To investigate localization in glaucomatous visual field defects that are vulnerable to posture-induced intraocular pressure (IOP) changes.

Prospective cross-sectional study.

Ninety-three eyes of 93 newly diagnosed cases with normal tension glaucoma were examined. The IOP was measured in both the sitting and lateral decubitus positions with an Icare rebound tonometer. Visual field tests were performed with a Humphrey Field Analyzer with the Central 30-2 program using Swedish Interactive Threshold Algorithm standard strategies. The total deviation (TD) map values of 51 tested points were used for the analysis. A regression analysis was conducted to investigate relationships between TD in each point or cluster and posture-induced IOP changes. A linear mixed-effects model was used to identify factors associated with TD changes in each visual field cluster. Main outcome measures included the relationship between posture-induced IOP changes and localization of visual field defects.

There were 54 women and 39 men (mean age, 53.4 ± 12.5 years). The mean IOP per Icare rebound tonometer was 15.5 ± 3.2 mm Hg in the sitting position and 18.8 ± 3.1 mm Hg in the lateral decubitus position. The postural IOP difference was 3.3 ± 1.8 mm Hg (P < .001; range, −1.0 to 7.7 mm Hg). There was a significant negative correlation between TD and posture-induced IOP changes in 4 contiguous central points located just above the horizontal meridian. A linear mixed-effects model revealed a significant association between the difference in postural IOP change and decreased TD in the superior paracentral visual field according to multivariate analysis (P = .010).

Posture-induced IOP variations have been shown to be associated with glaucomatous superior paracentral visual field defects.