Objective: To explore the relationship between asymmetric baseline intraocular pressure (IOP) and asymmetric visual field (VF) loss in the Low-Pressure Glaucoma Treatment Study.

Methods: Randomized, multicenter, controlled clinical trial. Methods: Low-pressure glaucoma (LPG) patients 30 years or older were identified. Exclusion criteria included an untreated pressure > 21 mmHg, advanced VF loss, and contraindications to study medications. Methods: A baseline VF was created using the average of 2 reliable Humphrey full-threshold examinations. A baseline diurnal IOP curve was performed without IOP-lowering medication. Methods: Mean diurnal, peak, trough, IOP range (peak - trough), and standard deviation (SD) of IOP measurements, and mean deviation (MD) and corrected pattern SD (CPSD) of VF examinations.

Results: One hundred ninety patients were enrolled (mean age, 64.9+/-10.7 years). Mean deviation and CPSD were not correlated with mean, peak, trough, or peak minus trough (P - T) IOP (Ps = 0.2-0.9). Among patients with unilateral VF loss (n = 53 [27.9%]), there were no differences (Ps = 0.3-0.9) in any IOP parameter between the normal VF eye and fellow glaucomatous eyes. Among patients with bilateral VF loss (n = 137 [72.1%]), mean, peak, trough, and P - T IOPs were similar in eyes with a better VF MD compared with eyes with a worse VF MD (Ps = 0.2-0.7). Cross-classified contingency tables demonstrated no relationship (Ps = 0.1-0.3) between IOP and VF MD or CPSD using chi-square analysis.

Conclusions: Intraocular pressure asymmetry is unrelated to VF asymmetry in the Low-Pressure Glaucoma Treatment Study, suggesting an unclear pathogenic relationship between IOP and glaucomatous damage in eyes with LPG.