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D.S. Greenfield, J.M. Liebmann, R. Ritch, T. Krupin, Low–pressure Glaucoma Study Group; Visual Field Asymmetry Is Unrelated to Intraocular Pressure Asymmetry in the Low–Pressure Glaucoma Treatment Study . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3577.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To evaluate the association of baseline IOP and visual field (VF) parameters in the Low–pressure Glaucoma Treatment Study (LoGTS). Methods: LoGTS is a randomized, double–masked trial to evaluate VF stability in patients randomized to topical twice–daily brimonidine tartrate 0.2% versus twice daily timolol maleate 0.5%. LPG was defined as open angle glaucoma with a glaucomatous VF defect in at least one eye on Humphrey 24–2 full–threshold standard automatic perimetry and all known IOP < 22 mmHg. Baseline measurements included untreated diurnal IOP curve (8 am, 10 am, 12 pm, and 4 pm), central corneal thickness (CCT) measurements, and stereophotography. A baseline VF was created using the average of two Humphrey 24–2 full–threshold exams. Results:190 patients were enrolled (mean age 64.9 ± 10.7 yrs) with an average VF mean deviation (MD) of –5.7 ± 4.1 dB. VF MD and PSD were not correlated with CCT or mean, peak, trough, or peak – trough (P–T) IOP (p=0.2–0.9, ANOVA). CCT was significantly associated with mean, peak, and trough IOP (p=0.002–0.008). Among patients with unilateral VF loss (N=53, 27.9%), there were no differences (p=0.3 –0.9, paired t–test) in any IOP parameter between fellow normal and glaucomatous eyes: mean diurnal IOP (15.7 ± 2.3, 16.0 ± 2.5) peak IOP (17.1 ± 2.6, 17.4 ± 2.6) trough IOP (14.1 ± 2.4, 14.5 ± 2.7) and P–T IOP (3.0 ± 1.5, 2.8 ± 1.5). Among patients with bilateral VF loss (N=137, 72.1%), mean, peak, trough, and P–T IOP were similar in eyes with better VF MD compared to eyes with worse VF MD (p=0.2–0.7, paired t–test). Cross–classified 3 X 3 contingency tables demonstrated no relationship between IOP and VF MD using chi–square analysis in all patients (p = 0.13), bilateral patients (p = 0.61), or unilateral patients (p = 0.11) and Goodman–Kruskal's index of association in all patients (0.06), bilateral patients (0.01), and unilateral patients (0.07).Conclusions:Contrary to previous reports, baseline VF asymmetry is unrelated to untreated IOP asymmetry in LPG.
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