Various intercellular messenger molecules, such as nitric oxide, adenosine and prostanoids, released by perivascular tissue have been implicated in the control of local blood flow. The present work performed in vitro on isolated retinal arteries advances that perivascular retinal tissue releases yet another intercellular messenger molecule exerting a potent vasodilatory ...

Disruption of the blood-aqueous barrier (BAB) induced by retinal photocoagulation and cryopexy in pigmented rabbits was evaluated by laser flare photometry. A significant increase in flare values after retinal photocoagulation was measured from the 1st postoperative day, with values returning to baseline levels by day 7. Cryopexy induced consistently high ...

BACKGROUND: To investigate retinal capillary blood flow characteristics in patients with age-related maculopathy (ARM). METHODS: Retinal capillary blood volume (VOL), blood flow (FLOW), and velocity (VEL) were measured in four macular sectors (I, II, III, IV) and in two areas beyond the temporal superior and inferior major vessel arcades (V ...

BACKGROUND: Investigation of retinal blood flow in patients with and without diabetic retinopathy (DR). Retinal blood flow is measured with the non-invasive Heidelberg Retinal Flowmeter (HRF). The clinical suitability of the HRF in patients with diabetes mellitus is investigated, and measured blood flow is compared with blood flow in a ...

Ifenprodil tartrate has long been employed as a cerebral vasodilator with alpha and N-methyl-D-aspartate (NMDA) receptor antagonistic activities. The purpose of this study was to evaluate the effects of ifenprodil on ocular circulation in rabbits. Experiments were performed during the dark phase in Dutch rabbits conditioned to a schedule of ...

PURPOSE: To study the blood flow velocity in the central retinal vein after the resolution of non-ischemic central retinal vein occlusion (CRVO) with optociliary vein (OCV). METHODS: Eleven patients and 22 healthy volunteers were studied. Indocyanine green (ICG) angiography was used to investigate the choroidal veins in the affected eyes. ...

PURPOSE: To characterize optic disk blood flow in patients with open-angle glaucoma compared with age-matched healthy control subjects. METHODS: In this prospective cross-sectional study, 90 eyes of 90 patients with open-angle glaucoma and 61 eyes of 61 age-matched healthy control subjects were evaluated. Flow in the optic disk cup and ...

The retina receives its nutrients from two separate circulations: retinal and choroidal circulation. This short overview describes the determinants in the regulation of these circulations. Retinal circulation is characterized by a low blood flow while flow in the choroid is high. The choroidal circulation is mainly controlled by sympathetic innervation ...

PURPOSE: To investigate the mechanisms of action of endothelin (ET)-3 on the regulation of retinal hemodynamics in diabetic and nondiabetic rats. METHODS: Retinal blood flow changes were measured using video fluorescein angiography. Measurements were made before and after intravitreal injections of different ET-3 concentrations in nondiabetic rats and rats with ...

Retrograde cerebral perfusion via the superior vena cava during deep hypothermic circulatory arrest has evolved as a means of cerebral protection in aortic-arch surgery. We showed, with use of fluorescein retinal angiography, that during retrograde cerebral perfusion, fluorescein injected into the superior vena cava entered the retinal venules, flowed to ...

PURPOSE: To demonstrate an indocyanine green (ICG) angiography-based clinical method for characterizing choroidal blood flow and for detecting changes in choroidal circulation patterns, and by use of that method, to demonstrate that pentoxifylline affects choroidal blood flow. METHODS: High-speed ICG angiography was performed in rhesus monkeys before and after intravenous ...

PURPOSE: (a) To show that high-altitude retinopathy (HAR) is common at high altitudes even in well-acclimatised climbers and that it should not be regarded as part of the spectrum of benign mountain sickness but rather as a clinical sign with a separate aetiology. (b) To test the hypothesis that HAR ...

A 23-year-old woman presented with abdominal pain and blurred vision in both eyes. Fundoscopy revealed large bullous detachments of her neurosensory retina with shifting subretinal fluids bilaterally. Laboratory studies showed a hemoglobin of 6.5 mmol/l, thrombocytes 20x10(9)/l, and LDH 1098 U/l. A peripheral blood smear revealed red blood cell fragmentation. ...

Noninvasive monitoring of blood flow in retinal microcirculation may elucidate the progression and treatment of ocular disorders, including diabetic retinopathy, age-related macular degeneration, and glaucoma. Color Doppler optical coherence tomography (CDOCT) is a technique that allows simultaneous micrometer-scale resolution cross-sectional imaging of tissue microstructure and blood flow in living tissues. ...

Purpose: Using a new analysis program for scanning laser-Doppler flowmetry (SLDF) by a Heidelberg retina flowmeter (HRF), we studied the relation between flow and visual field or disc morphology.Subjects and Methods: In 42 eyes of 21 patients with normal tension glaucoma (NTG) the mean-flow of the HRF blood flow parameters ...

The purpose of the present study was to determine the regional blood flow in the myopic chick eye during and after short-term monocular form deprivation. Chicks were monocularly form-deprived by covering one eye with a translucent occluder for 7-10 days. The anterior chamber-lens distance, the vitreous chamber length and the ...

Purpose: The effect of topical 2% carteolol hydrochloride on the ocular blood flow dynamics in normal human eyes was studied.Materials and Methods: Ten healthy volunteers were studied using color Doppler imaging and scanning laser Doppler flowmetry. In the first experiments, one eye received 30 µl of 2% carteolol hydrochloride twice ...

PURPOSE: This article assesses the hypothesis that the high blood flow rate and low O(2) extraction associated with the choroidal circulation are metabolically necessary and explores the implications of the spatial relationship between the choroid and the photoreceptors for metabolism in the normal and detached retina. METHODS: The O(2) distribution ...

PURPOSE: There is evidence from animal studies that nitric oxide (NO) is a major determinant of ocular blood flow. In humans NO synthase inhibition reduces pulsatile choroidal blood flow, but no data on optic nerve head (ONH) vasculature are available yet. The goal of this study was to investigate the ...

The choroid is the main source of oxygen to the retina. In contrast to the adult, the absence of autoregulation of choroidal blood flow in the newborn leads to hyperoxygenation of the retina. In the immature retina which contains relatively low levels of antioxidants this hyperoxygenation favors peroxidation including the ...

Electroretinogram (ERG) changes invariably accompany the selective interruption of the retinal circulation that occurs in human central retinal artery occlusion. Since arteriolar ligation or ocular hypertension in the rabbit eye is occasionally used to model human central retinal artery occlusion, we conducted the present study to determine whether selective interruption ...

Prostaglandin F(2alpha) analogues have recently been introduced on the market for glaucoma treatment. While these drugs have a well-documented intraocular pressure reducing effect only a limited number of studies have been published regarding their effects on the microvasculature in the eye. Since many naturally occurring prostaglandins have marked effects on ...

Patients with intrabulbar and intraorbital tumours have been investigated by colour Doppler imaging. In the first group there were 20 patients with malignant melanoma of the uvea and in the second group there were 19 patients with cavernous hemangioma. The third group was a control group represented by 20 healthy ...

The purpose of this study was to study the effects of ifenprodil, a cerebral vasodilator with alpha and N-methyl-D-aspartate (NMDA) receptor antagonistic activities, on aqueous humor dynamics and optic nerve head (ONH) circulation in rabbits. Experiments were performed during the dark phase in rabbits conditioned to a schedule of alternating ...

We report on what we believe is a novel approach to measuring the velocity of red blood cells (RBC's) at different depths of retinal vessels by use of low-coherence sources. The technique, variable coherence optical Doppler velocimetry (VCODV), performs Doppler shift measurements through autodyne mixing between the light scattered by ...

BACKGROUND: There is evidence that altered ocular blood flow is involved in the development and progression of diabetic retinopathy. However, the nature of these perfusion abnormalities is still a matter of controversy. Ocular haemodynamics were characterised with two recently introduced methods. METHODS: The cross sectional study was performed in 59 ...

PURPOSE: This study was performed to evaluate the transport kinetics of ascorbate in aqueous humor of conscious rabbits. METHODS: Following the development of a spectrophotometric assay for ascorbate in serum, aqueous humor and microdialysate, and preliminary studies of ascorbate systemic disposition in the rabbit, microdialysis probes were placed into the ...

Asymmetries in the optic flow on both eyes may indicate an unintended turn of an animal and evoke compensatory optomotor responses. On a straight path in an evenly structured environment, the optic flow on both eyes is balanced corresponding to a state of optomotor equilibrium. When one eye is occluded ...

PURPOSE: To evaluate the effects of topical latanoprost and timolol in combined therapy on retinal blood flow and tissue circulation in the optic nerve head (ONH) of the cynomolgus monkey. METHODS: Latanoprost (30 microL, 0.005%) was instilled once daily and timolol (30 microL, 0.5%) twice daily for 6 days into ...

PURPOSE: The purpose of this study is to confirm the reliability of scanning laser Doppler flowmetry in the rat retina and optic nervehead, and the validity of measuring changes of retinal blood flow in rats while breathing 100% oxygen. METHODS: We used a commercially available scanning laser Doppler flowmeter. To ...

This study was designed to determine the activity of bremazocine (BRE), a relatively selective kappa opioid receptor agonist, on intraocular pressure (IOP), aqueous humor formation and pupil diameter (PD) in conscious, normal, dark-adapted New Zealand white (NZW) rabbits. IOP was measured in normal and unilaterally sympathectomized rabbits using a calibrated ...

BACKGROUND: The pathogenesis of central retinal artery occlusions (CRAO) varies, depending upon the underlying disease. An embolic origin of an occlusion often occurs. PATIENT AND METHODS: A 50-year-old man with an occlusion of the left internal carotid artery was examined because of a left central retinal artery occlusion. Fluorescein angiography ...

PURPOSE: This study was planned to investigate blood flow changes due to scleral buckling surgery. In addition the effects on these changes of factors related to patient characteristics and operative technique were studied. METHODS: Central retinal artery (CRA) and ophthalmic artery (OA) blood flow velocities were studied with colour Doppler ...

We studied the time course of astrocyte invasion and blood vessel formation in the developing ferret retina using glial fibrillary acidic protein (GFAP)-immunohistochemistry for astrocytes and isolectin B4 histochemistry for blood vessels. As in other mammals, strongly GFAP positive astrocytes invade the ferret retina from the optic nerve. At birth, ...

Computerized image analysis, including fluorescein angiography, was used to evaluate the retinal, choroidal and optic disk blood flow in 16 patients with normal-tension glaucoma (NTG) and to correlate this measurement with visual fields, retinal vessel width, optic disk pallor and blood pressure (BP). The angle of the ascending slope of ...

PURPOSE: There is evidence that ocular blood flow strongly depends on arterial oxygen tension. Results from recent animal studies indicate that the vasoconstrictor response to hyperoxia may be mediated in part by an increased production of endothelin (ET)-1. In an effort to answer the question whether the retinal vasoconstrictive response ...

PURPOSE: Many physiological parameters, including blood pressure, show circadian variations. Diurnal fluctuations of the optic nerve head (ONH) circulation have not yet been studied. The purpose of the present study was to determine the pattern of ONH blood flow variations over a 24-hour period in healthy subjects. METHODS: The subject ...

Techniques for noninvasively measuring the oxygen saturation of blood in retinal arteries and veins are reported in the literature, but none have been sufficiently accurate and reliable for clinical use. Addressing the need for increased accuracy, we present a series of oximetric equations that explicitly consider the effects of backscattering ...

OBJECTIVE: To compare the efficacy of combinations of betaxolol-brinzolamide and timolol-dorzolamide as suppressors of aqueous humor flow and ocular hypotensive agents. DESIGN: Placebo-controlled, masked comparison of the two drug combinations. PARTICIPANTS: Twenty-five normal human volunteers with the fellow eye serving as control. METHODS OR TESTING: Fluorophotometric measurement of aqueous humor ...

PURPOSE: Several methods have been proposed for the investigation of the human choroidal circulation. The aim of the present study was to compare laser interferometric measurements of cardiac synchronous fundus pulsations with pneumotonometric measurements of intraocular pressure pulse and pulsatile ocular blood flow in humans. METHODS: The association between fundus ...

PURPOSE: We have shown in the companion paper that, under baseline conditions, there is a high degree of association between laser interferometrically measured fundus pulsation amplitude (FPA) and pneumotonometrically measured pulse amplitude (PA) and pulsatile ocular blood flow (POBF). The present study investigated the effect of high pCO2, of high ...

OBJECTIVE: To evaluate normal choroidal blood flow and its relationship with various factors such as age, systemic blood pressure, and intraocular pressure (IOP). METHODS: A total of 70 healthy subjects were recruited. Choroidal blood flow was assessed using a method based on laser Doppler flowmetry (LDF) technique. The LDF parameters ...

BACKGROUND: Insulin induces vasodilation in several tissues, including skeletal muscle and kidneys. OBJECTIVE: To investigate whether insulin may contribute to ocular blood flow regulation. METHODS: The study was performed in a balanced, randomized, placebo-controlled, single-masked, 3-way, crossover design in 9 healthy male subjects. Each subject received 2 doses of insulin ...

OBJECTIVES: Using a three-way crossover study design, we compared the effects of brinzolamide 2%, dorzolamide 2%, and placebo (vehicle) on microvascular optic nerve head (ONH) blood flow, intraocular pressure (IOP), blood pressure, heart rate, and acid-base balance in nine acepromazine-tranquilized Dutch-belted rabbits. METHODS: Baseline measurements were taken before treatment and ...

Diabetic retinopathy is progressive, and detection early is essential for the prevention of blindness. Doppler flowmetry, retinal photography, scanning laser ophthalmoscopy, and retinal oximetry measurements may identify proliferative disease early. Drawbacks of these methods include lack of compliance, failure to refer, and failure to identify disease early. As a result, ...

We evaluated the retrobulbar response to a selective versus nonselective beta blocker in a subgroup of primary open-angle glaucoma patients (POAG) characterized by ocular vasospasm. Eleven patients who exhibited ocular vasospasm (i.e. a significant increase in ophthalmic artery blood flow velocity or a significant decrease in ophthalmic artery resistance index ...

AIMS: To evaluate the effect of high dose stereotactic radiotherapy on the ocular blood flow of patients with uveal melanoma. METHODS: Colour Doppler imaging (CDI) was used to measure blood flow velocity and vascular resistance in the ophthalmic, short posterior, and central retinal arteries of nine patients suffering from uveal ...

BACKGROUND: A study was performed to evaluate the effect of isoxic hypercapnia on ocular haemodynamics using colour Doppler imaging (CDI), scanning laser Doppler flowmetry (SLDF) and ocular blood flow (OBF) tonography. METHODS: Measurements were taken for one eye of each of 14 healthy subjects (mean age 27 +/- 6 years) ...

PURPOSE: To investigate the effect of an intravenous infusion of carteolol on tissue blood flow in the optic nerve head (ONH) of rabbits. METHODS: Rabbits received either a 3-week topical instillation, or a single intravenous injection (10, 20, 30 microg/kg) or a continuous intravenous injection (2.5, 5, 20, 40, 80 ...

PURPOSE: To describe the pathophysiologic and the hemodynamic changes associated with branch retinal vein occlusion (BRVO) on the basis of selected angiographic observations from a cohort of patients with BRVO and related anomalies of retinal blood flow. DESIGN: Retrospective, observational case series. PARTICIPANTS: A total of 250 patients with incipient ...