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Author's reply
Submit responseDear Editor,In a reply to my editorial in the November issue, Dr Lempert raises several valid concerns regarding vision screening for amblyopia. I would like to thank Dr Lempert for his reply and this possibility for a discussion on a difficult and important topic!
I was, however, slightly surprised to find that the reply is written as a rebuttal of my arguments, while I am of the same opinion as Dr Lempert, and have tried to express this in the editorial!
In the first paragraph Dr Lempert cautions against assuming that treatment for amblyopia normalizes visual function. I absolutely agree, and in my editorial I explicitly state: “There is a clear need for objective studies on the possible relationship between unilateral amblyopia and functional disabilities. In such studies, comparisons should be made between three groups: (1) normal controls, (2) non-treated amblyopes, and (3) amblyopes after successful treatment.”
Dr Lempert claims that my editorial “implies that lack of screening and treatment of amblyopia cause a lifelong handicap.” I have never intended to say this, and even find it slightly amusing, since I have countless times been accused of being “anti-screening” when pointing out that we currently do not have evidence to be able say that untreated unilateral amblyopia is disabling! I write “In discussing the rationale for preschool vision screening programmes, more results on possible associations between amblyopia and increased lifetime risk of visual impairment, as well as quality of life/utility measures for unilateral amblyopia, are required.”
Dr Lempert also claims my editorial implies that “treatment offers a significant cost / benefit gain.” I do report on results from previously published papers 1, 2, however, results showing that treatment for spontaneously presenting amblyopia (which these two papers deal with) is cost-efficient must not be confused with evidence for vision screening being cost-efficient!
In the final paragraph Dr Lempert points to the need for effective allocation of medical resources. I, again, agree, and have written in my editorial: “In a world with limited economic resources and ever-growing expenses for medical services, we will most likely see an increasing demand for evaluation, evidence of benefit and proof of cost-effectiveness for government-financed screening programmes.”
I still do believe that van Leeuwen’s paper3 is a very important contribution, and as I conclude my editorial: “As of today, we do not have all of the information required, but van Leewen et al’s work has provided us with very valuable data, moving us closer to determining whether preschool vision screening can be justified.”
Respectfully submitted,
Josefin Nilsson (née Ohlsson), MD, PhDReferences
1. Membreno JH, Brown MM, Brown GC, Sharma S, Beauchamp GR. A cost-utility analysis of therapy for amblyopia. Ophthalmology 2002;109:2265-71.
2. König HH, Barry JC. Cost effectiveness of treatment for amblyopia: an analysis based on a probabilistic Markov model. Br J Ophthalmol 2004;88:606-12.
3. van Leewen R, Eijkemans M, Vingerling JR, Hofman A, de Jong P, Simonsz HJ. Risk of bilateral visual impairment in persons with amblyopia: The Rotterdam Study. Br J Ophthalmol 2007;91:1450-1. -
Amblyopia and visual function
Submit responseRe: van Leeuwen R, Eijkemans MJC, Vingerling JR, Hofman A, de Jong PTVM, Simonsz HJ Risk of bilateral visual impairment in individuals with amblyopia: the Rotterdam study BJO 2007;91 (11): 1450
Josefin Nilsson The negative impact of amblyopia from a population perspective: untreated amblyopia almost doubles the lifetime risk of bilateral visual impairment. BJO 2007;91 (11): 1417
Dear Editor
It is not surprising that amblyopes are at higher risk of bilateral visual impairment since impaired visual functions of the fellow eye have been previously demonstrated. Leguire et al warned that “In future studies of amblyopia, whether in children or in adults, caution is advised in assuming that the nonamblyopic eye is normal because acuity is normal.” [2] Johnson found that both amblyopic and fellow eyes had central scotomata, even after apparently successful treatment, [3] and concluded that “ocular effects of amblyopia may not be strictly limited to the amblyopic eye.” [4] Anomalous optic discs, reduced axial lengths,[5] and anatomic abnormalities involving the axial length to optic disc area have been reported as present to different degrees in amblyopic and fellow eyes.[6,7] Moreover, amblyopia is commonly associated with systemic disorders such as prematurity and low birth weight[8] even in the absence of retinopathy. [9] These anatomic and functional factors put both eyes at risk makes them more susceptible to vision loss.
Nilsson’s editorial implies that lack of screening and treatment of amblyopia cause a lifelong handicap[10] and that treatment offer a significant cost / benefit gain.[11,12] These beliefs employed several unsupported assumptions. Among them is that treatment results in final visual acuity sufficient to perform all tasks and that untreated amblyopia has a financial handicap equivalent to workman’s compensation scales for loss of an eye. Actually, treatment of severe amblyopia rarely results in functionally useful vision.[13] PEDIG studies showed that approximately 25 percent of their treated patients had no or very limited improvement at the end of their initial observation period.[14,15] Initial successes were reduced by an anticipated 50 percent rate of recidivism.[16,17] Furthermore, the assumption that improved Snellen acuity reflects functional improvement is challenged by findings that reading speed is significantly less than normal even when final acuity was comparable with the controls. [18]
A retrospective demographic investigation concluded that “No functionally or clinically significant differences existed between people with and without amblyopia in educational outcomes, behavioral difficulties or social maladjustment, participation in social activities, unintended injuries (school, workplace, or road traffic accidents as driver), general or mental health and mortality, paid employment, or occupation based social class trajectories.”[19]
There is an absolute need for effective allocation of medical resources.[20] Increased bilateral vision impairment among people with initial anatomic ocular defects in both eyes must motivate efforts to prevent those prenatal conditions leading to impaired ocular anatomy.
Respectfully submitted, Philip Lempert, MD
References
1. van Leeuwen R, Eijkemans MJC, Vingerling JR, Hofman A, de Jong PTVM, Simonsz HJ Risk of bilateral visual impairment in individuals with amblyopia: the Rotterdam study BJO 2007;91 (11): 1450
2. Leguire LE, Rogers GL, Bremer DL Amblyopia: the normal eye is not normal. J Pediatr Ophthalmol Strabismus 1990;27(1):32-38
3. Johnson DA Relative scotomata in the "normal" eye of functionally patients. A scanning laser ophthalmoscope (SLO) micreperimetric study. Binocul Vis Strabismus Q. 2007;22(1):17-48.
4. Johnson DA The use of the scanning laser ophthalmoscope in the evaluation of amblyopia (an American Ophthalmological Society thesis). Trans Am Ophthalmol Soc. 2006;104:414-36.
5. Lempert P. Porter L. Dysversion of the optic disc and axial length measurements in a presumed amblyopic population J Amer Acad Ped Ophthalmol Strabismus 1998;2:207-213
6. Lempert P. Axial length – disc area ratio in esotropic amblyopia. Arch Ophthalmol 2003; 121:821-824
7. Lempert P The axial length / disc area ratio in anisometropic hyperopic amblyopia: A hypothesis for decreased unilateral vision associated with hyperopic anisometropia. Ophthalmology 2004:111:304-308
8. Holmström G, M el Azazi M, Kugelberg U Ophthalmological follow up of preterm infants: a population based, prospective study of visual acuity and strabismus Br J Ophthalmol 1999;83:143-150
9. O’Connor AR, Stephenson TJ, Johnson A, Tobin MJ, Ratib S, Moseley M, Fielder AR Visual function in low birthweight children . British Journal of Ophthalmology 2004: 88 (9): 1149 - 1153
10. Josefin Nilsson The negative impact of amblyopia from a population perspective: untreated amblyopia almost doubles the lifetime risk of bilateral visual impairment. BJO 2007;91 (11): 1417
11. Joish VN, Malone DC, Miller JM. A cost-benefit analysis of vision screening methods for preschoolers and school-age children. J AAPOS 2003;7:283-290
12. Membreno JH, Brown MM, Brown GC, Sharma S, Beauchamp GR. A cost- utility analysis of therapy for amblyopia.Ophthalmology. 2002;109(12):2265 -2271.
13. Ingram RM Amblyopia: the need for a new approach Brit J. Ophthalmol 1979:63:236-237
14. PEDIG A randomized trial of atropine vs. patching for treatment of moderate amblyopia in children. Arch Ophthalmol 2002;120:268-278
15. Pediatric Eye Disease Investigator Group. The course of moderate amblyopia treated with patching in children: experience of the amblyopia treatment study. Am J Ophthalmol. 2003;136(4):620-629
16. Simons K. Amblyopia characterization, treatment, and prophylaxis. Surv Ophthalmol. 2005;50(2):123-66
17. Rutstein RP, Fuhr PS Efficacy and stability of amblyopia therapy. Optom Vis Sci 1992;69(10):747-754
18.Stifter E, Burggasser G, Hirmann E, Thaler A, Radner W. Monocular and binocular reading performance in children with microstrabismic amblyopia. Br J Ophthalmol. 2005;89(10):1324-9
19. J S Rahi, P M Cumberland, and C S Peckham Does amblyopia affect educational, health, and social outcomes? Findings from 1958 British birth cohort BMJ 2006; 332: 820-825
20. Woolf SH Potential Health and Economic Consequences of Misplaced Priorities. JAMA 2007;197(5) 523-526 -
Re: Amblyopia and visual function
Submit responseDear Editor,
I appreciate the letter by Dr. Lempert regarding Dr. Nilsson's Editorial to our study of the extension of the period of bilateral visual impairment (BVI) in persons with untreated amblyopia, and the response by Dr. Nilsson. A slight misunderstanding may arise, however, from the first sentence of Dr. Lempert's letter: "It is not surprising that amblyopes are at higher risk of bilateral visual impairment since impaired visual functions of the fellow eye have been previously demonstrated."
This may seem to imply that we reported extension of the period of BVI caused by impaired function of the fellow eye. Instead, we reported that for untreated amblyopes the lifetime risk of BVI was 18% while they lived on average 7.2 years with BVI, while for non-amblyopes, these figures were 10% and 6.7 years, respectively. Hence, untreated amblyopia extended the average expected period living with BVI from 0.7 to 1.3 years. This extension was only or primarily caused by the fact that they already had decreased function of their amblyopic eye.
Respectfully submitted,
Herb Simonsz
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