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PubMed1978

[Ophthalmocalibrometric assessment of the state of the microcirculation in the retinal vessels in transient disorders of cerebral circulation].

The report analyses some results of a neuro-ophthalmological study of 82 patients from 34--76 years (37 males and 45 females) with transient disorders of cerebral circulation. Besides clinical studies the authors applied EEG and REG registrations, studies of the lipid metabolism, coagulative and anticoagulative blood systems. Ophthalmological studies included the assessment of visual acuity with and without correction, quantitative perimetry, the determination of a genuine intra-ocular pressure, ophthalmodynamometry, biomicroscopy of the conjunctiva and episclera, biomicro-ophthalmoscopy, ophthalmoscopy with the use of electro-ophthalmoscopy, a large nonreflex ophthalmoscope, ophthalmocalibrometry. By means of ophthalmocalibtometrical studies the authors established an existence of expressed pathology of microcirculation in the form of a marked narrowing of arterioles and a dilatation of the venoules with a significant decrease of the arterio-venous correlations. The achieved data are analyzed with consideration of the etiology, development and topography of transient disorders of cerebral circulation.

Adult↗
PubMed2005

Do complaints of amaurosis fugax and blurred vision after transcatheter device closure of atrial septal defect indicate microemboli to retinal vessels?

Atrial septal defect (ASD) is a common diagnosis in adults undergoing surgical repair. The aim of the study was to determine if ocular symptoms following treatment are due to microemboli. The study group included 20 adult patients (9 men, 11 women, mean age 57.2 years) with ASD who had undergone successful closure with the Amplatzer occluder. Patients were treated with aspirin or warfarin during the 6 months after the procedure. All were evaluated neurologically and an ocular medical history was obtained. Ocular examination included the 120-point Humphery visual field. Transcranial Doppler (TCD) was performed to monitor the middle cerebral artery. Two patients complained of amaurosis fugax at 1 and 3 months after the procedure, and two patients complained of blurred vision at 3 and 4 months after the procedure. TCD performed within 24 h of the complaints revealed no abnormalities. In all patients, the neurological and ocular examinations, including the visual field test, were normal. In conclusion, microembolic events do not appear to be the cause of the ocular complaints in patients with ASD treated with Amplatzer occluder. Further studies in larger samples are needed to confirm these results.

Adult↗
PubMed1995

Vascular endothelial growth factor acts as a survival factor for newly formed retinal vessels and has implications for retinopathy of prematurity.

Retinopathy of prematurity (ROP) is initiated by hyperoxia-induced obliteration of newly formed blood vessels in the retina of the premature newborn. We propose that vessel regression is a consequence of hyperoxia-induced withdrawal of a critical vascular survival factor. We show that regression of retinal capillaries in neonatal rats exposed to high oxygen, is preceded by a shut-off of vascular endothelial growth factor (VEGF) production by nearby neuroglial cells. Vessel regression occurs via selective apoptosis of endothelial cells. Intraocular injection of VEGF at the onset of experimental hyperoxia prevents apoptotic death of endothelial cells and rescues the retinal vasculature. These findings provide evidence for a specific angiogenic factor acting as a vascular survival factor in vivo. The system also provides a paradigm for vascular remodelling as an adaptive response to an increase in oxygen tension and suggests a novel approach to prevention of ROP.

Animals↗
PubMed1988

[Parapapillary diameter of retinal vessels. I. Estimating the size of the optic papilla (a papillometric study of over 264 normal eyes)].

The diameter of the temporal superior and inferior retinal artery and vein were measured at the optic disk border and 2 mm from the disk center in 264 nonselected normal eyes on the basis of photographs, with correction of magnification. Additionally, the individual ocular magnification factor was determined by Littmann's method. The mean caliber of the artery was 0.113 +/- 0.019 mm at the disk border and 0.118 +/- 0.023 2 mm from the disk center. The corresponding values for the vein were 0.149 +/- 0.026 mm and 0.159 +/- 0.026 mm. The correlations between vessel caliber and disk size were not significant, but the relationship between disk size and the quotient of vessel diameter divided by disk size was highly significant (p less than 0.0001). Vessel diameter can therefore be taken as an independent unit for determining optic disk size in relative and approximately also in absolute units. Thus, mean horizontal disk diameter (1.77 +/- 0.33 mm) corresponded to 16.3 +/- 3.5 artery and 12.3 +/- 2.6 vein diameters (measured at the optic disk border). The mean individual ocular magnification factor was 0.302 +/- 0.017, with a Gauss standard distribution. If the optical characteristics of a photographed eye are not known and the ocular magnification factor is assumed to be 0.302, then 68.3% of all eyes will be covered with an inaccuracy of 5.6% and 95.5% of all eyes with an inaccuracy of 11.2%.

Adolescent↗
PubMed1989

Blood pressure, intraocular pressure, and retinal vessels after high altitude mountain exposure.

Identical test protocols were used before and after 2 to 7 weeks of high altitude exposure in 23 climbers participating in 3 separate mountain expeditions in the Himalayas. The three groups reached altitudes of 4,000 m, 5,200, and 5,850 m, respectively. High altitude retinal hemorrhages (HARH) were found in three subjects (13%). Two weeks after the mountain exposure, reduced mean values of systolic (p less than 0.005) and diastolic (p less than 0.05) blood pressure and intraocular pressure (p less than 0.005) were found. Retinal veins were dilated 2.6% (p less than 0.001), and in both arteries (p less than 0.001) and veins (p less than 0.005) we observed a tendency for small vessels to dilate and large vessels to constrict. The intensity of reflection of light ("the central light reflex") from arteries was reduced (p = 0.003), indicating hemorrheology changes in the vessels. This study shows that significant changes in blood pressure, intraocular pressure and retinal vascularity follow hypoxic and physical strain of high altitude. The vascular conditioning of altitude acclimatization can be demonstrated in the retinal circulation 2 weeks after the exposure.

Adult↗
PubMed1998

The 67-kd laminin receptor is preferentially expressed by proliferating retinal vessels in a murine model of ischemic retinopathy.

Endothelial cell association with vascular basement membranes is complex and plays a critical role in regulation of cell adhesion and proliferation. The interaction between the membrane-associated 67-kd receptor (67LR) and the basement membrane protein laminin has been studied in several cell systems where it was shown to be crucial for adhesion and attachment during angiogenesis. As angiogenesis in the pathological setting of proliferative retinopathy is a major cause of blindness in the Western world we examined the expression of 67LR in a murine model of hyperoxia-induced retinopathy that exhibits retinal neovascularization. Mice exposed to hyperoxia for 5 days starting at postnatal day 7 (P7) and returned to room air (at P12) showed closure of the central retinal vasculature. In response to the ensuing retinal ischemia, there was consistent preretinal neovascularization starting around P17, which persisted until P21, after which the new vessels regressed. Immunohistochemistry was performed on these retinas using an antibody specific for 67LR. At P12, immunoreactivity for 67LR was absent in the retina, but by P17 it was observed in preretinal proliferating vessels and also within the adjacent intraretinal vasculature. Intraretinal 67LR immunoreactivity diminished beyond P17 until by P21 immunoreactivity was almost completely absent, although it persisted in the preretinal vasculature. Control P17 mice (not exposed to hyperoxia) failed to demonstrate any 67LR immunoreactivity in their retinas. Parallel in situ hybridization studies demonstrated 67LR gene expression in the retinal ganglion cells of control and hyperoxia-exposed mice. In addition, the neovascular intra- and preretinal vessels of hyperoxia-treated P17 and P21 mice labeled strongly for 67LR mRNA. This study has characterized 67LR immunolocalization and gene expression in a murine model of ischemic retinopathy. Results suggest that, although the 67LR gene is expressed at high levels in the retinal ganglion cells, the mature receptor protein is preferentially localized to the proliferating retinal vasculature and is almost completely absent from quiescent vessels. The differential expression of 67LR between proliferating and quiescent retinal vessels suggests that this laminin receptor is an important and novel target for future chemotherapeutic intervention during proliferative vasculopathies.

Animals↗
PubMed1993

In vivo micropuncture of retinal vessels.

Micropuncture has proven to be a valuable tool for the local study of vascular parameters in many organ systems; however, it has not been applied to the study of the circulation of the retina. We report here our extension of micropuncture techniques [4] to use in the intact retina of the anesthetized cat. We use extremely sharp micropipettes with tip sizes much smaller than the diameter of erythrocytes to avoid hemorrhage. The micropipette is held by a microdrive which in turn is mounted on a precision goniometric micromanipulator. We micropuncture retinal arteries and veins with diameters ranging from 20 to 130 microns with no apparent damage to the vessel wall and no observed hemorrhage. During micropuncture we routinely inject nanoliter quantities of dyed saline, which we observe flowing in a plume from the micropipette tip within the lumen of the vessel. Micropuncture techniques may be used in the laboratory to study retinal autoregulatory mechanisms by microinfusion of vasoactive substances and by measuring blood pressure in retinal microvessels. In the clinic micropuncture may be useful for treating disorders such as retinal vascular occlusion.

Animals↗
PubMed1989

Carotid arteries in central retinal vessel occlusion as assessed by Doppler ultrasound.

Doppler ultrasound was used to detect possible flow changes in the carotid arteries of patients with central retinal artery and vein occlusion. Twenty-three patients with central retinal artery occlusion (mean age 56, SD 11, years) were examined 4 to 48 months after the development of the occlusion and compared with age and sex matched control subjects with no history of any disease known to be associated with pathological changes in carotid vessels. Significant stenosis or occlusion of one or more carotid arteries was discovered in eight patients with retinal artery occlusion, while the ultrasonic findings were normal in all the controls (p less than 0.005). Blood flow was evaluated by the same method in 16 patients with central retinal vein occlusion (mean age 57, SD 9, years) six to 48 months after the event. A control group was chosen according to the same criteria as in previous comparison. Pathological ultrasonic findings were observed neither in the patients with retinal vein occlusion nor in the control group. The results suggested a possible aetiological relation between pathological changes in the carotid arteries and occlusion of the central retinal artery, but not occlusion of the central retinal vein.

Arterial Occlusive Diseases↗
PubMed2006

Intravascular oxygen saturation in retinal vessels in normal subjects and open-angle glaucoma subjects.

PURPOSE: To measure the oxygen saturation (SO(2)) in retinal arterioles and venules in patients with glaucomatous optic neuropathy. METHODS: We examined SO(2) in retinal arterioles and venules simultaneously by imaging spectrometry. Oxygen saturation was evaluated according to the difference of the extinction spectra of haemoglobin and oxyhaemoglobin. The arterio-venous difference (avD) was calculated by (SO(2art) - SO(2ven)). The optic nerve head topography was estimated by Heidelberg retinal tomography and the visual field using the Octopus G1. We examined one eye in each of 58 healthy persons (mean age 58.6 +/- 10.7 years; mean rim area 1.52 +/- 0.33 mm(2); mean defect 0.65 +/- 1.31 dB; mean intraocular pressure [IOP] 18.5 +/- 2.7 mmHg), 49 patients with normal-tension primary open-angle glaucoma (NTG) (mean age 63.0 +/- 8.5 years; mean rim area 0.89 +/- 0.34 mm(2); mean defect 5.4 +/- 4.1 dB; mean IOP 19.2 +/- 2.9 mmHg), and 45 patients with high-tension primary open-angle glaucoma (POAG) (mean age 62.6 +/- 10.3 years; mean rim area 0.97 +/- 0.47 mm(2); mean defect 7.1 +/- 6.4 dB; mean IOP 31.6 +/- 10.8 mmHg). RESULTS: The intraclass correlation coefficients of the SO(2) measurement were 0.82 (arteriole) and 0.59 (venule). In normal eyes, the SO(2art), SO(2ven) and avD were 92.3 +/- 3.4%, 55.7 +/- 6.8% and 36.6 +/- 7.0%, respectively. Equivalent data were 89.7 +/- 5.4%, 56.0 +/- 8.3% and 33.7 +/- 10.6%, respectively, in NTG eyes and 91.4 +/- 4.0%, 58.3 +/- 10.5% and 33.1 +/- 11.5%, respectively, in POAG eyes. Over all examined eyes, the arteriolar SO(2) and the retinal arterio-venous difference correlated significantly with the rim area. CONCLUSION: Eyes with NTG showed significantly decreased arteriolar SO(2). These changes were not seen in POAG patients.

Glaucoma, Open-Angle↗
PubMed2003

Retinal vessel diameters and their associations with age and blood pressure.

PURPOSE: To describe the cross-sectional relationship between retinal arteriolar and venular diameters with age and blood pressure. METHODS: A population-based study was conducted in Beaver Dam, Wisconsin (n=4926, age range, 43-84 years). Retinal photographs of right eyes taken at the baseline examination (1988-90) were digitized. All arterioles and venules located in the area between one-half and one disc diameter from the optic disc margin were measured with a computer-based program. These measurements were combined to provide the average diameters of retinal arterioles and venules of each eye, and the association with age and blood pressure (BP) was analyzed. RESULTS: After controlling for gender, hypertension, diabetes, serum glucose and lipids, cigarette smoking, and body mass index, retinal arteriolar diameters were found to be decreased by 2.1 microm (95% confidence interval [CI], 1.5-2.7) for each decade increase in age, and by 4.4 microm (95% CI, 3.8-5.0) for each 10-mm Hg increase in mean arterial BP. The association of narrowed retinal arterioles and higher BP was stronger in younger persons. For each 10-mm Hg increase in mean arterial BP, arteriolar diameters decreased by 7.0 microm in persons aged 43 to 54 years but by only 2.5 microm in persons aged 75 to 84 years. In contrast, retinal venular diameters narrowed with increasing age but not with increasing BP. CONCLUSIONS: Retinal arteriolar diameters are narrower in older persons and in persons with higher BP, independent of other factors. The weaker association of retinal arteriolar diameters and BP in older people may reflect greater sclerosis of the retinal arterioles, preventing a degree of narrowing with higher BP similar to that seen in younger persons.

Adult↗
PubMed1998

Immediate response of retinal vessels to isometric muscle contraction.

Isometric muscle contraction results in a rise in systemic blood pressure (BP) and constriction of retinal arterioles. The responses in the anaesthetised cat have been studied to provide further insight into the results of human studies. Constriction (median 3.43% of control values) and dilatation (median 4.17% of control values) were observed; the onset of constriction was delayed by 4 s compared with dilatation. There was spatial and temporal variation in the observed calibre changes, and inter-experimental variation in the calibre change/BP ratio. It is concluded that the response of retinal arterioles of measurable size is not unified, and that the two modes of response differ in mechanism.

Animals↗
PubMed1993

Analysis of vasocontractile responses to endothelin-1 in rabbit retinal vessels using an ETA receptor antagonist and an ETB receptor agonist.

To study the role of endothelin receptor subtypes in rabbit retinal arteries, endothelin-1 (ET-1)-induced vasoconstriction was analyzed using the ETA receptor antagonist BQ-123 and the ETB receptor agonist BQ-3020. A cumulative injection of ET-1 (1 approximately 100 pmole) into the posterior vitreous body in anesthetized rabbits caused dose-dependent vasoconstriction in the retinal arteries, and ultimately caused complete obstruction. Fifteen minutes after BQ-123 (1 mumole) was injected into the posterior vitreous body, the dose-response curve of ET-1 was significantly shifted to the right. Intravitreal injection of BQ-3020 caused a significant retinal vasoconstriction only at the highest dose (1000 pmole). Therefore, in rabbit retinal arteries, ET-1-induced vasoconstriction appears to be mediated mainly through ETA receptors.

Animals↗
PubMed1981

A model of experimental atherosclerosis in pigs. Part III. Electroretinography and the diameter of retinal vessels.

Domestic pigs were fed with high lipid diet (HLD) for 24 weeks. Electroretinographic studies and the measurement of the diameter of retinal arterioles were investigated before and after the administration of HLD. The most significant change produced by HLD was negativization of electroretinogram. At the same time the diameter of retinal arterioles was significantly decreased.

Animals↗
PubMed2006

Effect of acidosis on isolated porcine retinal vessels.

PURPOSE: To study the effect of normocapnic (NA) and hypercapnic acidosis (HA) on the tone, the intracellular calcium level ([Ca(2 +)](i)), and the membrane potential of smooth muscle cells in porcine retinal arterioles. METHODS: Twenty-four porcine retinal arterioles were mounted in a wire myograph for isometric recording of the wall tension. The vessels were precontracted with 0.3 microM U46619 and were exposed to NA (pH = 7.0) and HA (pH = 7.0). Intracellular calcium was measured using the fluorophore Fura-2AM (n = 12). In six vessels, 0.1 mM NG-nitroarginine methyl ester (L-NAME) was added to block NO synthesis. The membrane potential of smooth muscles cells was measured in situ with sharp glass electrodes (n = 12). RESULTS: NA and HA induced both a decrease in wall tension from 1.04 +/- 0.06 N/m to 0.65 +/- 0.1 N/m (p < 0.01) (NA) and 0.56 +/- 0.1 N/m (p < 0.01) (HA) and a decrease in [Ca(2 +)](i) as evidenced from the change in the Fura-2 fluorescence emission ratio from 0.66 +/- 0.03 to 0.57 +/- 0.05 (p = 0.005) (NA) and 0.56 +/- 0.05 (p = 0.002) (HA). These results were unaffected by inhibition of NO-synthesis. NA and HA also both induced hyperpolarization of the smooth muscle membrane from -18 +/- 0.7 mV during precontraction to -26 +/- 1.9 mV (p = 0.002) (NA) and -24 +/- 2.6 mV (p = 0.02) (HA). CONCLUSIONS: Acidosis-induced relaxation of the tone in preconstricted isolated porcine retinal arterioles is associated with a decrease in intracellular calcium and a hyperpolarization of the smooth muscle cells. The acidosis-induced relaxation is independent of CO(2) and is not mediated through NO.

Acidosis↗