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Improving on ETDRS acuities: design and results for a computerised thresholding device.
D A Rosser1, I E Murdoch, F W Fitzke
1Department of Epidemiology and International Eye Health Institute of Ophthalmology University College London London, UK. danrosser@bleyonder.co.uk
Eye (London, England)
|August 21, 2003
Summary
A new computerized system reduces test-retest variability (TRV) in visual acuity measurements. This advancement allows for earlier detection of clinical changes and improves statistical power in clinical trials.
Area of Science:
- Ophthalmology
- Clinical Research
- Biomedical Engineering
Background:
- Visual acuity data is prone to test-retest variability (TRV), impacting clinical trial power.
- Measurement errors obscure true clinical changes and reduce statistical significance.
Purpose of the Study:
- To assess if a computerized system can reduce TRV by averaging repeated visual acuity measurements.
- To compare the TRV of a novel computerized system (PC-test) against the ETDRS logMAR chart.
Main Methods:
- 19 subjects with varying visual acuity were recruited.
- Two computerized tests (averaging 10 and 5 repeats) were compared with the ETDRS logMAR chart.
- TRV and agreement of acuity data were analyzed.
Main Results:
- Computerized tests yielded lower TRV (+/-0.11 and +/-0.10 logMAR) compared to the ETDRS chart (+/-0.18 logMAR).
- No significant bias was found between PC-test and ETDRS acuities.
Conclusions:
- Computerized systems averaging repeated measurements show reduced TRV compared to single ETDRS measurements.
- Lower TRV facilitates earlier detection of clinical changes in patients.
- Reduced TRV enhances the ability to detect smaller group differences in clinical trials.