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Which endpoint: mean intraocular pressure or proportion of successful patients?
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Ophthalmology.
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Information Science, Statistics.
2003 (English)In: Journal of glaucoma, ISSN 1057-0829, E-ISSN 1536-481X, Vol. 12, no 4, 321-332 p.Article in journal (Refereed) Published
Abstract [en]

A reduction in intraocular pressure in clinical trials can be determined through the mean intraocular pressure, through the proportion of patients who have the intraocular pressure reduced to a specific target intraocular pressure, or both. Since both these possible endpoints measure the shift of 2 intraocular pressure distributions, we recommend that only one of them be tested. In general, testing the difference between mean-values is much more efficient than testing the difference between proportions. However, proportions of successful patients are valuable in showing the clinical implication of a reduction in mean intraocular pressure, particularly when evaluating a moderate pressure reduction. The effect of a small mean intraocular pressure reduction on the probability to reach the target intraocular pressure is pointed out, particularly the fact that it can be substantial even if the mean reduction is smaller than the measurement error.

Place, publisher, year, edition, pages
2003. Vol. 12, no 4, 321-332 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-90325PubMedID: 12897577OAI: oai:DiVA.org:uu-90325DiVA: diva2:162637
Available from: 2003-04-07 Created: 2003-04-07 Last updated: 2013-07-04Bibliographically approved
In thesis
1. Pooling Data from Similar Randomized Clinical Trials Comparing Latanoprost with Timolol; Medical Results and Statistical Aspects
Open this publication in new window or tab >>Pooling Data from Similar Randomized Clinical Trials Comparing Latanoprost with Timolol; Medical Results and Statistical Aspects
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Two different principles were studied. 1st - statistical analysis techniques were used to obtain medical results from a patient population. 2nd - the patient population was used to study the statistical analysis techniques.

Medical conclusions: latanoprost and timolol treatment showed a statistically significant and clinically useful mean IOP-reduction in a typical worldwide clinical trial population. Latanoprost reduced the IOP 1.6 mm Hg more than timolol. The IOP-reduction was maintained with timolol and slightly enforced with latanoprost up to 6 months of treatment. The mean IOP-reduction was maintained during 2 years of latanoprost treatment. The overall risk of withdrawal due to insufficient IOP-reduction with latanoprost was 8%.

The statistical methodological issues are of a general and reoccurring character in trial design of the IOP-reduction: should the statistical hypothesis testing be based on the mean intraocular pressure (IOP) or the proportion of patients who reach a specific IOP level, should the estimate of the IOP or IOP-reduction be based on single eyes, mean of bilaterally eligible and identically treated eyes or the difference between an eye with active treatment and a placebo treated contralateral eye, and is mean of replicated recordings useful? Statistical methodological conclusions: the most effective response variable varies with the selected patient population. Therefore, the trial design process should include a comparison of the variability, test power and required sample size for the possible response variables in a sample of the target population. At minimum a statistical consideration should be done.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 54 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 0282-7476 ; 1235
Ophtalmology, mean intraocular pressure, target intraocular pressure, latanoprost, timolol, open-angle glaucoma, ocular hypertension, trial design, Oftalmiatrik
National Category
Research subject
urn:nbn:se:uu:diva-3392 (URN)91-554-5570-0 (ISBN)
Public defence
2003-05-03, Grönwallsalen, Uppsala University Hospital, entrance 70, Uppsala, 13:15
Available from: 2003-04-07 Created: 2003-04-07Bibliographically approved

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