Purpose To analyze dynamics of retinal vessel dilation response to flicker light in patients with glaucoma and ocular hypertension. Patients and methods Response to flicker light was measured in retinal vessels by means of Retinal Vessel Analyzer. After the baseline 50 seconds long diameter recording of inferior and superior temporal artery and vein, three flicker stimulations of 20 seconds duration was applied, with a 80 seconds break in between. Area under the curve of the vessel diameter (AUC) was compared during 3 flicker periods in the open angle glaucoma patients group (POAG, n=47) and ocular hypertensives (OHT, n=46) and age-matched healthy controls (n=56) Results POAG eyes demonstrated smaller response of all vessels to flicker light in general than the other two groups (p=0.0008), but the response dynamics was significantly different between the groups (p=0.038), showing in three flicker periods a delayed increasing response in the POAG and OHT groups, and remaining stable in healthy subjects. Conclusion General vessel response to flicker light was decreased in POAG patients despite the slow improvement in repeated flicker stimulation, indicating an altered response pattern.

The maximum dilatory amplitude was significantly lower in vessels in the vasospastic group. An augmentation of the maximum vasodilation was observed in the nonvasospastic group after repeated flicker stimulations, a phenomenon that was missing in arterioles of vasospastic subjects. It seems that such different behavior is due to the opposite baseline offsets in interflicker periods in the two groups.

ABSTRACT.Purpose: This study aimed to determine whether ocular pulse amplitude (OPA) measured with dynamic contour tonometry (DCT) is related to systemic blood pressure (BP) parameters. Methods: Blood pressure was measured continuously and simultaneously with OPA in one randomly selected eye in 29 healthy subjects. Systemic parameters of interest were: systolic and diastolic BPs and their difference (BP amplitude), and left ventricle ejection time (LVET; defined as the time between the diastolic trough and the incisural notch in the BP curve). In addition, the axial length (AL) of the eye was measured. Associations between OPA, AL and systemic cardiovascular parameters were analysed in a multivariate regression model. Results: Measurements of OPA ranged from 1.0 mmHg to 4.9 mmHg (mean 2.3 ± 0.9 mmHg, median 1.9 mmHg). In a univariate analysis with one predictor at a time, means of intraocular pressure (IOP) (p = 0.008), AL (p = 0.046) and LVET (p = 0.037) were significantly correlated with OPA, whereas systolic and diastolic BPs and their amplitude were not. A multiple linear regression analysis showed that mean IOP (p < 0.005), AL (p = 0.01) and LVET (p = 0.002) all independently contributed to OPA. Conclusions: The OPA readings measured with DCT in healthy subjects were not related to BP levels and amplitude. It seems that the OPA strongly depends on the time)course of the cardiac contraction. Regulating mechanisms in the carotid system as well as scleral rigidity may be responsible for dampening the direct effect of BP variations.

General vessel response to flicker light was decreased in POAG patients, compared to normal controls and OHT patients. In contrast to significant correlation between the two contralateral eyes of the flicker response itself, only its borderline correlation to IOP was seen. There was no correlation to the level of damage, altogether indicating a systemic dysregulation phenomenon. GRANTS: Swiss National Foundation Grant 3200B0-113685, Velux Stiftung Grant, Freie Akademische Gesellschaft (FAG) Grant, Pfizer Inc. Grant CLINICAL TRIAL REGISTRATION REFERENCE NUMBER: ClinicalTrials.gov NCT00430209.

Baseline ChBF was lower in both the POAG and the OHT patients, compared with that in the controls. The stronger increase in ChBF in POAG patients in the face of an exercise-induced blood pressure increase indicates less active regulatory capacity in glaucoma patients.