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S. R. Rai, J. H. K. Liu, F. A. Medeiros, R. N. Weinreb; Right versus Left Asymmetry of 24 Hour Intraocular Pressure Response to Medical Treatment. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4821.
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To assess the asymmetry in right versus left intraocular pressure (IOP) responses to monocular therapy of travoprost or timolol over a 24-hour period.
Thirty-four patients (ages 41-78 years) with untreated open-angle glaucoma or ocular hypertension were included. Patients were housed in a sleep laboratory for 24 hours and baseline IOP profiles were created. Measurements of IOP were taken in both eyes using a pneumatonometer every two hours in the sitting position during the diurnal period (7 AM to 11 PM) and in the supine position during the nocturnal period (11 PM to 7 AM). Seventeen patients then initiated the treatment with 0.004% travoprost in both eyes once before bedtime (Group I) and seventeen patients with the 0.5% timolol treatment in both eyes once in the morning (Group II). Upon completion of at least four weeks of treatment, patients were housed in the sleep laboratory again for collecting the second 24-hour IOP data. The mean baseline IOPs and mean IOP changes in response to the monotherapy were calculated for the right and left eyes during the office-hour (9 AM to 5 PM), diurnal, nocturnal, and 24-hour periods. The strengths of association between right and left eye IOP prior to initiation of therapy and IOP responses to the treatment were evaluated using the coefficient of determination (R2).
For the group I prior to treatment, coefficients of determination between baseline IOPs in the two eyes were 0.413, 0.349, 0.438, and 0.360 during the office-hour, diurnal, nocturnal, and 24-hour periods, respectively. Under the travoprost treatment, coefficients of determination between IOP reductions in the two eyes were 0.173, 0.048, 0.413, and 0.197 during the office-hour, diurnal, nocturnal, and 24-hour periods. For the group II, pre-treatment coefficients of determination between baseline IOPs in the two eyes during the office-hour, diurnal, nocturnal, and 24-hour periods were 0.425, 0.453, 0.597, and 0.442, respectively. Under the timolol treatment, the corresponding coefficients of determination between IOP reductions in the two eyes were 0.372, 0.269, 0.727, and 0.423.
The strengths of association between the right and left IOP responses to the travoprost or timolol treatment were weak to moderate. This suggests that the monocular therapeutic trial may not necessarily predict the response of the fellow eye to topical therapy. The strengths of association for the IOP responses to the timolol treatment were better than those for the IOP responses to the travoprost treatment, which may reflect the fact that there was a crossover effect on IOP under the timolol treatment.
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