7 Screening older people for impaired vision

Background

There are a number of factors that make visual impairment among older people an attractive target for screening. Visual impairment is common, causes substantial disability, is easy to diagnose, and many people’s vision could be improved with treatment. A recent survey in the United Kingdom found bilateral visual acuity of less than 6/12 in around 30% of people aged 65 or more,1 over 70% of which was considered potentially remediable. Only 12% of older people with a cataract causing impaired vision were in touch with eye care services and only one-third of those with substantial uncorrected refractive error had seen an optometrist in the past 12 months.1 Comparable results have been found in other surveys undertaken in other developed countries.2–5 Visual impairment has been reported as having physical, psychological and social ramifications. For example, functional status, social contacts and quality of life are lower.6–12 Furthermore, visual impairment has been shown to be strongly associated with depression10,13 falls and hip fractures.14–17

In practice, screening for visual impairment is only likely to be one part of a broader package of screening measures, an approach commonly referred to as a multidimensional screening assessment.18 Most forms of assessment include some attempt to assess vision.

Question

What is the effectiveness of mass screening for visual impairment in unselected older people (65 and over) in a community setting, either alone or as part of a regular multidimensional assessment programme?

The evidence

A systematic review of randomised controlled trials of mass screening of older people for visual impairment is included in the Cochrane Library.19 The review included all randomised controlled trials of population based screening for visual impairment (using any screening method) in a

community setting in people aged 65 or over. The outcomes used were the risk of visual impairment (however measured) in the population at the end of the trial. Although screening for visual impairment may have other beneficial effects, such as reducing falls or improving quality of life, any such improvement would be a result of improving vision.

The review found five randomied trials that included a total of 3494 participants.20–24 All trials were of multidimensional screening with vision screening as one component. There were no trials that primarily assessed visual screening. Allocation concealment was adequate in all trials. Because of the nature of the intervention, it would not have been possible to mask either recipients or providers of care to their allocation.

The results in all five trials were similar (Figure 7.1). There was no evidence of heterogeneity of effect between the five trials. The pooled relative risk for self-reported visual problems at the time of outcome assessment (range two to four years after the screening assessment) comparing the intervention and control groups was 1·03 (95% CI 0·92–1·16). The pooled odds ratio was 1·04 (95% CI 0·89–1·22).

Discussion

Given that visual impairment is common, disabling, frequently unreported, and often treatable, the lack of improvement in vision seen in these trials is somewhat surprising. A screening procedure alone would not be expected to lead to improvements in vision. Such improvements would be dependent on subsequent interventions to improve vision. The trial reports did not include information about whether screening improved the detection of treatable visual impairment or about the subsequent management of the visual problems detected. In addition, the use of questions about vision both for the initial screening assessment and for the outcome assessment may have affected the results. The sensitivity of questions about vision for the detection of visual impairment is typically around 30% when compared to formal acuity

testing.25 Although the specificity is generally much higher, the low sensitivity of the tests used means that many people’s visual impairment would not have been detected by screening.

Implications for practice and policy

The aim of population screening of older people for visual impairment is to identify people with potentially treatable visual impairment that is hitherto undetected and to offer interventions to improve vision. The evidence from randomised controlled trials undertaken to date does not currently support the inclusion of questions about vision in regular multidimensional assessment programmes for unselected older people in a community setting. Although a reduction of 8% in the number of older people with visual impairment cannot be excluded, even this figure is disappointingly low.

Implications for research

In practice, screening for visual impairment is highly likely to be one part of a broader screening package. A large randomised trial of screening older people for visual impairment as part of a broader screening assessment, which overcomes the possible limitations of the trials undertaken to date, is warranted. A trial funded by the United Kingdom Medical Research Council is currently underway, and results will be available in late 2003. Further details are available from the chapter author.

References

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Why does this section focus on ophthalmic disorders specific to children? First, because anatomical and physiological changes occur throughout childhood in the developing visual system. Therefore, the nature and impact of visual loss in children differs from adults, with visual impairment in childhood having important consequences for all aspects of a child’s development, their education and their care by family and professionals. Second, many visually impairing paediatric disorders are specific to children and those that are not often have different functional effects in children compared to adults. Third, as a high proportion of visually impaired children have other significant sensory, motor or learning impairments, visual loss needs to be considered in this broader context.

There are particular difficulties in undertaking clinical trials of childhood eye diseases. Most visually impairing disorders are individually rare, necessitating large, collaborative multi-centre studies that are difficult and expensive to undertake. Although many disorders are present from early childhood, visual maturation is not complete until much later. Therefore important outcomes can only be reliably determined through long-term followup, which is difficult to achieve. Finally, there a number of

ethical considerations about children’s participation in trials, which are the subject of ongoing debate, that do not arise with adult subjects able to consent to participation themselves. Although these potential obstacles are important, they only partly account for the limited extent to which paediatric ophthalmic practice is currently based on evidence from high-quality randomised controlled trials.

The aims of this section are to describe the available evidence from trials (from the Cochrane Eyes and Vision Group (CEVG) register and published systematic reviews of trials), as well as to highlight the areas where evidence is lacking, and to identify the important questions that have yet to be addressed.

The section comprises chapters on those disorders most commonly encountered in paediatric ophthalmic practice (amblyopia and strabismus) as well as on the major, and preventable or treatable, visually impairing disorders congenital cataract, retinopathy of prematurity, congenital glaucoma and ophthalmia neonatorum). Other important disorders affecting children are addressed in the sections on adnexal disease (lacrimal obstruction), uveitis (toxoplasma and toxocara infection) and oncology (retinoblastoma).