Background: Various authors report that the glaucomatous loss of function is due to a chronic anterior ischemic optic neuropathy, being caused by a disturbed relationship between intraocular pressure and perfusion pressure in the posterior short ciliary arteries, which possibly leads to increased resistance in the ciliary vascular system. The authors attempt to test this hypothesis by measuring the vascular resistance (Resistance Index) in the ciliary vessel system by means of color Doppler sonography.
Patients and methods: 35 eyes of 35 patients, suffering from open angle glaucoma (OAG), with a mean age of 65.3 years, were examined as well as 35 eyes of 35 patients with normal tension glaucoma (NTG), whose mean age was 65.8 years. Both glaucoma groups were compared to an age- and sex-matched control group of healthy volunteers. The color-Doppler measurements were performed with an Acuson 128 XP/10, which allows imaging of all retrobulbar arteries, the ophthalmic artery, the central retinal artery and the short posterior ciliary arteries, and also guarantees the precise calculation of blood flow velocity and resistive index (RI). The RI was statistically evaluated.
Results: The resistance index of all retrobulbar arteries showed a statistically significant increase (p < 0.05) according to Wilcoxon's test in the OAG group as well as the NTG group.
Conclusions: Increased vascular resistance was found in all retrobulbar arteries in OAG and in NTG. These findings point out the pathognomonic importance of perfusion disturbance in glaucoma.