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Abstract #92660 Published in IGR 22-1
Improving the Power of Glaucoma Neuroprotection Trials Using Existing Visual Field Data
Montesano G; Quigley HA; Crabb DPAmerican Journal of Ophthalmology 2021; 229: 127-136
PURPOSE: Selecting reliable visual field (VF) test takers could improve the power of randomized clinical trials in glaucoma. We test this hypothesis via simulations using a large real world data set. DESIGN METHODOLOGY ANALYSIS: assessment of how improving reliability affects sample size estimates. METHODS: A variability index (VI) estimating intertest variability was calculated for each subject using the residuals of the regression of the mean deviation over time for the first 6 tests in a series of at least 10 examinations for 2,804 patients. Using data from the rest of the series, we simulate VFs at regular intervals for 2 years. To simulate the neuroprotective effect (NE), we reduced the observed progression rate by 20%, 30%, or 50%. The main outcome measure was the sample size to detect a significant difference (P < .05) at 80% power. RESULTS: In the first experiment, we simulated a trial including one eye per subject, either selecting randomly from the database or prioritizing patients with low VI. We could not reach 80% power for the low NE with the available patients, but the sample size was reduced by 38% and 49% for the 30% and 50% NE, respectively. In the second experiment, we simulated 2 eyes per subject, one of which was the control eye. The sample size (smaller overall) was reduced by 26% and 38% for the 30% and 50% NE by prioritizing patients with low VI. CONCLUSIONS: Selecting patients with low intertest variability can significantly improve the power and reduce the sample size needed in a trial.
City, University of London Optometry and Visual Sciences (G.M., D.P.C.), London, United Kingdom; NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology (G.M.), London, United Kingdom.
Full articleClassification:
11.8 Neuroprotection (Part of: 11 Medical treatment)
6.6.2 Automated (Part of: 6 Clinical examination methods > 6.6 Visual field examination and other visual function tests)