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Author's response to Spectral-domain optical coherence tomography in subjects over 60 years of age, and its implications for designing clinical trials
  1. Albert Caramoy
  1. Department of Ophthalmology, University of Cologne, Cologne, Germany
  1. Correspondence to Dr Albert Caramoy, Department of Ophthalmology, University of Cologne, Kerpenerstr. 62, Cologne 50924, Germany; acaramoy{at}yahoo.co.uk

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I would like to thank Comyn et al for their interest in our published article.1 I agree that different methodologies, different assumptions, or even analyses on different patient collectives might result in a different conclusion or a different sample size needed for randomised clinical trials.

(i and ii) Power: the sample size calculation used with power of 80% was based on studies, such as the Age-Related Eye Disease Study trial.2 Using 90% power, α=0.05 and 10% loss to follow-up, I calculated once more the sample size needed for hypothetical studies (table 1).

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Table 1

Sample size calculations

(iii) I integrated the findings from Comyn …

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