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At least 145 records · Page 8Linked to original sources
PubMed1990

Ultrastructural localization of extracellular matrix components in human retinal vessels and Bruch's membrane.

We have used the electron microscopic immunogold technique to localize precisely various extracellular matrix components in human retinal vessels and Bruch's membrane. Collagen types IV and V, laminin, and heparan sulfate proteoglycan core protein were localized in basement membranes of retinal capillaries. In addition to the capillary basement membrane components, collagen types I and III and fibronectin were found in the basement membranes of retinal arterioles and venules. The basement membranes of choriocapillaries and retinal pigment epithelial cells in Bruch's membrane also showed a similar distribution of the retinal capillary basement membrane components. Both the inner and outer collagenous layers of Bruch's membrane contained collagen types I and III along with fibronectin, whereas collagen type VI was mostly limited to the central elastic lamina. The precise localization and distribution of various extracellular matrix components in human retinal vessels and Bruch's membrane may be important for understanding their normal function as well as their alteration in disease.

Aged↗
PubMed1993

[Tortuous retinal vessels].

The authors observed an occurrence of tortuosity of retinal vessels from the group of 5,000 investigations of an ocular fundus. Elimination of all local reasons or symptoms of general diseases, even in spite of the great possibility of modification of this feature, three characteristic types were found. In two of them the familiar and hereditary occurrence was proved.

Congenital Abnormalities↗
PubMed1985

Facioscapulohumeral dystrophy with cochlear hearing loss and tortuosity of retinal vessels.

We report on a mother and her three children with facioscapulohumeral dystrophy (FSHD), sensorineural hearing loss, and marked tortuosity of the retinal vessels. Initially the children presented with speech difficulties and hearing deficit. Hearing loss ranged from mild to severe. An audiologic evaluation, including brain stem auditory evoked responses in all patients, indicated a cochlear origin of hearing loss and intact pathways from the cochlea to the temporal lobe. The association of FSHD with hearing loss and tortuosity of the retinal vessels suggests previously unrecognized pleiotropy of FSHD (McKusick 15890) or a "new" type of FSHD.

Adolescent↗
PubMed1992

Retinal vessel measurement: comparison between observer and computer driven methods.

A method of semi-automated image analysis for the measurement of retinal vessel diameters is described. This was compared with an observer-driven method for reproducibility and accuracy. The coefficient of variation for the data from the semi-automated method was 1.5-7.5% (depending on the vessel diameter) compared to 6-34% with the observer-driven method. The mean vessel diameters using the observer-driven method tended to be higher; however, this did not reach significance. The speed and low inter- and intra-observer variability for the semi-automated method make it a useful technique for measuring retinal blood vessel diameters. A larger variability was found between photographs taken at different times. This may be due to changes in retinal vessel diameter with changes in retinal perfusion pressure during the cardiac cycle.

Diabetic Retinopathy↗
PubMed1999

Angiotensin II-induced constrictions are masked by bovine retinal vessels.

PURPOSE: To unmask the vasoconstricting effect of angiotensin II (Ang II) on retinal smooth muscle by studying its interaction with endothelium-derived paracrine substances. This study focused specifically on determining the changes in vascular diameter and the release of endothelial-derived vasodilators, nitric oxide (NO) and prostaglandin (PG) I2, from isolated retinal microvessels. METHODS: Bovine retinal central artery and vein were cannulated, and arterioles and venules were perfused with oxygenated/heparinized physiological salt solution at 37 degrees C. This ex vivo perfused retinal microcirculation model was used to observe the contractile effects of Ang II on arterioles and venules of different diameters. The NO and PGI2 synthase inhibitors, 1-NOARG and flurbiprofen, respectively, were used to unmask Ang II vasoconstriction; the changes in vascular diameters were then measured. Enzyme immunoassays were used to measure the release of cGMP (an index of NO release) and 6-keto-PG-F1alpha (a stable metabolite of PGI2) from isolated bovine retinal vessels. RESULTS: Topically applied Ang II (10(-10) M to 10(-4) M) caused significant (P < 0.05) arteriolar and venular constrictions in a dose-dependent manner, with the smallest retinal arterioles (7+/-0.2 microm luminal diameter) and venules (12+/-2 microm luminal diameter) significantly more sensitive than larger vessels. After the inhibition of endogenous NO and PGI2 synthesis by 1-NOARG and flurbiprofen, respectively, the vasoconstriction effects of Ang II became more pronounced. Again, the smallest vessels tested were significantly more sensitive, and synthesis of endothelial-derived relaxing factor (EDRF), therefore, may be most important in these vessels. Vasoactive doses of Ang II (10(-10) M to 10(-4) M) caused a dose-dependent increase in the release of NO and PGI2 from isolated bovine retinal vessels, indicating that the increase in EDRF may nullify direct Ang II-induced vasoconstriction. Interestingly, intraluminal administration of Ang II caused only vasodilation. CONCLUSIONS: This study demonstrates that the retinal vascular endothelium acts as a buffer against the vasoconstricting agent Ang II via release of vasodilators NO and PGI2, and the vasoconstriction effects due to Ang II are most prominent in the smallest diameter vessels.

6-Ketoprostaglandin F1 alpha↗
PubMed2005

Retinal vessel diameters and cerebral small vessel disease: the Rotterdam Scan Study.

The direct visualization of retinal vessels provides a unique opportunity to study cerebral small vessel disease, because these vessels share many features. It was reported that persons with smaller retinal arteriolar-to-venular ratio tended to have more white matter lesions on MRI. It is unclear whether this is due to arteriolar narrowing or venular dilatation. We investigated whether smaller arteriolar or larger venular diameters or both were related to severity and progression of cerebral small vessel disease. We studied 490 persons (60-90 years) without dementia from a population-based cohort study. At baseline (1990-1993), retinal arteriolar and venular diameters were measured on digitized images of one eye of each participant. In 1995-1996, participants underwent cerebral MRI scanning. We rated the severity of periventricular white matter lesions on a 9-point scale, approximated a total subcortical white matter lesion volume (range: 0-29.5 ml) and rated the presence of lacunar infarcts. On average 3.3 years later, 279 persons had a second MRI. Changes in periventricular and subcortical white matter lesions were rated with a semi-quantitative scale, and progression was classified as no, minor and marked. An incident infarct was a new infarct on the follow-up MRI. Neither venular nor arteriolar diameters were related to the severity of cerebral small vessel disease. Larger venular diameters were, however, associated with a marked progression of cerebral small vessel disease. Age and gender adjusted odds ratios (ORs) per standard deviation increase were 1.71 [95% confidence interval (CI): 1.11-2.61] for periventricular, 1.72 (95% CI: 1.09-2.71) for subcortical white matter lesion progression and 1.59 (95% CI: 1.06-2.39) for incident lacunar infarcts. These associations were independent of other cardiovascular risk factors. Only the OR for incident lacunar infarcts was attenuated (1.24; 95% CI: 0.72-2.12). No association was observed between arteriolar diameters and progression of cerebral small vessel disease. In conclusion, retinal venular dilatation was related to progression of cerebral small vessel disease. The mechanisms underlying venular dilatation deserve more attention, as they may provide new clues into the pathophysiology of cerebral small vessel disease.

Age Factors↗
PubMed1991

Measurement of blood flow velocity in retinal vessels utilizing laser speckle phenomenon.

The laser speckle phenomenon was applied to the measurement of the blood flow velocity in glass capillary tubes and human retinal vessels. The instrument consists of a fundus camera, a He-Ne laser, a photomultiplier, a photon-counting unit, a digital correlator, and a microcomputer system. The scattered laser beam from the retina was detected by the photomultiplier and these signals were processed by the photon-counting unit. The digital correlator and the microcomputer calculated the autocorrelation function of these processed signals. The power of the laser beam was 18 mW/cm2, which was sufficiently below the minimum level considered hazardous to the retina. This technique did not require fine optical alignment and the measurement could be done in 1.05 seconds. A linear relationship between the blood flow velocities in glass capillary tubes and the reciprocal of the correlation time was proved, and the pulsatile flow of a human retinal artery was demonstrated. The reproducibility of the method was 12.4 +/- 6.5% in arteries (Mean +/- SD, n = 4) and 12.4 +/- 5.1% in veins (Mean +/- SD, n = 16). The mean blood flow rate in retinal vessels obtained in this experiment agreed with the values of previous studies. This technique utilizing the laser speckle phenomenon is useful in clinical application to measure the retinal blood flow velocity.

Adult↗
PubMed1980

Permeability changes in cerebral, iridic, and retinal vessels during experimental decompression sickness in the rat.

An investigation has been made of the effect of acute decompression sickness upon the permeability of the cerebral, iridic, and retinal vessels of the rat, with sodium-fluorescein as intravenous tracer. No permeability changes were observable during the first 15 min subsequent to decompression, following exposure to 5.1 bar for 50 min. Focal leaky areas were found in the brain parenchyma after exposures to 5.1 bar for 120 min. Although sodium-fluorescein partially permeated the pial vessels in controls, the treatment in a hyperbaric chamber seems to increase the diffusion of the tracer from the pia into the cerebral cortex. Nevertheless, both the iridic and retinal vessels remained "tight." The factors which increase the permeability of microvasculature in brain and possible reasons for the negative results obtained with the iris and retina in decompression sickness are discussed.

Air Pressure↗
PubMed1988

Immunocytochemical localization of laminin, type IV collagen and fibronectin in rat retinal vessels.

Laminin, type IV collagen and fibronectin have been identified as major components of the basement membrane (basal lamina) in various tissues. These antigens have also been identified in retinal vessels by light microscopic immunofluorescence but their precise location could not be determined at this level of resolution. In this study, we examined the localization of these constituents at the ultrastructural level using the protein A-immunoperoxidase technique. The basal lamina of all retinal capillaries, arterioles and venules was immunostained after exposure to antisera against laminin, type IV collagen and fibronectin. Staining was localized to the lamina densa, which appeared as a single or double layer. Immunostaining for fibronectin showed the weakest activity. The reaction was also seen in discrete patches between endothelial cells and pericytes. The inner limiting membrane of the retina was also reactive for laminin and type IV collagen but not for fibronectin. The results indicate that laminin, type IV collagen and fibronectin are components of the basal lamina in all types of retinal vessels. The presence of fibronectin at the endothelial-pericyte interface suggests that this protein may promote adhesion between cells and thus help to maintain the integrity of the vessel wall.

Animals↗
PubMed2000

[Optical Doppler velocimetry of red blood cells at different depths in retinal vessels by varying the coherence length of the source: feasibility study].

PURPOSE: To report on a novel approach to measure the velocity of red blood cells (RBCs) at different retinal vessel depths. METHOD: The technique is an extension of conventional laser Doppler velocimetry using light sources of various coherence lengths (CL). Light scattered by the moving RBCs interferes with that reflected from the anterior vessel wall only if the optical path difference is shorter than CL. Therefore, using low coherence light sources, localized measurements of RBCs velocity can be performed. RESULTS: Measurements of RBCs velocity at different depths in a main retinal vein (diameter: 152 microns) of a volunteer has been performed using 4 different light sources with CLs of 14 microns, 21 microns, 32 microns and > m. Measured values are in good agreement with theoretically predicted values. CONCLUSION: This new approach permits to measure RBCs velocity at different depths of retinal vessels in the human retina.

Blood Flow Velocity↗
PubMed1977

[The possible connection between the occurrence of embolism and thrombosis in the retinal vessels and the weather (author's transl)].

While in the comparatively short period of three months (middle Febraury to end of May 1976) embolisms and thromboses of the retinal vessels were suddenly observed much more commonly in the University Eye clinic in Münster we tried to discover a possible connection with the weather. All patients had conditions which predisposed to thrombo-embolic occlusive vascular disease. We use the decimal classification of weather, and on the basis of this we could prove a connection between the intensity of the start of the thromboembolic process and cyclonic and anticyclonic weather situations and situations which favour allergic-hyperergic reactions to inflammatory processes. In venous occlusion an increase in the impulse number in the area (0,02 V/m) and hence increased thrombocyte adhesion at the beginning of the thrombotic process seemed to be the deciding factor. We made comparisons with the literature. It seems to be ophthalmologically important that also increase in the light intensity can be associated with thrombo-embolic occlusions in the retinal vessels.

Adolescent↗
PubMed1995

Direct measurement of retinal vessel diameter: comparison with microdensitometric methods based on fundus photographs.

A new method for the direct measurement of retinal vessel diameter was developed and the results were compared with those of two computer-assisted semiautomatic microdensitometric methods. The direct measurement method was based on automated detection of vessel edges by processing the one-dimensional retinal image obtained by a linear image sensor set in a fundus camera; results are obtained in real-time. Thirty-eight points on 36 vessels (15 points on arteries and 23 points on veins) of two normal volunteers (four eyes) were selected as the measurement points. Two observers measured the vessel diameters at these points and the interobserver variation of the direct method and the microdensitometric methods was compared. The coefficient of variation and the interobserver variation of the direct method for all measurements were 1.71 + 1.13% and 2.25 + 1.92%, respectively. There was no significant difference between the measured values for the two observers with the direct method (paired t-test, P > 0.05), and the interobserver variation of the direct method was smaller than those of the microdensitometric methods. This newly developed direct method for measurement of retinal vessel diameter not only avoids systematic errors that result from film development or the characteristics of the film, but also generates reproducible results in real-time and small interobserver variation.

Adult↗
PubMed1992

Aplasia of the retinal vessels combined with optic nerve hypoplasia, neonatal epileptic seizures, and lactic acidosis due to mitochondrial complex I deficiency.

A newborn male with mitochondrial complex I deficiency suffered from neonatal epileptic seizures, which later developed into infantile spasms. The infant was blind due to aplasia of the retinal vessels and hypoplasia of the optic nerve. There was congenital lactic acidosis, which persisted in later life. The boy was microcephalic and retarded. Muscular hypotonia later shifted to spasticity. Succinic acid was increased in urine. We assume that the aplasia of the retinal vessels is due to damage of the retinal ganglion cells caused by the mitochondrial disease in the first 3 to 4 months of pregnancy.

Acidosis, Lactic↗
PubMed1990

Microvascular network topology of the human retinal vessels.

A quantitative analysis of blood flow in the human retinal vessels requires a detailed picture of the microvascular network topology. In order to lay the foundation for a quantitative microcirculatory network analysis of the human retina, a novel technique for tissue preparation and network characterization was developed. After injection of hydrogen peroxide into the human bulb, the microvasculature was filled with oxygen produced by endothelial catalase and visualized after embedding in a mixture of cedar oil and gum damar. The vessel topology was documented in the form of photomicrographs, which permitted complete reconstruction of the microvasculature on transparent overlays. By considering the complete capillary system it was possible to divide the retinal network into dichotomous, asymmetric arteriolar and venular trees. The Strahler ordering method, which considers both dichotomous and side branching configurations, was selected and applied to analyze the retinal vascular trees, using the capillaries as the zero order reference vessels. The number of vessel segments was found to be an approximate logarithmic function of the order number, in accordance with Horton's law. Vessel lengths within each order were found to be log-normal distributed, and median lengths for different orders could be approximated by a 2nd degree polynomial curve. Diameters within each order could be approximated by a Gaussian distribution, and the mean values for different orders could be expressed by an exponential curve. These data provide the basis for conductance, pressure and flow computations within the retinal microvessels.

Arteriovenous Anastomosis↗
PubMed2006

Short-term retinal vessel diameter variability in relation to the history of cold extremities.

PURPOSE: To test whether the regularity and short-term changes of retinal vessel diameter are related to the history of cold hands and feet and to nailfold circulatory response to cooling. METHODS: In 13 vasospastic and 13 nonvasospastic young healthy women (based on their history of cold extremities and nailfold capillaroscopy) 20- to 30-second recordings of the ocular fundus was obtained with a retinal vessel analyzer. The spatial regularity of arterioles and venules was analyzed by means of the coefficient of variation of vessel diameter and by exploratory Fourier analysis of spatial frequencies. Temporal variability was analyzed as excursion amplitude of the vessel diameter, as a correlation of means and standard deviations of vessel diameter within a defined time period, and by Fourier analysis of temporal diameter change in the heartbeat frequency range. RESULTS: Mean diameters of selected segments of arterioles (129.9 +/- 15.3 and 124.4 +/- 24.4 microm) and venules (150.8 +/- 14.6 and 149.3 +/- 19.6 microm) were not different between the vasospastic and nonvasospastic groups, respectively. Spatial variability: The coefficient of variation in arterioles was 8.8% +/- 2.8% and 6.1% +/- 1.7%, in venules 3.8% +/- 1.4%, and 3.6% +/- 0.9% in the vasospastic and nonvasospastic groups, respectively (difference by ANOVA, P = 0.017). Fourier analysis revealed differences between arterioles in the two groups, with relative Fourier power spectrum amplitudes of spatial frequencies higher in vasospastic eyes (Mann-Whitney P = 0.029). Temporal variability: The excursion amplitudes of vessel diameters were comparable in the two groups. Individual coefficients of correlation of successive means and standard deviations of the vessel diameter were 0.11 +/- 0.23 and 0.09 +/- 0.23 in the nonvasospastic group, and 0.25 +/- 0.40 and 0.24 +/- 0.22 in the vasospastic group, in the arterioles and venules, respectively (ANOVA: vasospastic versus nonvasospastic; P = 0.038). Fourier analysis in the heartbeat frequency range revealed differences in relative power spectrum amplitudes of temporal frequencies between arterioles in the two groups (higher in the vasospastic group, Mann-Whitney P = 0.029). CONCLUSIONS: Retinal arterioles in healthy vasospastic women show higher spatial irregularity and an increased vessel diameter variation within the temporal frequency of the heartbeat than do arterioles in nonvasospastic women.

Adult↗
PubMed1997

Relationship between ocular pulse pressures and retinal vessel velocities.

PURPOSE: The authors quantified the relationship between ocular pulse pressures and retinal vessel velocities. METHOD: The blood velocity in the ophthalmic artery (OA), the central retinal vein (CRV), and artery (CRA) was measured by pulsed Doppler sonography (4-Mhz probe). The pulse curve of the intraocular pressure (IOP) was evaluated by pneumotonometry. With multichannel data acquisition and storage software, the velocity pulse curve of the OA, the CRV and CRA, the IOP-pulse curve, the arterial blood pressure, and the electrocardiogram were recorded simultaneously in real-time mode. The relationships between the pulse curves of the blood velocity in the OA, the CRV and CRA, and the IOP were calculated off-line. The onset time, the time of half maximum, and the time to the maximum of the pulse curves were evaluated. A relative retinal venous outflow resistance index (R') was calculated by R' = deltaIOP/deltaVcrv. We examined 23 eyes of 23 healthy subjects. The mean age of the group was 46 +/- 16 years. RESULTS: In all eyes, the outflow in the CRV was pulsatile and ran in synchrony with the IOP pulsation. The CRV velocity- and IOP-pulse curve showed a significant mean delay of 0.024 second compared with the CRA and OA velocity-pulse curve. The relative resistance index R' for venous outflow was 1.0 +/- 0.44 mmHg/cm/seconds. CONCLUSION: In all eyes, the authors found a significant linear relationship between the blood velocity in the CRV and the IOP pulsation. The CRV velocity- and IOP-pulse curve were significantly delayed compared with the CRA and OA velocity-pulse curve.

Adult↗
PubMed2004

Measurement of retinal vessel widths from fundus images based on 2-D modeling.

Changes in retinal vessel diameter are an important sign of diseases such as hypertension, arteriosclerosis and diabetes mellitus. Obtaining precise measurements of vascular widths is a critical and demanding process in automated retinal image analysis as the typical vessel is only a few pixels wide. This paper presents an algorithm to measure the vessel diameter to subpixel accuracy. The diameter measurement is based on a two-dimensional difference of Gaussian model, which is optimized to fit a two-dimensional intensity vessel segment. The performance of the method is evaluated against Brinchmann-Hansen's half height, Gregson's rectangular profile and Zhou's Gaussian model. Results from 100 sample profiles show that the presented algorithm is over 30% more precise than the compared techniques and is accurate to a third of a pixel.

Algorithms↗