Lateral Posterior Ciliary Artery Research Articles

Microvasculature of the hamster eye: scanning electron microscopy of vascular corrosion casts

The architecture of the retina, choroid and anterior eye segment was investigated in 12 Syrian hamsters using scanning electron micrographs of methylmethacrylate corrosion casts. The hamster eye receives its primary blood supply from the long posterior ciliary artery, which directly enters the optic nerve head, and divides into three branches: the central retinal artery and medial and lateral long posterior ciliary arteries. In the retina the central retinal artery divides into six radiating branches. Retinal arterioles form a slender and long course to capillaries. Retinal capillaries are extremely thin in diameter and form a sparse capillary network. The choroid is supplied by the long posterior ciliary arteries. Choroidal arterioles exhibit a thick and short course to the choriocapillaris. The choriocapillaris is thick and sinusoid-like, forming a dense network in the choroid. The ciliary body, iris and bulbar conjunctiva are supplied by the anterior ciliary arteries, which are branches of the long posterior ciliary arteries. Capillaries supplying the anterior margin of the ciliary process are large in diameter with an irregular bore, forming a thoroughfare channel draining blood in the ciliary arterioles into the pars plana vessels. Blood from the retina is drained by the central retinal veins. Venules from the anterior eye segment empty into the vortex veins via the pars plana vessels. Venous blood from the choroid is drained only by vortex veins via the choroidal veins. The functional significance of the vascular architecture and species differences are discussed.

Doppler measurement of blood flow velocities in extraocular orbital vessels in patients with obstructive sleep apnea syndrome.

We used color Doppler sonography to determine blood flow velocities in the extraocular orbital vessels of patients with obstructive sleep apnea syndrome (OSAS) and compared the results with those of healthy control subjects without OSAS. Patients with OSAS were classified according to the apnea-hypopnea index (AHI) as having mild OSAS (AHI < 20) or severe OSAS (AHI > or = 20). The peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistance index were measured in the ophthalmic artery (OA), central retinal artery (CRA), lateral short posterior ciliary artery, and medial short posterior ciliary artery using color Doppler sonography. Only 1 eye was measured in each study participant, and right and left eyes were chosen randomly. The blood flow velocities of patients with OSAS and those of control subjects were compared with the Kruskal-Wallis test and Wilcoxon's rank-sum test. The study comprised 30 patients (15 with mild and 15 with severe OSAS) and 20 healthy control subjects. Blood flow velocities were higher in most measured vessels in patients with OSAS than they were in the control subjects. Among patients with mild OSAS, the PSVs and EDVs in the posterior ciliary arteries were statistically significantly higher than those of the control group (p < 0.05), but those in the OA and CRA did not differ significantly between the mild OSAS group and the control group (p > 0.05). However, as the severity of OSAS increased, the PSVs and EDVs of the OA and CRA were also affected (p < 0.05). Color Doppler sonographic measurements of blood flow parameters in the orbital vessels may differ significantly between patients with OSAS and those without the syndrome. Therefore, OSAS should be considered in addition to other conditions when interpreting the results of color Doppler sonography of the extraocular orbital vessels if the clinical history points toward such a diagnosis.

Extraocular Blood Flow and Endothelin-1 Plasma Levels in Patients with Multiple Sclerosis

In order to evaluate whether plasma levels of the potent vasoconstrictor endothelin-1 (ET-1) are increased in patients with multiple sclerosis (MS) and whether these patients exhibit an ET-1-mediated vascular dysregulation, ET-1 plasma levels were measured in 30 patients with MS. Blood flow velocities in the ophthalmic artery, central retinal artery, central retinal vein, short lateral posterior ciliary artery, and short medial posterior ciliary artery were assessed in parallel. ET-1 plasma levels were significantly increased in MS patients when compared to sex- and age-matched healthy controls (2.0 ± 0.4 pg/ml, range 1.1–2.8 vs. 1.5 ± 0.2 pg/ml, range 0.9–2.0; p < 0.001). Moreover, the patients exhibited significant alterations of extraocular blood flow. The role of ET-1 in the inflammatory process remains to be clarified.

Relationship between Blood Flow Velocities in Retrobulbar Vessels and Laser Doppler Flowmetry at the Optic Disk in Glaucoma Patients

The relationship between blood flow velocities in retrobulbar vessels and blood flow at the optic nerve in glaucoma patients was assessed in a prospective study. The Heidelberg retina flowmeter (HRF) was used to assess optic nerve head blood flow in 13 open-angle glaucoma patients. In the same patients, color Doppler imaging (CDI) measurements were obtained from the ophthalmic artery, the central retinal artery and the posterior ciliary arteries. Using data for one randomly selected eye per subject, correlations between HRF recordings and CDI measurements were evaluated by means of Spearman’s rank correlation factor. All three HRF parameters correlated with CDI measurements obtained from retrobulbar vessels. The most marked correlations were those of the HRF parameter ‘volume’ with the end-diastolic velocity in the ophthalmic artery and the medial posterior ciliary artery (R = 0.79, p = 0.0012 and R = 0.81, p = 0.0007, respectively), and the peak systolic velocity in the lateral posterior ciliary artery (R = 0.82, p = 0.0006). The present study suggests that glaucoma patients with altered blood flow in retrobulbar vessels are likely to show an alteration in optic nerve blood flow as measured with the HRF.

Evaluation of ocular arterial changes in glaucoma with color Doppler ultrasonography.

The purpose of this study was to evaluate hemodynamic changes of the retrobulbar vasculature caused by different intraocular pressures with color Doppler ultrasonography. Fifty normal eyes in 25 patients, 13 patients with normal tension glaucoma, and 19 patients with acute glaucoma and increased intraocular pressure (greater than 30 mm Hg) were enrolled in this study. In 15 of 19 patients with acute glaucoma patients, follow-up color Doppler ultrasonography was also undertaken after laser peripheral iridectomy when the intraocular pressure had returned to normal. The peak systolic velocity, end diastolic velocity, resistive index, time average maximum velocity, and pulsatility index were compared in different vessels, including the central retinal artery, lateral posterior ciliary artery, medial posterior ciliary artery, and ophthalmic artery in each orbit. The peak systolic velocity, end diastolic velocity, and time average maximum velocity of the central retinal artery were significantly lower (P<0.01) in acute glaucoma patients than in the control group. The resistive index and pulsatility index of the central retinal artery were significantly higher (P<0.01) in acute glaucoma patients than in the control group. The end diastolic velocity of the lateral and medial posterior ciliary arteries was significantly lower in patients with acute glaucoma than in the control group, and the resistive index and pulsatility index of both of these arteries were significantly higher (P<0.001) in patients with acute glaucoma than in the control group. However, no statistical significantly differences were found in the peak systolic velocity or time average maximum velocity in either of the posterior ciliary arteries; similarly, no statistically significant differences were noted in any of the parameters in the ophthalmic artery between the control group and the group with acute glaucoma. The pulsatility index of the central retinal artery and of the lateral and medial posterior ciliary arteries was significantly lower (P<0.01) in acute glaucoma patients after laser therapy than in acute glaucoma patients before laser therapy. The resistive index of both posterior ciliary arteries was also significantly lower (P<0.004) in acute glaucoma patients after laser therapy than before laser therapy. All parameters for all vessels examined among the normal subjects, the patients with normal tension glaucoma, and the patients with acute glaucoma after laser therapy when the intraocular pressure had returned to normal showed no statistically significant differences. Color Doppler ultrasonography is a good modality for both imaging and studying the hemodynamics of the perioptic nerve vessels.

Zinn–Haller arterial ring observed by ICG angiography in high myopia

AIMSTo delineate the entire Zinn–Haller arterial ring angiographically in vivo.METHODS382 highly myopic eyes (210 patients) with refractive errors greater than −8.25 D were examined using indocyanine green (ICG) videoangiography. A...

Blood-flow Velocities of the Extraocular Vessels in Patients With High-tension and Normal-tension Primary Open-angle Glaucoma

To evaluate blood-flow parameters in three different groups of patients with primary open-angle glaucoma. Hemodynamic parameters in the ophthalmic artery, central retinal artery, central retinal vein, and lateral and medial short posterior ciliary arteries were evaluated by color Doppler imaging in 237 patients with primary open-angle glaucoma and 124 age-matched normal control subjects. Group A consisted of 56 patients with primary open-angle glaucoma with treated intraocular pressure higher than 20 mm Hg; group B, of 103 patients with primary open-angle glaucoma with progression of glaucomatous damage despite intraocular pressure of 21 mm Hg or less; and group C, of 78 patients with normal-tension glaucoma. All patients showed a significant decrease in end-diastolic velocities (P < .01) and a significant increase in resistivity index (P < .05) in all arteries measured. Peak-systolic velocities were normal in the ophthalmic artery in all three groups. In the central retinal artery and the short posterior ciliary arteries, however, patients in groups B and C had significantly reduced peak-systolic velocity (P < .05) compared with normal control subjects. Peak-systolic velocity in group A did not differ significantly from that of normal control subjects. Maximal and minimal blood-flow velocities in the central retinal vein were significantly lower in groups B and C (P < .001) compared with normal control subjects. In group A, only minimal blood-flow velocity was significantly reduced (P < .05). Hemodynamic parameters in the extraocular vessels are altered in patients with glaucoma. Reduced blood-flow velocities may be secondary as well as contributory to glaucomatous damage.

Serotonin-induced constriction of ocular arteries in atherosclerotic monkeys. Implications for ischemic disorders of the retina and optic nerve head.

Ischemic disorders of the retina and optic nerve head, which constitute a common cause of visual loss, are usually seen in patients with atherosclerosis. To test the hypothesis that serotonin, which is released when platelets aggregate, may produce vasospasm in atherosclerotic monkeys and, thus, may contribute to the ischemic disorders and that short-term dietary treatment of atherosclerosis causes the propensity to vasospasm to subside. We studied the response of retinal and posterior ciliary circulation to serotonin in 18 atherosclerotic (25 eyes) and 5 normal (8 eyes) cynomolgus monkeys. The eyes were evaluated by color fundus photography and fluorescein fundus angiography. The eyes were examined under basal conditions and, at a different time, during the intravenous infusion of serotonin. In 6 of the 18 atherosclerotic animals, the evaluation was repeated 5 to 12 months after discontinuing the atherogenic diet (ie, the regression group). Serotonin had no effect in normal monkeys. In 18 atherosclerotic monkeys, serotonin produced transient occlusion or delayed filling of the central retinal artery and/or posterior ciliary artery (PCA) in 9 eyes of 9 animals, involving the central retinal artery in 5, lateral PCA in 8, and medial PCA in 5, in various combinations. In 6 animals (6 eyes) of the regression group, the vasoconstrictor effect of serotonin was abolished completely, except in the medial PCA in 1 eye. Serotonin, in the presence of atherosclerotic lesions, can cause transient, complete occlusion or impaired blood flow in the central retinal artery and/or PCA. We speculate that this mechanism may play a role in the development of ischemic disorders of the retina and optic nerve head. Discontinuing the atherogenic diet abolished or markedly improved the serotonin-induced vasoconstriction within a few months.

Blood flow velocity in the extraocular vessels in chronic smokers

AIMSTo determine blood flow velocity in the extraocular vessels in healthy, chronic smokers and to compare these blood flow velocities with those of healthy non-smokers.METHODSIn 46 healthy chronic smokers and...

Blood-Flow Velocities in the Extraocular Vessels in Normal Volunteers

To determine normal values of blood-flow velocities in extraocular vessels. In one eye each in 189 healthy adult volunteers, blood-flow velocities in the ophthalmic artery (OA), central retinal artery (CRA), central retinal vein (CRV), short lateral posterior ciliary artery (LPCA), and short medial posterior ciliary artery (MPCA) were measured by color Doppler imaging. In the arteries, peak systolic velocity (PSV), end diastolic velocity (EDV), and resistivity index (RI) were calculated. In the CRV, maximal and minimal blood-flow velocities were measured. Influence of age, gender, blood pressure, and heart rate on blood-flow velocities and the resistivity index were analyzed. Mean outcomes +/- S.D. cm/sec were as follows: in the OA, PSV was 39.2 +/- 5.3, EDV was 9.1 +/- 2.5, and RI was 0.77 +/- 0.05. In the CRA, PSV was 11.0 +/- 1.8, EDV was 3.3 +/- 0.9, and RI was 0.71 +/- 0.05. In the short LPCA, PSV was 11.2 +/- 1.7, EDV was 3.7 +/- 1.0, and RI was 0.68 +/- 0.06. In the short MPCA, PSV was 11.2 +/- 11.7, EDV was 3.6 +/- 0.9, and RI was 0.68 +/- 0.05. In the CRV, mean maximal velocity was 4.5 +/- 0.9, and mean minimal velocity was 3.3 +/- 0.7. Age, gender, systolic blood pressure, diastolic blood pressure, and heart rate had no consistent statistically significant influence on the measured and calculated variables. Normal values for blood-flow velocities in the extraocular vessels serve as a basis in deciding whether a measured value of a patient is normal or abnormal.

Anatomy of the ocular arteries in the horse.

Orbital and intrabulbar arteries were studied in 20 equine eyes by means of latex injections and methylmethacrylate casts. The orbital branches of the external ophthalmic artery arise far caudal to the posterior pole of the eyeball and present a variable topographic arrangement. The intrabulbar arteries are supplied by ciliary and choroidoretinal arteries. Dependent on their entrance into the eyeball, the ciliary arteries are subdivided into a posterior and an anterior group. The posterior ciliary arteries perforate the sclera post equatorially and consist of 4 major vessels that penetrate in the lateral, medial, dorsal and ventral meridian of the eyeball, respectively. The lateral and medial of these arteries follow a long intrabulbar trajectory after having supplied several short posterior ciliary arteries to the choroid. The anterior ciliary arteries consist of a dorsal and a ventral vessel which penetrate the eyeball in the pericorneal area. The choroidoretinal arteries form an arterial network around the optic nerve at the posterior pole of the eyeball. They give rise to all retinal arterioles and some peridiscal choroidal branches. The larger part of the choroid is supplied by branches of the posterior ciliary arteries. Additionally, the anterior choroid receives recurrent branches from an arterial circle that lies externally in the ciliary ring. The iris contains a major arterial circle formed by the lateral and medial long posterior ciliary arteries and both anterior ciliary arteries. A minor iridic arterial circle nor central retinal artery could be found in the equine eyes examined.

A new look at the blood supply of the retro-ocular space. Three-dimensional analysis of the arterial pattern of the posterior ciliary artery.

A study of the arterial architecture of the orbit, especially the ophthalmic artery and the course of the posterior ciliary artery in the retroocular space, was carried out in 198 cadavers by three-dimensional arteriographic analysis. The posterior ciliary arteries were classified into three types: lateral posterior ciliary, medial posterior ciliary, and accessory posterior ciliary arteries. Both the lateral and medial posterior ciliary arteries reach the eyeball in three ways: (1) they run antero-inferiorly in a winding course to the posterior margin of the eyeball, then shift upward vertically at a 60-90 degree angle and reach the eyeball, where they divide into several ciliary branches (69%); (2) after a similar course, others branch to the eyeball from the superior side (29.3%); or (3) they reach the eyeball in an almost straight course along the optic nerve (1.7%). The fundamental characteristics of these three types of posterior ciliary artery pattern also exist in subhuman primates.

Microvascular study of the retrolaminar optic nerve in man: The possible significance in anterior ischaemic optic neuropathy

The morphology of the circle of Haller and Zinn and its variations were examined using methyl-methacrylate microvascular corrosion casting of human orbits obtained at post-mortem. It was found to be an elliptical microvascular anastomosis formed by branches of the medial and lateral para-optic short posterior ciliary arteries. The ellipse was divided into superior and inferior parts by the entry points of these branches into the eye, providing an altitudinal blood supply to the retrolaminar optic nerve. Morphological variations in terms of form, position and branches existed between subjects and between eyes from the same subject. The clinical implications of an elliptical 'circle' of Haller and Zinn providing an altitudinal blood supply to the retrolaminar optic nerve are relevant to the pathogenesis of altitudinal visual field defects in anterior ischaemic optic neuropathy.

Occlusion of the posterior ciliary artery. V. Protective influence of simultaneous vortex vein occlusion.

In 28 eyes of rhesus monkeys, occlusion of all the posterior ciliary arteries (PCAs) was either performed alone (in seven eyes) or accompanied simultaneously by occlusion of one vortex vein (VV) (in 11 eyes) or two VVs (in ten eyes). In addition, in four eyes lateral PCA occlusion was combined with occlusion of two VVs. All the eyes were investigated for acute ischemic lesions in the fundus, ie, outer retinal infarcts and anterior ischemic optic neuropathy (AION). The findings indicate that occlusion of one or two VVs exercised a distinct protective influence against the acute ischemic lesions. The study also demonstrated that notable interstudy and intrastudy variations in the incidence and extent of retinal infarcts and AION among the various previously reported experimental PCA occlusion studies were caused by unintentional and unnoticed cutting of some of the VVs in the orbit.

Pulsed Doppler ultrasound for measuring blood flow velocity in the human ophthalmic circulation.

This study was performed in order to develop a method for studying blood flow in the ophthalmic circulation. Using a pulsed doppler system utilizing an ultrasonic frequency of 10 MHz, blood flow velocities have been measured in the ophthalmic artery and in the arteries behind the eyeball (lateral posterior ciliary arteries) in 40 normal subjects. The mean of the peak systolic velocities were 34 +/- 6 cm/s in the ophthalmic artery, and 14 +/- 3 cm/s in the lateral posterior ciliary arteries. We conclude that blood flow velocities can be measured in defined vessel areas in the orbit.

Choroidal Blood Flow

The effect of vasodilators on choroidal blood flow (CBF) was studied by the krypton clathrate Kr 85 desaturation technique in anesthetized cats. Niacin, papaverine hydrochloride, phentolamine mesylate, and tolazoline hydrochloride were injected via the lateral long posterior ciliary artery (LLPCA) and the femoral artery. The systemic administration of these drugs via the femoral artery, in the doses used, had no significant effect on mean arterial pressure, choroidal vascular resistance (CVR), or CBF. Local administration of the same agents via the LLPCA caused a decrease in CVR with a corresponding increase in CBF.

Phagocytic activity in the ischemic retinal pigment epithelial cells

The role of lysosomal enzymes in ischemic retinal pigment epithelial cells (RPE) of albino rabbits was examined with the modified Gomori technique for acid phosphatase. Ischemia was produced by cutting the lateral posterior ciliary artery and short posterior ciliary arteries (PCA). Five days after PCA-cut RPE in the ischemic region were disorganized by increased enzymatic digestion. In RPE of the border between the ischemic and normal region a lot of fragmented outer segments were phagocytosed 24 h to 7 days after PCA-cut. At this time phagosomes appeared much more frequently than in the normal retina, showing several variations in their shape, localization, and histochemical reaction. However, after 10 and 14 days, RPE in the border had a tendency to reduce the phagocytic activity. A strong acid phosphatase activity was encountered in the phagosomes of macrophages, which was considered to be derived from RPE, and seemed to play the major role in scavenging destructed retinal elements.

Choroidal blood flow. II. The effects of autonomic agents.

The effects of autonomic agents on the choroidal circulation were studied by the radioactive krypton desaturation technique in anesthetized cats. Levarterenol, epinephrine, and acetylcholine, when administered locally via the lateral long posterior ciliary artery (LLPCA), caused the anticipated changes in choroidal vascular resistance (CVR), and corresponding changes in choroidal blood flow (CBF). When administered systemically via the femoral artery, the changes in the mean arterial pressure (MAP) tended to mask any changes in CVR resulting in an opposite effect on CBF. Isoproterenol was found to have no effect on CBF when administered via the LLPCA; when injected via the femoral artery, it resulted in a decrease in MAP and CBF without a significant change in CVR.

The orbital vessels of rhesus monkeys

The orbital vessels in rhesus monkeys were studied. The arterial supply is by the ophthalmic artery, a branch of the internal carotid artery in the cranial cavity. The ophthalmic artery gives multiple branches throughout its entire course: from the intracranial part, a prominent ophthalmic communicating artery; from the intracanalicular part, one or more branches; from the intraorbital part, the central retinal artery, lateral posterior ciliary artery, lacrimal artery, branch to superior rectus, medial muscular artery in common with medial posterior ciliary arteries, branch to medial rectus, ethmoidal artery, branch to levator palpebrae superioris, medial palpebral artery, diploic branch, and terminal branches (supraorbital, supratrochlear and, rarely, dorsal nasal), generally in that order from the proximal to the distal part of the artery. Their origin, course and supply are discussed. The arterial pattern of rhesus monkeys is compared with that of human beings. The venous drainage is by superior and inferior ophthalmic veins which join together near the superior orbital fissure to open ultimately in the cavernous sinus. Tributaries of each vein are described with particular reference to the ocular veins.