion times – it is unrealistic to expect busy parents to be able to supervise lengthy patching regimes of 6-12 hours per day. Stewart et al’s finding that children in their study received on average 66% and 50% of their prescribed occlusion of six and twelve hours a day, respectively, underline this. Their study further confirms that compliance is generally poorer with longer regimes a finding previously noted by the ‘The Pediatric Eye Disease Investigator Group’ (PEDIG).2 Importantly Stewart et al observed ‘a plateau of improvement in outcome at about four hours a day’, although they note that younger children may require less patching. These findings may help guide and tailor treatment decisions in everyday practice and hopefully encourage more realistic patching regimes amongst practitioners and help parents feel a sense of achievement in being able to comply with prescribed treatment. Stewart et al’s results are all the more convincing as they monitored with electronic occlusion dose-monitor devices compared to a parental calendar system used in other research settings.3 Translating such study findings into practice however is another major hurdle – Wygnanski-Jaffe et al 4 investigated the effect of the PEDIG study, published in May 2003,3, which showed similar improvements in visual acuity in both the two and six hour patching groups in moderate amblyopes aged 3 to 7 years. They surveyed J AAPOS members and found that only 55% had decreased their prescribing regimes at least sometimes in 2006 though this figure had increased compared to a previous survey in 2003. As well as realistic daily patching regimes compliance might also be improved by full explanation and involvement of parents in treatment plans - one study has suggested setting a weekly target for parents and allowing them to decide the daily dosage thus increasing flexibility for the family.5 This may be particularly helpful in the maintenance phase of occlusion therapy which may be necessary for a lengthy period of time.6 Also occlusion may be effective when combined with close work 3,7 and parents should be advised and encouraged to take full advantage of this. Exciting developments in alternative amblyopia treatment are at a preliminary stage – the Interactive Binocular Treatment (I-BiT) system incorporates virtual-reality technology and software providing 2D and 3D games and videos via a stereo display allowing binocular treatment of amblyopia.8 Waddingham et al report on six children treated with this system, mean age 6.25 years (5.42-7.75 years) and five of the six children had visual improvement (average increase of 10 letters).9 Cleary et al have recently published their results with this system in the older amblyope (6.1-11.4 years) who had either not complied with or responded to occlusion. They found sustained improvements in visual acuity in 58%.10 Hopefully this will be truly revolutionary avoiding the side effects and burden of occlusion treatment. References 1.Stewart CE, Stephens DA, Fielder AR, Moseley MJ, ROTAS Cooperative. Objectively monitored patching regimens for treatment of amblyopia: randomised trial. BMJ 2007;335(7622):707 2.The Pediatric Eye Disease Investigator Group. A randomized trial of patching regimens for treatment of severe amblyopia in children. Ophthalmology 2003;110(11):2075-87 3.The Pediatric Eye Disease Investigator Group. A randomized trial of patching regimens for treatment of moderate amblyopia in children. Arch Ophthalmol 2003;121(5):603-11 4.Wygnanski-Jaffe T, Levin AV. The effect of the randomized trial of patching regimens for treatment of moderate amblyopia on pediatric ophthalmologists: 3-year outcome. J AAPOS 2007;11(5):469-72 5.Tripathi A, O’Donnell NP, Holden R, Kaye L, Kaye SB. Occlusion therapy for the treatment of amblyopia: letting the parents decide. Ophthalmologica 2002;216(6):426-29 6.Ainsworth JR. Topics in amblyopia. Eye News 1996;3:7-8 7.Pediatric Eye Disease Investigator Group. A randomized trial to evaluate 2 hours of daily patching for strabismic and anisometropic amblyopia in children. Ophthalmology 2006;113(6):904-12 8.Eastgate RM, Griffiths GD, Waddingham PE et al. Modified virtual reality technology for treatment of amblyopia. Eye 2006;20(3):370-74 9.Waddingham PE, Butler TKH, Cobb SV et al. Preliminary results from the use of the novel Interactive Binocular Treatment (I-BiTTM) system, in the treatment of strabismic and anisometropic amblyopia. Eye 2006;20(3):375- 78 10.Cleary M, Moody AD, Buchanan A, Stewart H, Dutton GN. Assessment of a computer-based treatment for older amblyopes: the Glasgow Pilot Study. Eye 2007 Oct 12; (Epub ahead of print) Competing interests: None declared |
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