Document Detail

Repeatability of measurements of effectiveness of glaucoma medication.
MedLine Citation:
PMID:  22989663     Owner:  NLM     Status:  Publisher    
AIMS: To determine short-term repeatability of the effect of intraocular pressure (IOP) reducing medication and the number of repeated measurements necessary to estimate therapeutic effect with a given degree of precision. METHODS: IOP was measured at 8:00, 11:00 and 16:00 h at each of three weekly visits in untreated patients with primary open-angle glaucoma or ocular hypertension. After starting travaprost (0.004%) to both eyes, the measurements were repeated for a further three weekly visits. Repeatability of the change in IOP 1, 2 and 3 weeks after starting treatment was reported as the coefficient of repeatability (CR) and coefficient of variability (CV). RESULTS: Mean reduction in IOP was 7.5 mm Hg (29.9%). CR and CV between visits were 7.8 mm Hg and 37.2%, respectively. Repeated estimates of the effectiveness of treatment in the same subject at the same time of day would, therefore, be expected to lie within a range of 7.8 mm Hg and within ±73.2% of the mean effect with 95% confidence. A reduction in IOP less than 7.8 mm Hg over a single pair of measurements would be indistinguishable from measurement error. Precision improves from ±73.2% for a single pair of readings to ±25.9% for eight pairs. CONCLUSIONS: Day-to-day repeatability in the estimation of medication effectiveness is poor even for time-of-day standardised measurements and the number of IOP measurements required to achieve precision adequate for use in clinical practice is large.
Alan P Rotchford; Anthony J King
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-18
Journal Detail:
Title:  The British journal of ophthalmology     Volume:  -     ISSN:  1468-2079     ISO Abbreviation:  Br J Ophthalmol     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0421041     Medline TA:  Br J Ophthalmol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Tennent Institute of Ophthalmology, Gartnavel Hospital, Glasgow, UK.
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