Episcleral Venous Pressure in Untreated Primary Open-Angle and Normal-Tension Glaucoma

The aim of this prospective study was to investigate episcleral venous pressure (EVP) in different forms of glaucoma in comparison with age-matched controls. EVP was measured by means of a venomanometer in 32 eyes with untreated primary open-angle glaucoma (POAG), 36 eyes with untreated normal-tension glaucoma (NTG) as well as 56 control eyes without ophthalmological disease other than cataract. In addition to ophthalmological standard examination, cardiovascular parameters such as systolic and diastolic blood pressure and heart rate were recorded. In the POAG group, EVP was 12.1 ±0.5 mm Hg and in the NTG group 11.6 ± 0.4 mm Hg. This was significantly different from EVP of the controls (9.5 ± 0.2 mm Hg). The EVP/intraocular pressure (IOP) ratio was significantly different in NTG patients (80.0% ± 3.2) in comparison with both POAG patients (67.1% ± 2.8) and controls (69.2% ± 2.4). The difference between IOP and EVP (IOP – EVP) was 6.2 ± 0.6 in the POAG, 3.1 ± 0.45 in the NTG and 4.5 ± 0.4 in the control group. All these values were significantly different from each other. Regression analysis revealed a significant linear correlation between EVP and IOP in both the NTG and the POAG group. In the control group, however, the correlation was weak. This study is the first to demonstrate differences in EVP between untreated NTG and POAG and an age-matched healthy control group.