Timolol increased retrobulbar flow velocities in untreated glaucoma eyes but not in ocular hypertension

Purpose: To investigate retrobulbar blood flow velocities and the effects o f topical timolol treatment in eyes with newly detected, previously untreat ed open angle glaucoma or ocular hypertension. Methods: Fifteen eyes with open angle glaucoma (OAG) and 12 eyes with ocula r hypertension (OH), in the same number of patients, all untreated and newl y detected, were examined with colour Doppler imaging of retrobulbar vessel s before and after I month of topical timolol treatment (0.5% Timoptic (R) BID). Results: Baseline central retinal artery end diastolic velocity was lower ( 48%, p=0.0002) and resistive index higher (7.6%, p=0.018) in the OAG group than in the OH group. In the glaucoma group mean end diastolic velocity inc reased by 41%, (p=0.006) while resistive index decreased by 5.8%, (p=0.02) on treatment, while no significant changes were seen in the OH group. Blood flow velocities in the ophthalmic artery did not change with treatment. Ba seline IOP and IOP reduction did not differ between OAG and OH group. Conclusion: Peripheral resistance to blood flow was found to be increased i n untreated glaucoma eyes as compared to a similar group of eyes with ocula r hypertension. Timolol treatment diminished resistance significantly in th e glaucoma group, but not in the ocular hypertension group. Thus the two gr oups responded differently to timolol treatment. The reaction to IOP loweri ng treatment could indicate defective autoregulation in the glaucoma group.