Longitudinal Testing of Retinal Blood Flow in a Mouse Model of Hypertension by Laser Speckle Flowgraphy

Purpose

The purpose of this study was to investigate the applicability of laser speckle flowgraphy (LSFG) for a longitudinal study of blood flow parameters in mice before, during, and after continuous infusion of angiotensin-II.

Methods

Normotensive C57BL/6J mice were imaged by LSFG at one (n = 22) or three sessions (n = 10). Two additional cohorts were imaged by LSFG before, during, and after continuous infusion of angiotensin-II by minipump for 2 or 4 weeks (n = 6 and 8, respectively). Retinal blood flow, vascular resistance, and total area of retinal vascular flow, a surrogate of vascular remodeling and vasoconstriction, were determined at each time point.

Results

During infusion of angiotensin-II for 2 weeks, decreased retinal blood flow and area of vascular flow, as well as increased vascular resistance, were observed. These changes were reversed 1 week after the end of angiotensin-II infusion. In mice infused with angiotensin-II for 4 weeks, decreased retinal blood flow and increased vascular resistance persisted at 6 weeks postinfusion, despite a decrease in blood pressure.

Conclusions

Arterial hypertension, induced by continuous angiotensin-II infusion, results in reduced retinal blood flow, increased vascular resistance, and decrease in area of intravascular blood flow within retinal arterioles and venules. Sustained vasoconstriction 6 weeks after the end of a 4-week period of angiotensin-II infusion may indicate vascular remodeling after a period of chronic hypertension.

Translational Relevance

Retinal LSFG is useful for serial investigation of blood flow in mouse models and provides a novel approach for translational studies on the microvascular effects of hypertension in vivo.

Risk Score Predicting Primary Open-Angle Glaucoma Patients With Vascular Predisposition

Purpose

We tested the hypothesis that a questionnaire-based risk score predicts the prevalence of patients with primary open-angle glaucoma (POAG) with vascular predisposition.

Methods

The Flammer Syndrome Questionnaire (FSQ) was used to determine vascular risk scores in 823 healthy subjects and 512 patients with POAG. Next, we characterized blood flow pulsatility changes within the optic nerve head (ONH) in Flammer syndrome (FS) using laser speckle flowgraphy (LSFG) in 358 eyes of 206 patients with normal-tension glaucoma (NTG). Last, we examined the association between changes in Mean blur rate (MBRAve), an LSFG-derived ONH blood flow measurement, during cold provocation and the FSQ risk score in 56 eyes of 56 patients with NTG.

Results

Five FSQ-related symptoms were significantly associated in patients with POAG patients; cold hands/feet (odds ratio [OR] = 1.82), low blood pressure (BP; OR = 3.29), increased response to drugs (OR = 2.27), underweight (OR = 1.99), and tendency toward perfectionism (OR = 1.88). The vascular risk score showed the best discriminative accuracy in differentiating healthy subjects from patients with NTG (area under the curve [AUC] = 0.73). In the NTG eyes, ONH pulsatile blood flow in the FS group was characterized by greater pulsatility. Moreover, the negative correlation between the high FSQ risk score and the cold-induced ONH blood flow reduction was pronounced in eyes with NTG (correlation coefficient = -0.41).

Conclusions

The FSQ risk score can be a screening tool to identify patients with POAG with increased vascular stiffness and further reduced ONH blood flow during cold stress.

Translational Relevance

The vascular risk score may help tailor individual glaucoma care.