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Tackling the greatest challenge in surgery

D F Chang

Br. J. Ophthalmol. 2005;89;1073-1077 doi:10.1136/bjo.2005.068213

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Cataract where they will all undergo their sur- ...... gery on a single day. After several days of in-house follow up, they are trans- ported back to their rural villages where Tackling the greatest challenge in a local postoperative visit and refraction are performed 1 month later by the cataract surgery Aravind staff. This standardised Aravind system streamlines and centra- D F Chang lises cataract care by performing all surgery in the main hospital.10 ...... Founded in 1994 by Dr Sanduk Ruit, the Tilganga Centre is a shining From the standpoint of cost effectiveness manual small incision example of an efficient eye care delivery cataract surgery is clearly superior to the alternatives system on a smaller scale. Dr Ruit has developed his own variation of the 11–13 espite all that modern technology 200 000 procedures performed annually manual, sutureless SICS. Tilganga has done to advance the treatment in the Aravind system, 70% are provided Eye Centre is also financially self sus- Dof , our greatest challenge free. taining wherein private care subsidises continues to be the large and increasing While private cataract patients at charity care. They also have their own backlog of cataract blindness in devel- Aravind may pay anywhere from $200– IOL manufacturing facility, which, like oping countries.1–5 While in North $300 to undergo phacoemulsification that at Aravind, is able to supply low America and western Europe, intraocu- with foldable IOLs imported from the cost IOLs to other developing countries. lar (IOL) research and development United States, the non-paying cataract Because the rural population in Nepal is are primarily directed towards reversing patients are treated for less than $15 per so widely scattered among mountain lens ageing (), millions in case, including the IOL. This is accom- villages that are accessible only by foot, developing nations with reversible plished by performing a manual, suture- the Tilganga system strives to deliver blindness caused by cataracts go less, small incision extracapsular portable cataract care by transporting untreated. procedure with re-usable equipment the necessary staff and equipment to 14 15 Modern phacoemulsification and supplies.6–9 Their IOL manufactur- remote eye camps. Using a single machines are expensive to purchase ing facility, Aurolab, produces poly(- portable operating table, the Tilganga and maintain, have relatively high dis- methlymethacrylate) (PMMA) IOLs for surgeons can also perform more than 10 posable costs, and require extensive less than $5 per lens. Following a cataract surgeries per hour. As at surgical training. Furthermore, for the retrobulbar block, the nucleus is Aravind, the high volume, cost effective more advanced and mature cataracts expressed through a capsulorhexis and Tilganga surgical techniques and proto- typical of underserved populations, per- a temporal, self sealing 6.0–6.5 mm cols are standardised across their surgi- forming phacoemulsification becomes scleral pocket incision. Manual cortical cal teams. more difficult and complication prone. cleanup precedes capsular bag implan- Though of a different scale and What is needed is a high volume, cost tation of a PMMA IOL. The technique is serving different types of communities, effective, low technology procedure that commonly abbreviated as manual SICS Aravind and Tilganga are complemen- can treat the most advanced of cataracts (small incision cataract surgery). tary models of how best to address the with a low complication rate in the world’s backlog of cataract blindness. shortest amount of time. They demonstrate that the solution An efficient, high volume system This very goal is being achieved in a requires not just a cost effective surgical utilising low cost, sub-5 minute pro- handful of international programmes technique, but also an entire system of cedures to tackle advanced catar- that are providing a hopeful paradigm efficient and financially self sustaining for overcoming worldwide cataract acts with minimal complications is cataract care delivery. There must be a blindness. I have had the privilege of clearly the best way to use the system for attracting, screening, diag- visiting both the Aravind Eye Hospital scarcest and most precious asset of nosing, and transporting cataract network in southern India, and the the system—the cataract surgeon patients to and from rural camps. Tilganga Eye Centre in Kathmandu, There must be a source of low cost Nepal. Seeing first hand how their While the procedure itself seems IOLs, medications, and supplies. Most systems provide high volume, low cost straightforward, it is the stunning importantly, there must be highly coor- cataract surgery is an awe inspiring speed, skill, and efficiency with which dinated teams of dedicated ophthalmol- experience for any visiting ophthalmol- it is performed that must literally be ogists and support staff, who execute ogist. seen to be believed. By alternating their roles with military precision. To Founded in 1976 by the now 87 year between two parallel operating room assure maximum efficiency and repro- old Dr G Venkataswamy, Aravind Eye tables, a single surgeon is able to ducibility, there must be a standard Hospital has grown into a network of perform over 15 cases per hour by protocol for every aspect of care. five regional eye hospitals providing consistently completing sub-5 minute In this issue of BJO (p 1079), high level ophthalmic care to the poor procedures on the densest of cataracts Venkatesh and co-authors provide a population of southern India. Private with no intervening turnover time. To detailed outcome study of the high paying patients comprise approximately ensure efficiency across different surgi- volume, manual SICS (small incision 30% of their patient base. This revenue cal teams, every aspect of the procedure cataract surgery) method used at funds 70% of their services that are is standardised, from preoperative Aravind. Two days’ surgical volume for provided at no cost to the indigent via a patient and instrument preparation to three cataract surgeons (,600 cases) financially self sustaining programme the surgical steps themselves. Having were randomly selected and reviewed that receives minimal government reim- been screened in outlying eye camps, as retrospectively. Despite a high percen- bursement. In terms of cataract surgery, many as 300–400 cataract patients will tage of advanced and mature cataracts, this means that of the approximately by bussed to an Aravind eye hospital operative complications were extremely

www.bjophthalmol.com Downloaded from bjo.bmjjournals.com on 8 September 2005 1074 EDITORIAL low, and vitreous loss occurred in less Tilganga, are the most promising, effi- 7 Prajna NV, Chandrakanth Ks, Kim R, et al. The Madurai intraocular lens study II: clinical than 1% of cases. Understandably, cacious, and cost effective means to outcomes. Am J Ophthalmol 1998;125:14–25. stringent postoperative outcome data eradicate cataract blindness in develop- 8 Natchiar G, DabralKar T. Manual small incision with long term follow up are not easily ing countries. Beyond the impressive suture less cataract surgery-An alternative technique to instrumental phacoemulsification. attainable in a rural cataract camp productivity of these two institutions, Operative Techniques Cataract Refract Surg population. However, with 6 week fol- equally important has been their desire 2000;3:161–70. low up of nearly 90% of the patients, and ability to train surgical teams from 9 Balent LC, Narendran K, Patel S, et al. High other developing countries in their volume sutureless intraocular lens surgery in a 95% achieved a best corrected visual rural eye camp in India. Ophthalmic Surg Lasers acuity of at least 6/18 (not excluding methods of cataract surgery. An effi- 2001;32:446–55. macular or other pathology). These out- cient, high volume system utilising low 10 Natchiar G, Robin AL, Thulasiraj R, et al. cost, sub-5 minute procedures to tackle Attacking the backlog of India’s curable blind; the comes are all the more impressive Aravind Eye Hospital model. Arch Ophthalmol considering that almost 90% of the advanced cataracts with minimal com- 1994;112:987–93. patients had preoperative vision of 5/60 plications is clearly the best way to use 11 Ruit S, Tabin GC, Nissman SA, et al. Low-cost the scarcest and most precious asset of high-volume extracapsular cataract extraction or worse, and that the surgical time for with posterior chamber intraocular lens these nearly 600 patients averaged the system—the cataract surgeon. implantation in Nepal. Ophthalmology 3.75 minutes. Br J Ophthalmol 2005;89:1073–1074. 1999;106:1887–92. 12 Ruit S, Paudyal G, Gurung R, et al. An innovation How does the manual, sutureless doi: 10.1136/bjo.2005.068213 in developing world cataract surgery: sutureless SICS compare to other cataract meth- extracapsular cataract extraction with intraocular ods? One prospective randomised study Correspondence to: D F Chang, University of lens implantation. Clin Experiment Ophthalmol California, San Francisco, Los Altos, CA 2000;28:274–9. determined that this technique resulted 94024, USA; [email protected] 13 Hennig A, Kumar J, Yorston D, et al. Sutureless in better uncorrected acuity than stan- cataract surgery with nucleus extraction: outcome dard extracapsular cataract extraction.16 of a prospective study in Nepal. Br J Ophthalmol control is particularly 2003;87:266–70. REFERENCES 14 Pokharel GP, Regmi G, Shrestha SK, et al. important in populations that have Prevalence of blindness and cataract surgery in limited access to spectacles. I recently 1 World Health Organization. Global initiative for Nepal. Br J Ophthalmol 1998;82:600–5. participated in a prospective randomised the elimination of avoidable blindness, WHO Fact 15 Pokharel GP, Selvaraj S, Ellwein LB. Visual Sheet No 213. Geneva: WHO, Feb, 2000. functioning and quality of life outcomes among trial at the Tilganga Eye Centre compar- 2 Dandona R, Dandona L. Socioeconomic status cataract operated and unoperated blind ing manual, sutureless SICS with phaco and blindness. Br J Ophthalmol populations in Nepal. Br J Ophthalmol in a cataract camp population. While the 2001;85:1484–8. 1998;82:606–10. 3 Arnold J. Global cataract blindness: the unmet 16 Gogate PM, Deshpande M, Wormald RP, et al. data analysis is not complete, I can challenge [editorial]. Br J Ophthalmol Extracapsular cataract surgery compared with attest to the difficulty of performing 1998;82:593–4. manual small incision cataract surgery in phaco in a camp setting with a high 4 Thylefors B. A global initiative for the elimination community eye care setting in western India: a of avoidable blindness [editorial]. randomised controlled trial. Br J Ophthalmol incidence of advanced cataracts and Am J Ophthalmol 1998;125:90–3. 2003;87:667–72. poor corneal visibility. Finally, from the 5 Minassian DC, Mehra V. 3. 8 million blinded by 17 Gogate PM, Deshpande M, Wormald RP. Is standpoint of cost effectiveness, manual cataract each year: Projections from the first manual small incision cataract surgery affordable epidemiological study of incidence of cataract in developing countires? A cost comparison with SICS is clearly superior to the alterna- blindness in India, Br J Ophthalmol extracapsular cataract extraction. Br J Ophthalmol tives.17 18 1990;74:341–3. 2003;87:843–6. Outcome studies such as these pro- 6 Civerchia L, Ravindran RD, Apoorvananda SW, 18 Muralikrishnan R, Venkatesh R, Prajna NV, et al. et al. High volume intraocular lens surgery in a Economic cost of cataract surgery procedures in vide convincing evidence that surgical rural eye camp in India. Ophthalmic Surg Lasers an established eye care centre in Southern India. systems, such as those at Aravind and 1996;27:200–8. Ophthalmic Epidemiol 2004;11:369–80.

Periorbital haemangiomas haemangioma more commonly.12 Why ...... do haemangioma have a predilection for areas around the , or do they? The astigmatism seen with periocular hae- Periorbital haemangiomas mangioma is usually attributed to pres- sure effect of the tumour, but is there W V Good evidence to support this conclusion, or to validate that this is always the cause ...... of astigmatism? Why does astigmatism Paediatric ophthalmology’s stepchild? often persist after the tumour regresses? Which locations for tumours are most likely to cause or contribute to amblyo- very paediatric ophthalmology management is based on anecdote and pia? Again, the answer to these ques- practice cares for infants and young clinical judgment and, in many cases, is tions is not fully known. Echildren with periorbital haeman- optional or elective. Such is the state of the practice of gioma, and yet there is very little The aetiology of periocular haeman- medicine as it pertains to these evidence based research to guide treat- gioma is also debated. Current opinion tumours: many questions with far too ment. Options for management gener- holds that haemangiomas occur more few answers. And so it is ironic and ally include topical, intralesional or frequently in premature infants, yet fitting that Ranschod and colleagues in systemic steroids, surgical resection, or older research on this subject sug- their paper reported in this issue of the no treatment at all, as haemangioma gests that this finding is caused by BJO (p 1134) shed no light on manage- usually involute after a period of ascertainment bias—that is, premature ment of periorbital haemangioma, growth. When tumours block the infants are observed more often than despite a thorough review of the litera- visual axis, aggressive intervention is full term infants, leading observers to ture and a thoughtful meta-analysis of mandatory. In almost every other case, conclude that premature infants develop research on the subject. Rather than

www.bjophthalmol.com Downloaded from bjo.bmjjournals.com on 8 September 2005 EDITORIAL 1075 criticise the authors for taking readers of location around the eyes highly variable photographic reading centre where the BJO down a blind alley, we should in terms of extent, location, and size. masked investigators would interpret be grateful to them for identifying a very These facts make it very difficult to external findings. important and generally disregarded compare treatments at all. How can The recent explosion of developmen- problem, the periorbital haemangioma. treatment of a globular haemangioma tal and molecular biology research offers While this tumour continues to occur at of the upper outer lid be compared to an intriguing and different venue for a significant frequency, and to threaten the same treatment for the same type research on this subject, too. The hae- vision and appearance, its epidemiology, and size tumour of the upper inner lid? mangioma’s biological behaviour dic- cause, biology, and management are in Never mind that the haemangioma tates its effects on vision. This is need of further study. could be diffuse, affect both lids, start obvious in the case of occlusion. The Should the reader then conclude that at an earlier age in some infants, occur large and rapid growing tumour is more the periocular haemangioma is, indeed, in a premature infant, or occur in likely to cause occlusion, , a sort of stepchild in paediatric ophthal- conjunction with tumours in other and astigmatism, whether or not one mology research, largely ignored and locations. All of these factors could ascribes to the pressure theory of hae- second fiddle to other conditions such influence the effect of the haemangioma mangioma induced astigmatism. as amblyopia and ? If the on , amblyopia, tumour Tumour biology could influence astig- answer to this is affirmative, then it may growth, and so on. Scientists have matism and cosmesis in more subtle be useful to explore the means to beat understandably avoided controlled stu- ways, as well. Knowledge that a given this condition. One reason might be that dies on this problem, because experi- haemangioma has biological character- the pathology and effects of these mental design is difficult. istics linked to rapid growth, or astig- tumours generally fall outside the pur- Consequently, case reports have pro- matism, or significant cosmetic changes, view of many of us. The periorbital vided the foundation for knowledge would help guide clinical intervention. haemangioma, after all, is a tumour, about periocular haemangioma and An amalgamation of clinical and basic often responsible for cosmetic changes. their management. Case reports and science research for the study of man- Ophthalmologists generally do not have series are often maligned as second class agement of periorbital haemangioma experience with laser treatments for science, anecdotal, uncontrolled, and could lead to earlier detection of proble- haemangioma, and may be happy failing to test a hypothesis. But without matic tumours. enough to defer systemic treatment case reports noting that astigmatism Let’s hope that Ranshod and collea- implementation to paediatricians and sometimes improves with intralesional gues, and others, carry forth their dermatologists. Consider, too, that very injections, or of side effects of treat- concerns about this neglected problem serious side effects from ophthalmolo- ment, including adrenal suppression and work to rectify the current situa- gist led treatment have been reported, and blindness, clinicians would have tion, where a shortage of evidence is including blindness associated with very little data at all to guide manage- used to support clinical decision mak- intralesional injection. ment of haemangioma. Case reports ing. The periorbital haemangioma will continue to be important to deserves full citizenship in the world of describe effects of treatment for this paediatric ophthalmology research. While this tumour continues to occur condition. at a significant frequency, and to Br J Ophthalmol 2005;89:1074–1075. Lastly, we should try to imagine the doi: 10.1136/bjo.2005.073411 threaten vision and appearance, its design of a controlled clinical trial to test epidemiology, cause, biology, and treatment for periorbital haemangioma. Correspondence to: W V Good, Smith management are in need of further Kettlewell Eye Research Institute, 2318 Fillmore This is the charge set forth by Ranshod, Street, San Francisco, CA 94115, USA; study. and it is not an easy one. Controlling [email protected] time of onset of haemangioma, size, I believe that a different reason exists location, degree of astigmatism at out- for the relative scientific neglect of set, premature status, and presence or REFERENCES haemangioma and for the low number absence of intermittent occlusion are 1 Silverman WA. Missing and unaccounted for. of controlled clinical trials on this just a few of the issues. All of these Paediatr Perinat Epidemiol 2004;18:95–6. 2 Holmdahl K. Cutaneous hemangiomas in subject. The tumour is protean, its variables could be controlled in a premature and mature infants. Acta Paediatr biology and growth variable, and its large enough trial with, perhaps, a 1955;44:370–4.

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Childhood viewing in between times. Also, Chung ...... and colleagues6 undercorrected both eyes of a group of 47 young myopes, by approximately +0.75 D. After 2 years, Monovision slows myopia progression instead of the myopic blur these chil- dren having been exposed to making J A Guggenheim, C H To them less myopic, Chung et al found that the children had become even more ...... myopic than a control group who had Increased chances of finding an effective optical method of been fully corrected. So perhaps humans are unusual, in not being able to arresting myopia development emmetropise in response to defocus? Or perhaps by the time they reach n The Marriage of Heaven and Hell, negative spectacle lenses, which would school age, the plasticity of the human William Blake says that ‘‘If the doors have diverged the light entering the eye emmetropisation system has decreased Iof perception were cleansed every- and shifted the image plane behind the below a clinically significant level? thing would appear to man as it is: (leading to ‘‘hyperopic defocus’’) Even before the study by Phillips, infinite.’’ In vision, of course, there is a induced myopia. Meanwhile, positive however, there was indirect evidence simple connection between optical infi- spectacle lenses, which would have that exposure to blur could influence nity and perceived visual clarity, at least converged the light entering the eye, refractive development in school age for distance vision in emmetropes. shifting the image plane in front of the children. In the COMET study, a rando- Contact lens practitioners and refractive retina (producing ‘‘myopic defocus’’) mised, multicentre, double masked clin- surgeons have taken things one step induced hyperopia. In each case, the ical trial to evaluate whether progressive further. By exploiting the brain’s ability refractive change was mostly the result addition lenses (PALs) slowed myopia to perceptually suppress central vision of an altered rate of vitreous chamber development in children, PALs were in one eye when the two eyes are elongation. Chicks becoming myopic indeed found to slow myopia progres- receiving disparate stimuli, they have showed an acceleration in their normal sion significantly, though only by about found that it is often possible to correct rate of axial eye growth. Chicks devel- 14% over 3 years. While it is possible presbyopic ametropes using a distance oping hyperopia showed a slowing or that reduced itself was correction for the dominant eye, and a cessation of the normal rate. Similarly responsible for this slowed rate of near correction for the non-dominant elegant experiments have demonstrated progression, it seems more likely to have eye. In this ‘‘monovision’’ situation, that refractive plasticity of this kind, been the reduction in hyperopic defocus patients thus have to suppress the which represents an active form of brought about by the extra plus power central vision in their non-dominant emmetropisation, is a feature of the at near lessening the stimulus for eye for distance tasks, and in their early development of many other spe- myopia development, since in the sub- dominant eye for near tasks. cies, including marmosets2 and mon- group of children who had larger lags of In essence, monovision is a form of keys.3 accommodation, PALs slowed myopia deliberately introduced , So it seems highly likely that human progression to a greater extent (by 21% and it is this property that John Phillips infants also use blur cues to guide in general, and by 37% in children who has exploited in a highly original study, refractive development during emme- also had esophoria at near).7 in this issue of BJO (p 1196), that tropisation. What is less clear is whether How does the monovision study provides new insight into the role of blur contributes to the development of carried out by Phillips add to our blur in regulating eye growth and myopia in school aged children, as well. knowledge? Crucially, unlike presbyopic refractive development in children. In A decade ago, Gwiazda and colleagues4 monovision wearers, the children in the this small clinical trial, children received hypothesised that the lag of accommo- Phillips study were found to posture a full myopic correction for their domi- dation at near could explain the intri- their accommodation according to their nant eye and an undercorrection of up guing link between near work and dominant eye, for both distance and to +2.00 D for their non-dominant eye myopia. Children with an accommoda- near. This meant that the non-dominant (as discussed below, the undercorrec- tive lag at near would experience eye would have experienced myopic blur tion led to the vision in the children’s hyperopic blur at the retina that, accord- in both viewing conditions, and hence non-dominant eyes being continually ing to the animal models, would lead to throughout the period of spectacle wear. blurred). The results were striking: the myopia development. However, conclu- However, the amount of accommoda- rate of myopia progression in the under- sive proof for this theory is lacking, and tion these children exerted would pre- corrected eye was found to be approxi- more recent results from a longitudinal sumably have been similar to that when mately 50% of that in the fully corrected study suggest that there is no difference wearing a full distance correction. eye. Furthermore, the reduced rate of in accommodative lag before the onset Therefore, the new study strongly sug- myopic progression was attributed to a of myopia development, between those gests that it was the continuous myopic reduced rate of vitreous chamber elon- children who remain emmetropic and blur experienced by the undercorrected gation, consistent with a slowing of the those who become myopic.5 eye that signalled its slower rate of primary structural change responsible Furthermore, experiments in which myopic progression. for causing myopia. animals have been allowed short periods Critics might argue that the study by Using the chicken as a model, (minutes) of unrestricted vision, in Phillips is too small to get overly excited Schaeffel and co-workers1 first showed between long periods of hyperopic defo- about; after all only 13 children were that refractive state could be altered in cus, show that these intervals of sharp involved in the trial. Yet the ‘‘within response to retinal blur imposed by focus quickly counteract the tendency subject’’ design afforded by the mono- wearing a spectacle lens over one or towards myopia. This might mean that vision approach (compared to the both eyes. Remarkably, the change in children undergoing even prolonged ‘‘between subject’’ design necessitated refractive error Schaeffel et al found periods of near work induced blur are by myopia control trials such as the depended on the sign of the defocus: protected from myopia by distance COMET study) meant that despite its

www.bjophthalmol.com Downloaded from bjo.bmjjournals.com on 8 September 2005 EDITORIAL 1077 small size, the study was adequately effective. It should noted, as well, that if arresting myopia development look sig- powered, as the results confirm. a 50% reduction in myopia progression nificantly brighter. However, the lack of a control group turns out to be the best that can be Br J Ophthalmol 2005;89:1076–1077. does leave open room for a slight doubt: achieved, then taking into account the doi: 10.1136/bjo.2005.068106 because we do not know what the fact that the undercorrection would only baseline rate of myopia progression is be present for 50% of the time, then the ...... in this particular group of children, it is overall progression rate might be slowed Authors’ affiliations conceivable that the fully corrected eyes by only 25%, which would be disap- J A Guggenheim, School of Optometry and had shown an accelerated rate of myo- pointing. Vision Sciences, Cardiff University, King pia progression, rather than the under- Why should the undercorrected eyes Edward VII Avenue, Cardiff CF10 3NB, UK corrected eyes having shown a slower have become more myopic, despite the C H To, Department of Optometry and rate of progression. myopic blur they were exposed to? At Radiography, Hong Kong Polytechnic The new study immediately brings to this age, the eye is normally elongating University, Hung Hom, Hong Kong mind two key questions. Firstly, is it at approximately 0.2 mm per year,8 so possible to exploit this monovision there may be an endogenous, develop- Correspondence to: Jez Guggenheim, Cardiff University, King Edward VII Avenue, Cardiff paradigm clinically to slow myopia mental push towards axial elongation. CF10 3NB, UK; [email protected] progression? And, secondly, why did However, in animal models, visual cues Competing interests: none declared the undercorrected eyes still progress are generally able to dominate this towards myopia, instead of halting their innate propensity, to effectively halt progression completely? axial elongation completely. Table 1 of REFERENCES In answer to the first question, it is Phillips’s paper shows that there was 1 Schaeffel F, Glasser A, Howland HC. important to emphasise that the proto- some intersubject variation in response, Accommodation, refractive error and eye growth col used by Phillips induced anisome- and an impression that full time mono- in chickens. Vis Res 1988;28:639–57. tropia, because only the non-dominant vision wearers may have derived a 2 Graham B, Judge SJ. The effects of spectacle wear eye was exposed to myopic blur. slightly greater benefit than part-time in infancy on eye growth and refractive error in the marmoset (Callithrix jacchus). Vis Res Therefore, clinically, some kind of per- wearers. If so, then at least part of the 1999;39:189–206. iodic reversal of the treatment regimen explanation may be that during periods 3 Hung L-F, Crawford MLJ, Smith EL III. Spectacle would be required, so that the dominant when the monovision correction was lenses alter eye growth and the refractive status of young monkeys. Nat Med 1995;1:761–5. eye also spent time exposed to myopic not worn, the non-dominant eyes 4 Gwiazda J, Thorn F, Bauer J, et al. Myopic blur while the non-dominant eye experienced hyperopic defocus (either children show insufficient accommodative received clear vision. A crucial issue is because of children reverting to a con- response to blur. Invest Ophthalmol Vis Sci 1993;34:690–4. whether children will tolerate the ventional spectacle correction, or doing 5 Mutti DO, Mitchell GL, Jones LA, et al. undercorrection of their dominant eyes near work while uncorrected). Accommodative lag at the onset of myopia in in the reversed monovision situation. If Alternatively, there may be additional children. Invest Ophthalmol Vis Sci 2004;45:E- 3514. they do, then the prospects look promis- environmental risk factors for myopia 6 Chung K, Mohidin N, O’Leary DJ. 9 ing, but much work will still be required progression to which these children Undercorrection of myopia enhances rather than to optimise the treatment. For instance, were exposed, or it could be that once inhibits myopia progression. Vis Res 2002;42:2555–9. would greater amounts of blur give a myopia progression has begun, that it is 7 Gwiazda JE, Hyman L, Norton TT, et al. stronger effect, or would this tip the somehow self perpetuating (there is a Accommodation and related risk factors balance and induce form deprivation precedent for this in marmosets10). associated with myopia progression and their myopia? What would be the optimal In conclusion, by providing evidence interaction with treatment in COMET children. Invest Ophthalmol Vis Sci 2004;45:2143–51. treatment duration—for example, that further implicates blur in driving 8 Larsen JS. The sagittal growth of the eye. IV. would it be better to switch the under- the progression of myopia in school age Ultrasonic measurement of the axial length of the correction on alternate days, alternate children and, most importantly, in eye from birth to puberty. Acta Ophthalmol 1971;49:873–86. weeks, or alternate months, perhaps? providing arguably the strongest evi- 9 Saw S-M, Katz J, Schein OD, et al. Epidemiology Also, a more rigorous study design, dence yet that myopia progression can of myopia. Epidemiol Rev 1996;18:175–87. including masked observers and a fully be slowed by imposing myopic blur at 10 Troilo D, Judge SJ. Ocular development and visual deprivation myopia in the common corrected control group will be required the retina, this study makes the chances marmoset (Callithrix jacchus). Vis Res to prove conclusively that monovision is of finding an effective optical method of 1993;33:1311–24.

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