Methodological quality of the review: High confidence
Author: Virgili G, Acosta R, Grover LL, Bentley SA, Giacomelli G
Region: United Kingdom (UK) and United States of America (USA).
Sector: Reading aids
Sub-sector: Low vision rehabilitation, electronic devices, optical magnifiers.
Equity focus: Adults aged 16 or over
Review type: Effectiveness review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis methods: Not applicable
The number of people with low vision is increasing with the aging population. Rehabilitation of low vision among the population has therefore become more relevant. The purpose of low-vision rehabilitation is to allow people to resume or to continue to perform daily living tasks, with reading being one of the most important. This is achieved by providing appropriate optical devices and special training in the use of residual-vision and low-vision aids, which range from simple optical magnifiers to high-magnification video magnifiers.
To provide evidence on the effect of reading aids on reading ability in people with low vision, and to investigating whether there are differences in reading performance using conventional optical devices, such as hand-held or stand-based microscopic magnifiers, as compared to telescopic optical devices, or electronic devices such as stand-based, closed-circuit television and hand-held electronic magnifiers.
The authors included nine small studies with a crossover-like design (181 people overall) and one study with three parallel arms (243 participants) in the review. All studies reported the primary outcome as results for reading speed.
Two studies including 92 participants found moderate- or low-quality evidence suggesting that reading speed is higher with stand-mounted electronic devices or electronic devices with the camera mounted in a ‘mouse’ than with optical magnifiers, which in these trials were generally stand-mounted or, less frequently, hand-held magnifiers or microscopic lenses. In another study of 20 participants there was moderate-quality evidence that optical devices are better than head-mounted electronic devices (four types).
There was low-quality evidence from three studies (93 participants) that reading using head-mounted electronic devices is slower than with stand-based electronic devices. The technology of electronic devices may have changed and improved since these studies were conducted.
One study suggested no difference between a diffractive spectacle-mounted magnifier and either refractive (15 participants) or aplanatic (15 participants) magnifiers.
One study of 10 people suggested that several overlay coloured filters were no better and possibly worse than a clear filter.
A parallel-arm study including 243 participants with age-related macular degeneration found that custom or standard prism spectacles were no different from conventional reading spectacles, although the data did not allow precise estimates of performance to be made.
The authors concluded that there was insufficient evidence on the effect of different types of low-vision aids on reading performance. Therefore, it would be necessary to investigate which patient characteristics predict performance with different devices, including costly electronic devices. Reviewers also noted that better quality research should also focus on assessing sustained long-term use of each device; and authors of studies testing several devices should consider design and reporting issues related to their sequential and to the crossover-like study design.
The authors included randomized and quasi-randomized trials that included participants aged 16 years or over with low vision in which a device or aid used for reading visually was compared to another device or aid. Primary outcome measure for this updated version was reading speed in words per minute, recorded using typical point size, in books or newspapers.
The authors searched the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, LILACS, OpenGrey (System for Information on Grey Literature in Europe), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP). No date or language restrictions were applied in searches for trials. As part of the search strategy authors also reviewed reference lists of relevant studies and used the Science Citation Index to find articles that cited the included studies and contacted investigators and manufacturers of low-vision aids to identify other published and unpublished reports.
Two authors independently assessed the titles and abstracts to determine study eligibility for inclusion, extracted data and assessed quality and risk of bias of included studies.
The authors conducted a meta-analysis using the following methods: for dichotomous data, results were expressed as odds ratio (OR) estimates or risk ratio (RR) estimates (with a 95% confidence interval). Participants, rather than eyes, are the unit of analysis in this review.
For future updates of this review, as long as a sufficient number of studies were found, the authors noted that they would assess heterogeneity using the I2 statistic and its 95% confidence interval and conduct sensitivity analysis.
The authors noted that sample sizes were small, being less than 40 participants in all but one crossover-like study and one parallel-arm study. No study reported the sample size calculation. However, as authors noted, the gain in power is counterbalanced by a number of potential issues, including generalizability of the findings if conducted using a small sample of homogeneous participants.
Although the authors did not restrict the search to specific income settings, only high-income country studies were eligible for inclusion in the review. Authors did not discuss the applicability of the results related to low and middle income settings as evidence reported by included studies were inconclusive.
Overall, there is high confidence in the conclusions about the effects of this study. The authors conducted a comprehensive search of published and unpublished literature to ensure that all relevant trials were included in the review, avoiding language bias. They used appropriate methods in terms of study selection, data extraction and quality assessment of included studies, minimizing the risk of bias. Limitations of included studies were acknowledged and due to the lack of evidence no strong policy conclusions were drawn by the authors.