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D. C. Musch, B. W. Gillespie, P. R. Lichter, L. M. Niziol; Intraocular Pressure Control as a Contributing Factor to Long-Term Visual Field Loss in the Collaborative Initial Glaucoma Treatment Study. Invest. Ophthalmol. Vis. Sci. 2007;48(13):847.
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To evaluate the impact of various measures of intraocular pressure (IOP) control on progression of visual field (VF) loss during long-term treatment for newly diagnosed, open-angle glaucoma (OAG).
607 patients with newly-diagnosed OAG were randomly assigned to initial treatment with medications or with trabeculectomy. These patients underwent examination at six-month intervals by standardized testing, including Goldmann applanation tonometry and Humphrey 24-2 full threshold VF tests. Repeated measures analyses were conducted using SAS Proc Mixed and Genmod to develop predictive models for VF outcomes based on the mean deviation (MD) from VF testing. Analyses included follow-up data extending through nine years post-randomization. Statistical modeling of VF loss over time adjusted for age, sex, race, baseline VF loss, treatment, and time. IOP was included as a time dependent variable, and its association with VF loss was assessed in the period from 3 to 9 years post-randomization.
Measures of IOP control included the maximum IOP, mean IOP, standard deviation of IOP, proportion of IOP measurements under 16, 18, 20, or 22 mmHg, and whether all IOP values were under the these four cut-points. Two measures of IOP control - the maximum IOP value and standard deviation of IOP - were significantly associated both with the mean VF (p<0.0001) and the frequency of substantial VF loss in the 3 to 9 year period (p≤0.002). For example, a 1 mmHg increase in the maximum IOP is associated with a 7% increase in the predicted odds of a 3 or more decibel worsening of the mean deviation from VF testing. Likewise, a 1 mmHg increase in the standard deviation of IOP is associated with a 24% increase in the predicted odds of a 3 or more decibel worsening of the mean deviation.
Occurrences of high IOP and evidence of more variation in IOP measures are strongly predictive of progressive VF loss over an extended period of treatment. These results support regular monitoring of IOP in patients under treatment, and considering more aggressive treatment when undue elevation or variation in IOP measures are observed. Review of the patient’s IOP record over an extended time is an important component of evaluating a patient’s glaucoma treatment.
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