Abstract
Purpose: :
Reduced ocular perfusion pressure is a risk factor for the prevalence, incidence and progression of glaucoma. Recently, it was reported that diurnal fluctuations of ocular perfusion pressure constitute an independent risk factor for glaucoma. In the present study we investigated whether patients with primary open angle glaucoma also show increased diurnal fluctuations in ocular blood flow parameters.
Methods: :
In the present study 16 patients with POAG and 16 healthy age-matched controls were included. Ocular and systemic blood flow parameters and intraocular pressure were measured 4 times between 8 a.m. and 8 p.m. Optic nerve head blood flow and choroidal blood flow were measured with a fundus camera based laser Doppler flowmeter. In addition ocular fundus pulsation amplitude was assessed with laser interferometry. Coefficients of variation of these measurements were calculated for each patient. Diurnal fluctuation was quantified using the means of these individual coefficients of variation. In addition, linear regression analysis was performed to investigate whether the changes from early morning measurements were correlated.
Results: :
Optic nerve head blood flow, choroidal blood flow and fundus pulsation amplitude showed higher diurnal fluctuation in patients with POAG than in healthy controls (p < 0.05 each). By contrast, the diurnal variation in ocular perfusion pressure and intraocular pressure was comparable between the two groups. Changes of optic nerve head blood flow and choroidal blood flow on the one hand and optic nerve head blood flow and fundus pulsation amplitude on the other hand were correlated in patients with POAG, but not in healthy controls (p < 0.05 each). These changes in ocular hemodynamic parameters were, however, not associated with changes in ocular perfusion pressure or intraocular pressure.
Conclusions: :
The present study indicates that patients with PAOG have an abnormal diurnal fluctuation in ocular blood flow parameters. These fluctuations do not appear to be related to diurnal variations in ocular perfusion pressure. This result is compatible with the idea that POAG is characterized by unstable ocular blood flow and low grade ischemia reperfusion phenomena.
Keywords: ischemia • circadian rhythms • optic flow