Prolonged retinal arteriovenous passage time is correlated to ocular perfusion pressure in normal tension glaucoma.

BACKGROUND: The pathogenesis of normal tension glaucoma (NTG) might be related to impaired autoregulation of ocular blood flow. The purpose of the study is to evaluate retinal haemodynamics by fluorescein angiography and to correlate arteriovenous passage times (AVP) with ocular perfusion pressure in patients with NTG and controls.

METHODS: Thirty-five patients with NTG without any topical treatment (mean age 53 +/- 11 years) and 35 age-matched controls (mean age 53 +/- 11 years) were included in this study. Retinal AVP was assessed by video fluorescein angiography using a scanning laser ophthalmoscope (Rodenstock, Germany). Dye dilution curves of temporal superior and inferior arterioles and venules were evaluated by digital image analysis. AVP was correlated to mean arterial blood pressure and ocular perfusion pressure.

RESULTS: The AVP was significantly prolonged in patients with NTG compared to controls (1.82 +/- 0.57 versus 1.42 +/- 0.46, p = 0.002). Patients with NTG and controls showed no significant differences in intraocular pressure, mean arterial pressure and mean and diastolic ocular perfusion pressure. The AVP was significantly correlated to mean arterial pressure and mean and diastolic ocular perfusion pressure in patients with NTG (r = -0.54; p = 0.0006, r = -0.51; p = 0.002, r = -0.49, p = 0.002), but not in controls (r = -0.21; p = 0.23, r = -0.19; p = 0.27, r = 0.02, p = 0.93).

CONCLUSIONS: Patients with NTG exhibit prolonged retinal AVP compared to controls. A significant correlation of retinal haemodynamics to mean arterial blood pressure and ocular perfusion pressure might reflect impaired autoregulation in NTG.