Purpose
The contribution of episcleral venous pressure (EVP) to the elevation of intraocular pressure (IOP) in open angle glaucoma (OAG) is unknown. Previous studies of EVP in OAG have been contradictory. In this study, we used a new automated venomanometer to investigate differences in EVP between untreated OAG patients and normal individuals. We also evaluated relationships between EVP and other ocular and systemic variables in OAG patients.
Methods
EVP was measured by using a computer-controlled venomanometer (pressure-chamber method) in one eye each of 101 subjects with untreated OAG (mean age, 64 years; range 24 to 83 years) and 191 eyes of 100 healthy volunteers (mean age, 48 years; range 19 to 81 years). We also measured intraocular pressure (IOP), axial length (AL), central corneal thickness (CCT), systolic and diastolic blood pressure (SBP and DBP respectively), height and weight, and calculated body mass index (BMI). Descriptive statistics were calculated for IOP and EVP, and differences between groups were examined by using generalized estimating equation (GEE) models. Relationships between EVP and IOP, SBP, DBP, BMI, AL, and CCT in glaucomatous subjects were assessed by using Pearson correlation and significance was determined by using GEE models.
Results
IOP of normal eyes and eyes with OAG was 13.7 ± 3.0 mmHg (mean ± SD) and 27.4 ± 8.0 mmHg respectively (p<0.001). EVP of normal eyes and eyes with OAG was 6.9 ±1.9 mmHg and 7.7 ± 2.0 mmHg respectively (p=0.003). In OAG patients, there were no significant correlations between EVP and any of the physiologic variables assessed (Table 1).
Conclusions
EVP in OAG is elevated by a small amount compared with normal subjects, and although the increase could contribute in a small part to the elevation of IOP, it is not a primary cause of high IOP in these patients. EVP in OAG is not related to age, CCT, IOP, axial length, BMI, or blood pressure.
Keywords: 568 intraocular pressure •
633 outflow: trabecular meshwork