Association between Serum Potassium with Risk of Onset and Visual Field Progression in Patients with Primary Angle Close Glaucoma: A Cross-Sectional and Prospective Cohort Study

Abstract

Evidence suggests that ion metabolism may be associated with oxidative stress in the ocular tissue in glaucoma patients. This study is aimed at determining whether serum ion levels are associated with the onset and/or visual field (VF) progression of PACG. A total of 265 PACG and 166 healthy subjects were included in the cross-sectional study. Meanwhile, 265 subjects with PACG were followed up every six months for at least two years in the cohort study. All subjects were evaluated for serum concentrations of ions (calcium, phosphorus, potassium (K+), sodium, and chlorine) and underwent VF examination. Logistic regression analysis was performed to assess the risk factors for PACG. Cox regression analyses and Kaplan-Meier survival analyses were performed to identify factors associated with VF progression in PACG subjects. In the cross-sectional study, the K+ level ( $4.31\pm 0.39\text{mmol}/\text{L}$ ) was significantly higher in the PACG group than in the normal group ( $4.16\pm 0.35\text{mmol}/\text{L}$ , $P<0.001$ ). Multiple logistic regression showed that the increased K+ level was a risk factor of PACG ( $\text{OR}=2.94$ , $95\%\text{CI}=1.63–5.32$ , $P<0.001$ ). In the cohort study, there were 105 PACG subjects with progression and 160 PACG subjects without progression. The progression group had significantly higher baseline serum K+ levels ( $4.41\pm 0.37\text{mmol}/\text{L}$ ) than the no progression group ( $4.25\pm 0.39\text{mmol}/\text{L}$ ) ( $P=0.002$ ). The increased level of K+ at baseline was associated with faster VF progression ( $\text{HR}=2.07$ , $95\%\text{CI}=1.23–3.46$ , $P=0.006$ ). PACG subjects with higher baseline K+ levels had significantly lower VF nonprogression rates (51.94%) than subjects with lower K+ levels (68.38%, log-rank test $P=0.01$ ). This study found that increased serum K+ level is a risk factor of PACG and is associated with faster VF progression in PACG, which might result from its influence on the oxidative stress process.