Vision screening in children

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In his article in the current issue of Deutsches Ärzteblatt International (Dtsch Arztebl Int 2010; 107[28-29]: 495-9), Wolf A. Lagrèze examines whether or not childhood screening for vision disorders in preschool children is worthwhile.

Eye disorders can occur even in very young children and may threaten their vision. Retinopathy of prematurity is currently the only eye disorder for which ophthalmological screening is provided in Germany. Childhood screening for other eye disorders would also be worthwhile if the disorder to be diagnosed were sufficiently common and successful treatment guaranteed.

Amblyopia is defined as a unilateral sight disorder that can weaken the affected eye or the visual apparatus as a whole. Strabismus, for example, hinders visual development and can be treated by temporarily covering the better eye. The most significant study conducted to date tested 6081 seven-year-olds and found that those who had been screened and treated as preschoolers developed visual problems somewhat less frequently than those who had not. The frequency of visual disorders also seems to be correlated to membership of certain social strata.

German law establishes vision screening as part of routine childhood examination. However, as not all the doctors who carry out such examination currently receive sufficient training, and as their remuneration is often too low to cover their costs, the program is probably unable to provide what the law establishes.

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SUMMARY

Background: Comprehensive, systematic reviews on the benefit of vision screening in preschool children were published in 2008 by major national organizations in both Germany and the United Kingdom. These reviews raised public interest in the topic.

Methods: This article contains a discussion of the sensitivity, specificity, efficacy, and cost-effectiveness of preschool vision screening, on the basis of the two national reports mentioned above as well as relevant literature retrieved by a selective PubMed search.

Results: All studies that have been published to date on the efficacy of preschool visual screening suffer from methodological flaws. The avail able data suggest a benefit from screening, though this has not been proven. Model calculations reveal that the positive predictive value of screening tests performed in isolation is inadequate. 

The authors of the two national reports applied different methods and arrived at similar, but not identical conclusions.

Preschool vision screening may also be cost-effective; whether this is the case or not depends on the probability of a long-term benefit—specifically, on the probability of preventing bilateral loss of vision in adulthood. To prevent one such case, it is estimated that 13 cases of childhood amblyopia must be identified and successfully treated (number needed to treat [NNT] = 13).

Conclusion: The available data do not allow any firm conclusion about the efficacy and cost-effectiveness of preschool vision screening. Fur ther clinical studies are needed to answer these questions.

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To determine whether or not universal vision screening in preschool children is worthwhile, we must establish whether it reduces the prevalence of sight disorders and what the cost of testing is. 

These matters gained renewed public attention after the Joint Federal Committee commissioned the German Institute for Quality and Efficiency in Health Care (IQWiG) to compile a report on the subject, which was published in 2008 (1). A few months later, the UK’s National Institute of Health Research published a work with a similar scope, in the form of a Health Technology Assessment (HTA) (2).  This article aims to address the questions posed and summarize the current status of research. To do so, both the above-mentioned reports and the results of a selective PubMed literature search have been analyzed and evaluated.

The range of eye disorders in children
The Table shows how often various eye disorders occur in children, in relation to the number of children born in a given year. The sight-threatening disorders of the first few months of life include the following:

• Congenital cataracts
  
• Congenital glaucoma
  
• Retinoblastoma
  
• Retinopathy of prematurity.

Although these disorders are rare, they are often bilateral and lead to severe visual impairment if not swiftly treated. Retinopathy of prematurity is the only eye disorder for which there is selective ophthalmological screening in Germany if there is an increased risk of the disorder due to premature birth (3).

Amblyopia is one of the most common disorders in the first few years of life and is usually caused by ametropias (e.g.  far-sightedness, astigmatism) or strabismus. Pathogenetically, amblyopia hinders the development of vision during the “sensitive phase” in the first few years of life, as a result of the following:

• Strabismus
  
• Ametropias
  
• Optical deprivation.

During this phase, amblyopia can be successfully treated by temporarily covering the better eye (occlusion therapy), prescribing glasses, or possibly operating (4).

Among other cases, screening is worthwhile when the disorder to be diagnosed is sufficiently common and successful treatment is guaranteed (5).  Preschool visual screening therefore aims primarily to prevent amblyopia by identifying its main causes early on. At the same time, however, other, rarer but possibly more serious eye disorders might also be diagnosed, depending on the methods used. The figures in the literature for the prevalence of amblyopia range from 1% (6) to 5.3% (7).  This variation can be explained by differences in the cohorts examined and the lack of a binding definition of amblyopia.

The current situation
German law establishes exploratory vision screening as part of routine childhood medical examinations.  The statutory health insurance scheme allows for children to be screened if there is reason to suspect a vision disorder. It covers ophthalmological examination only if a disorder has been found. Remuneration for this is currently less than 20 euros per quarter. A pediatrician or family doctor may claim approximately 35 euros for all routine childhood examinations, but in return for this sum must provide a full somatic, neurological and developmental psychology report. Nine of the ten routine examinations include examination of the visual apparatus. For example, examination 5, which is carried out at six months, examines the following parameters:

• Fixation
  
• Ocular motility
  
• Eye position
  
• Pupil reactions
  
• Tear duct function
  
• Diameter of cornea
• Other eyeball abnormalities.

As the doctors carrying out examinations do not currently receive specific training for this, and as the remuneration for these measures is too low to cover the cost of the time required, we can conclude that the program is unable to provide what the law establishes.

The sensitivity of routine childhood medical examinations was ascertained as part of a study sponsored by the Bertelsmann Foundation.  665 preschool children aged 3.5 to 4.5 years underwent ophthalmological and orthoptic examination.  28% of the children displayed abnormalities. 70% of these were not classified as “disorders” in routine medical examinations (8). The German Pediatricians’ Association and Ophthalmologists’ Association have repeatedly pointed out flaws in the system.

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Wolf A. Lagrèze

Contact: Dr. Wolf Lagreze

Deutsches Aerzteblatt International

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