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Open Access Highly Accessed Research article

Long-term effect of latanoprost/timolol fixed combination in patients with glaucoma or ocular hypertension: A prospective, observational, noninterventional study

Oliver Schwenn*, Barbara Heckmann, Claudia Guzy and Paul J Miller

BMC Ophthalmology 2010, 10:21  doi:10.1186/1471-2415-10-21

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Treatment with latanoprost/timolol fixed combination

A. Wegner   (2010-11-03 07:21)  Glaucoma Service, Department of Ophthalmology, Klinikum rechts der Isar, Technische Universitaet Muenchen, Munich, Germany

I have with great interest read the article of Schwenn et al [1].
The Study has various flaws, in the design of the study as well as at the endpoints and analyses.
Intraocular pressure (IOP) was measured with various methods that are not comparable [2].
The Goldmann measured IOP was corrected in relation to central corneal thickness (CCT). The measurement of CCT varies according to the method used (ultrasound, optical coherence tomography, Sheimpflug) [3]. The method of measuring CCT was not standerized. Therefore, even the group of patients with Goldmann measured IOP has to be divided into sub-groups according to the method CCT was measured.
There are no quantitative definitions of efficacy, only subjective and vague descriptive. I would presume that there is a broad spectrum of variability in the definition of efficiency or tolerance of treatment among 557 ophthalmologists.
There is no discrimination between patients with ocular hypertension and glaucoma.
Almost 30% of the patients had been switched to a fixed combination, even though that the IOP was well controlled. Those patients can not be evaluated together with patients with uncontrolled IOP.
One of criteria of progression is a subjective impression of the clinician - "progressive visual field deterioration noted by the physician". Such end points can not used in scientific study.
Visual field examination were not unified, neither which perimeter was used nor the strategy (fast or full threshold).
The only statement that can be made from this study is that latanoprost/timolol fixed combination is used to treat raised IOP.

1. Schwenn O, Heckmann B, Guzy C, Miller PJ: Long-term effect of latanoprost/timolol fixed combination in patients with glaucoma or ocular hypertension: a prospective, observational, noninterventional study. BMC Ophthalmol. 2010, 10:21.

2. Tonnu PA, Ho T, Sharma K, White E, Bunce C, Garway-Heath D. A comparison of four methods of tonometry: method agreement and interobserver variability. Br J Ophthalmol. 2005, 89:847-50.

3. Chen S, Huang J, Wen D, Chen W, Huang D, Wang Q. Measurement of central corneal thickness by high-resolution Scheimpflug imaging, Fourier-domain optical coherence tomography and ultrasound pachymetry. Acta Ophthalmol. no. doi:10.1111/j.1755-3768.2010.01947.x.

Competing interests

none
When you publish, please write my full name, Aharon Wegner.

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