Skip to main content
. Author manuscript; available in PMC: 2015 Jan 10.
Published in final edited form as: Cochrane Database Syst Rev. 2013 Oct 23;10:CD003303. doi: 10.1002/14651858.CD003303.pub3

Peterson 2003.

Methods Method of allocation: Each magnifying device was presented in a random order to participants; theywere asked to complete (also in a randomorder) a series of 4 tests chosen specifically to replicate daily living tasks. Methods of randomisation are not described.
Masking: Participant -masking issues are not described but the study should be unmasked given the use of recognisable devices. Provider - same as above; Outcome - same as above Exclusions after randomisation: none reported.
Losses to follow-up: none reported.
Unusual study design: Within-subject design, i.e. a cross-over study in which all participants try the devices consecutively
Participants Country: UK
Number randomised: 70
Age, Sex: 35 men with mean age: 68.3 (SD: 22.8) years and 35 women with mean age: 71.8 (SD: 20.6) years.
Inclusion criteria: consecutive visually impaired participants. Each had previously undergone ophthalmologic care and a full low-vision examination including optimization of their refraction and their optical magnifier. Minimum magnification for comfortable reading of the participants' chosen print size was prescribed.
Exclusion criteria: none.
Interventions Treatment: various electronic vision enhancement systems (EVES) vs the subject's optimum conventional optical magnifier for near task. Optical magnifiers were a hand magnifier (n. 24), a stand magnifier (n. 45), and high-powered reading glasses (n. 1) with an average nominal magnification (lens dioptric power divided by 4) of 5.7 times (range, 2.0 - 14.7 times). EVES were:

  1. mouse-based with the image viewed at a fixed distance of 40 cm on a 14” monitor;

  2. mouse-based with the image viewed on a HMD unit;

  3. stand-based EVES with the image viewed at a fixed distance of 40 cm on a 14” monitor (images were black on white)
Outcomes After an explanation, demonstration and a 2-minute active training period with each magnifying device the participants were asked to complete a series of 4 tests chosen to replicate daily living tasks:

  1. Reading speed and acuity (using adapted MNREAD charts);

  2. Time taken to track from 1 column of print to the next;

  3. Time taken to follow a route on a map and locate a specific feature;

  4. Time taken to identify specific information from a medicine bottle label.


4 versions of each task, equal in difficulty (in terms of number, length, and difficulty of words and page distance), were constructed and used in a randomised order to control fatigue effects
Notes
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Randomised presentation of devices; although no further detail was given on how the randomisation sequence was generated, selection bias should be avoided since all participants used all devices (crossover study design)
Allocation concealment (selection bias) Low risk Randomised presentation of devices; although no further detail was given on how randomisation sequence was concealed, selection bias was likely to be avoided since all participants used all devices (cross-over study design)
Incomplete outcome data (attrition bias) All outcomes High risk Not all participants could read using all devices; thus, the analysis is not intention-to-treat
Selective reporting (reporting bias) Low risk No protocol available, but primary outcome reported
Period effect Unclear risk No details reported
Carry-over effect and period-by-treatment interaction Unclear risk Authors reported they used reading and real-word tests of very short duration, but no quantitative details are available
Other bias Low risk No other bias identified