The response of retrobulbar vasculature to hypercapnia in primary open-angle glaucoma and ocular hypertension.

PURPOSE

To evaluate the physiological effects of hypercapnia on the retrobulbar vasculature in ocular hypertension (OH) and open-angle glaucoma (OAG).

METHODS

Peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistive index (RI) of the ophthalmic (OA) and central retinal arteries (CRA) were evaluated in 12 eyes with OH and 8 eyes with OAG using color Doppler imaging. Measurements were taken before and during hypercapnia.

RESULTS

Patients with OAG were found to have increased EDV (p < 0.035) of the CRA, and decreased PSV (p < 0.097) and EDV (p < 0.098) of the OA, during hypercapnia. Patients with OH had increased PSV (p < 0.062) and EDV (p < 0.072) of the CRA during hypercapnia. Patients with OH also demonstrated a greater percent change in the calculated RI (p < 0.065) of the CRA in response to hypercapnia when compared to OAG. The mean RI of the CRA decreased during hypercapnia.

DISCUSSION

Patients with OH were found to have a normal vasodilatory response within the retrobulbar vasculature during hypercapnia resulting in increased volumetric blood flow to the retina while patients with OAG did not, suggesting there is vasospasm at or downstream from the CRA resulting in decreased volumetric blood flow to the retina.