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PubMed2005

Automatic grading of retinal vessel caliber.

New clinical studies suggest that narrowing of the retinal blood vessels may be an early indicator of cardiovascular diseases. One measure to quantify the severity of retinal arteriolar narrowing is the arteriolar-to-venular diameter ratio (AVR). The manual computation of AVR is a tedious process involving repeated measurements of the diameters of all arterioles and venules in the retinal images by human graders. Consistency and reproducibility are concerns. To facilitate large-scale clinical use in the general population, it is essential to have a precise, efficient and automatic system to compute this AVR. This paper describes a new approach to obtain AVR. The starting points of vessels are detected using a matched Gaussian filter. The detected vessels are traced with the help of a combined Kalman filter and Gaussian filter. A modified Gaussian model that takes into account the central light reflection of arterioles is proposed to describe the vessel profile. The width of a vessel is obtained by data fitting. Experimental results indicate a 97.1% success rate in the identification of vessel starting points, and a 99.2% success rate in the tracking of retinal vessels. The accuracy of the AVR computation is well within the acceptable range of deviation among the human graders, with a mean relative AVR error of 4.4%. The system has interested clinical research groups worldwide and will be tested in clinical studies.

Algorithms↗
PubMed2006

Retinal vessel signs and 10-year incident age-related maculopathy: the Blue Mountains Eye Study.

OBJECTIVE: To examine whether retinal vessel signs are independent predictors of the long-term development of age-related maculopathy (ARM). DESIGN: Prospective population-based cohort study. PARTICIPANTS: Blue Mountains Eye Study participants aged > or =49 years (n = 3654) were examined during 1992 through 1994; 2335 (75% of survivors) were reexamined after 5 years and 1952 (76% of survivors) were reexamined after 10 years. METHODS: Baseline focal arteriolar narrowing and arteriovenous (AV) nicking were assessed and vessel calibers were measured from retinal photographs. A side-by-side grading method was used to assess ARM incidence. Eye-specific data were analyzed using generalized estimating equation models, adjusting for age, gender, smoking, and blood pressure. MAIN OUTCOME MEASURES: Incident early ARM (soft indistinct or reticular drusen or combined soft distinct drusen and retinal pigment abnormality) was defined in eyes free of both early and late ARM at baseline. Incident late ARM (either geographic atrophy or neovascular macular degeneration) was defined in eyes free of these 2 lesions at baseline. RESULTS: Over a 10-year period, incident late ARM developed in 106/4745 eyes at risk of late ARM (2.2%). Eyes with mild (2.7%) or severe (4.6 %) AV nicking were more likely to develop late ARM than eyes without this sign (1.5%). The adjusted odds ratio (OR) was 1.4, 95% confidence interval (CI) 0.8 to 2.4 for mild and OR 2.6, 95% CI 1.2 to 5.5 for severe AV nicking. Eyes with focal narrowing were also more likely to develop late ARM (7.6% vs. 1.8%), adjusted OR 2.2, 95% CI 1.1 to 4.1. Incident early ARM developed in 398/4490 eyes at risk of early ARM (8.9%). Severe AV nicking, but not focal arteriolar narrowing, was associated with an increased long-term risk of early ARM (13.6% vs. 8.2%; OR 1.5; 95% CI 1.0-2.3). Neither arteriolar nor venular caliber was significantly associated with the incidence of either early or late ARM. CONCLUSIONS: These 10-year incidence data confirm our previous observation that structural retinal arteriolar changes may either contribute to ARM progression or share common pathologic pathways with ARM, independent of traditional vascular risk factors.

Aged↗
PubMed1998

A novel mechanism for vasoconstrictor action of 8-isoprostaglandin F2 alpha on retinal vessels.

Using a video-imaging technique, we characterized the effects of 8-isoprostaglandin F2 alpha (8-iso-PGF2 alpha) on retinal vasculature from piglets. 8-Iso-PGF2 alpha potently contracted (EC50 = 5.9 +/- 0.5 nM) retinal vessels. These effects were completely antagonized by the cyclooxygenase inhibitor indomethacin, the thromboxane synthase blocker CGS-12970, the thromboxane receptor antagonist L-670596, and the putative inhibitor of the non-voltage-dependent receptor-operated Ca2+ pathway SKF-96365; constrictor effects of 8-iso-PGF2 alpha were also partly attenuated by the ETA-receptor blocker BQ-123 and an inhibitor of endothelin-converting enzyme, phosphoramidon, but was negligibly affected by the L-type voltage-gated Ca2+ channel blocker nifedipine. Correspondingly, 8-iso-PGF2 alpha elicited endothelin release from retinal preparations, which was markedly reduced by SKF-96365. 8-Iso-PGF2 alpha also increased thromboxane production in the retina and cultured endothelial cells, but not on retinovascular smooth muscle cells; these effects of 8-iso-PGF2 alpha were blocked by indomethacin, CGS-12970, SKF-96365, and EGTA, but not by nifedipine. 8-Iso-PGF2 alpha also increased Ca2+ transients in retinal endothelial cells, which were inhibited by SKF-96365 and EGTA, but not by nifedipine, whereas in smooth muscle cells U-46619, but not 8-iso-PGF2 alpha, stimulated a rise in Ca2+ transients. Finally, H2O2 + FeCl2 (in vitro) and anoxia followed by reoxygenation (in vivo) stimulated formation of 8-iso-PGF2 alpha in the retina. In conclusion, 8-iso-PGF2 alpha-induced retinal vasoconstriction is mediated by cyclooxygenase-generated formation of thromboxane and, to a lesser extent, by endothelin after Ca2+ entry into cells, possibly through receptor-operated channels. Retinal vasoconstriction to 8-isoprostanes might play a role in the genesis of ischemic retinopathies.

Animals↗
PubMed1977

[Treatment and follow-up of retinal tears associated with avulsed overlying retinal vessels (author's transl)].

The present clinical study is based on 17 cases of a specific clinical entity, which is characterised by a retinal break without retinal detachment, the tear being spanned by an avulsed patient retinal vessel invariably adjoining the operculum. The vessel was in the vitreous cavity and formed an arch above the break. All cases began with a sudden decrease or loss of visual acuity due to the rupture of the avulsed vessel and the occurrence of hemorrhages within the vitreous. These hemorrhages recurred in the course of the follow-up of the patients which lasted from 1-8 years. The recurrence of the bleeding was in most instances related to the mobility and the size of the vessel overlying the break. During treatment the cases were divided into two groups, group 1 comprising cases which were subjected only to light-coagulation, whereas in the cases of group 2 scleral buckling was performed in conjunction with cryopexy or light-coagulation. The comparatively best results were achieved in group 2. This condition is rare and amounted to only 1.5% of our total number of cases of retinal tears treated with light-coagulation during the last 8 years.

Aged↗
PubMed1978

Laser Doppler measurements of blood velocity in human retinal vessels.

We have measured Doppler shift frequency spectra (DSFS) of laser light scattered from red blood cells (RBC's) flowing through individual human retinal vessels. Each spectrum exhibits a cutoff frequency which is directly related to the maximum RBC velocity at the measurement site. Meaningful DSFS can be measured in times as short as 0.1 s. DSFS obtained from suspensions of polystyrene spheres and RBC's flowing through glass capillary tubes are used to illustrate the basic principles of the technique and to aid in the interpretation of the in vivo measurements. Our measurements show that maximum RBC velocities in retinal arteries vary markedly during each cardiac cycle.

Blood Flow Velocity↗
PubMedDate not supplied

Blood pressure effects on retinal vessel diameter and flicker response: a 1.5-year follow-up.

PURPOSE: The study examined the influence of individual blood pressure changes overtime on retinal vessel diameter and the latter's response to flicker light. METHODS: The diameter of a retinal arterial and venous segment was measured continuously on-line with a Dynamic Vessel Analyzer in 20 patients twice (mean interval between examinations of 24 months). Eleven patients had no cardiovascular disease. Nine patients had arterial hypertension and were untreated at the time of the first measurement; at the time of the second measurement they were undergoing various antihypertensive therapies. Each test consisted of a 50-s baseline plus three 20-s periods of flicker stimulation followed by an 80-s period of observation. During the examinations the blood pressure was measured at 1-minute intervals. RESULTS: In the hypertension group changes in the mean arterial blood pressure (MAP) correlated significantly with changes in the arterial baseline diameter (y = -0.1 - 0.37x, r =0.74, p (increase) <0.03). A comparison of the two measurements showed no such relationship in the group of cardiovascularly healthy subjects. The venous baseline and the arterial and venous flicker response did not change significantly in either group between the two measurements and showed no relationship to blood pressure changes. CONCLUSIONS: In hypertensive subjects, long-term therapy-related changes in blood pressure induced a change in the arterial baseline by approximately +3.7 microm/-10 mmHg MAP. An influence of lowering MAP to the arterial flicker response could not be detected.

Antihypertensive Agents↗
PubMed2006

Are inflammatory factors related to retinal vessel caliber? The Beaver Dam Eye Study.

OBJECTIVE: To examine the relationship of systemic markers of inflammation, endothelial dysfunction, and serum folate level to retinal vessel diameter. METHODS: Cross-sectional analyses were completed for data from a random sample of 396 persons aged 50 to 86 years who underwent a baseline examination from 1988 to 1990. Standardized protocols for blood collection and measurement of markers were used. Diameters of arterioles and venules were measured from digitized photographs. Standard univariate and multivariate analyses were performed. RESULTS: While controlling for age, smoking status, diabetes status, serum high-density lipoprotein cholesterol, and hematocrit, wider retinal venular diameters were associated with higher serum high-sensitivity C-reactive protein, interleukin 6, and amyloid A levels. While controlling for age, systolic and diastolic blood pressure, smoking, serum high-density lipoprotein cholesterol level, and gout, smaller arteriolar diameters were associated with higher serum amyloid A and lower serum albumin and folate levels but not high-sensitivity C-reactive protein or interleukin 6 levels. Levels of serum soluble intercellular adhesion molecule-1 and serum soluble E-selectin, markers of endothelial dysfunction, were not associated with retinal arteriolar or venular diameters. CONCLUSIONS: These data show an association of inflammatory markers with larger retinal venular diameter, suggesting that retinal venular caliber may be a marker of systemic inflammation.

Aged↗
PubMed1995

Strict control of glycaemia: effects on blood flow in the large retinal vessels and in the macular microcirculation.

AIMS: The purpose of this study was to investigate the effect of instituting strict diabetic glycaemic control on the retinal macular microcirculation and to compare this effect with that observed in the main retinal veins. METHODS: In 28 insulin dependent diabetic patients with poor glycaemic control a regimen of strict diabetic control, consisting of four daily insulin injections was instituted and maintained for 6 months. Retinal haemodynamics were investigated in the macular microcirculation by the blue field simulation technique and in the major retinal veins by a combination of bidirectional laser Doppler velocimetry and monochromatic fundus photography. Progression of diabetic retinopathy was assessed from fundus photographs taken at baseline and at the end of the study. RESULTS: Institution of strict diabetic control resulted in a significant increase in leucocyte velocity in the macular circulation (p = 0.013). No significant difference in this increase was observed between eyes that showed progression (n = 8) and no progression (n = 20) of retinopathy during the study. Significant correlations were found between relative changes over time of blood flow measured in the main retinal veins and relative changes of leucocyte velocity determined in the macular microcirculation at 2 months (p = 0.008) and 6 months (p = 0.001) but not at 5 days (p = 0.49). In the eight eyes that showed progression of retinopathy, the product of leucocyte velocity and density at baseline was significantly higher than normal (p < 0.05). During the length of this study, this product was also significantly higher in the eight eyes that showed retinopathy progression than in the 20 eyes that did not show progression (p = 0.005). CONCLUSION: Our results suggest that increased flow in the macular microcirculation may be associated with progression of retinopathy, thus supporting the hypothesis that increased blood flow may play a role in the development of diabetic microangiopathy. Although there are correlations between the changes detected in the macular microcirculation and those measured in the main retinal vessels, there are also differences which need to be further investigated in order to better understand pathogenetic mechanisms.

Adolescent↗
PubMed1992

Preservation of nerve fiber layer by retinal vessels in glaucoma.

The authors evaluated the correlation between various parameters and the local preservation of the retinal nerve fiber layer in 156 glaucomatous eyes. A vessel-associated preservation of the nerve fiber layer was observed in 45 of the 156 glaucomatous eyes. The presence of "straight" retinal vessels (either arterioles or large venules) and "tortuous" retinal vessels (large or small venules) inside of the scleral ring was correlated with the local preservation of the nerve fiber layer (P less than 0.001 and P less than 0.05, respectively). A local elevation of the floor of the cup was also correlated with the preservation of the nerve fiber layer (P less than 0.01). However, no correlation existed between either the preservation of the nerve fiber layer and the type of glaucoma, sex or age of patient, tilting of the disc, cilioretinal vessel, vertical cup-to-disc ratio, refractive error, disc size, distance between the disc and foveola, or the index of ovalness of the disc. These results suggest that retinal vessels in the disc significantly influence the vulnerability of the nerve fibers to glaucomatous damage.

Adult↗
PubMed1987

Effects of hyperbaric, normobaric and hypobaric oxygen supplementation on retinal vessels in newborn rats: a preliminary study.

An experimental study was conducted on eight litters of newborn rats to evaluate the effects of supplemental oxygen administration on the retinal vasculature. The animals and their mothers were kept inside a pressure chamber and treated for the first 5 days of life. On the sixth day, they were removed and kept for five more days under room air and normobaric conditions. Three litters received continuous flow oxygen at 80% at a compression pressure of +81 kPa, one litter oxygen at 80% at a pressure of -39.5 kPa atms and three other litters received oxygen at 80% under normobaric conditions. The eighth litter was treated with room air oxygen at a compression pressure of +81 kPa. A severe retinopathy with marked retinal neovascularization was seen only in the newborn animals of the litters that received oxygen supplementation under normobaric or hypobaric conditions. Retinal vessels showed no pathological changes in the litters treated with hyperbaric normoxia or hyperoxia. It is possible to hypothesize that the prolonged period of oxygen supplementation failed to produce harmful effects on the retinal vasculature because the moderate hyperbarism caused mild retinal and choroidal vasoconstriction thus preventing excessive oxygen transport to the inner retina from the choroid during hyperoxia without inducing structural damage to the retinal tissue.

Animals↗
PubMed1986

Isolation of the human T-cell leukemia/lymphotropic virus type III from aqueous humor in two patients with perivasculitis of the retinal vessels.

The human T-cell leukemia/lymphotropic virus type III (HTLV-III) has been isolated from aqueous humor in two patients with perivasculitis of the peripheral retinal vessels, an AIDS-related ocular manifestation. Both patients had antibodies to HTLV-III and although they presented with herpes zoster ophthalmicus, they did not present other symptoms known to be associated with HTLV-III infection. The isolation of HTLV-III from aqueous humor in these two patients with retinal perivasculitis suggests that the virus itself may play a role in the etiology of this ocular sign. The presence of infectious HTLV-III in the anterior chamber further emphasises the necessity to discard corneas from HTLV-III infected donors.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Cell replication in retinal vessels of streptozotocin diabetic mice.

The retinal vascular bed from streptozotocin diabetic mice was investigated with respect to cell replication. The diabetic animals showed a significantly decreased endothelial cell labelling index as compared to their normal controls. It is suggested that the low cell replication characterizes the early diabetic vascular disease and that this animal model may reflect the inducement of the simplex diabetic retinopathy.

Animals↗
PubMed1989

[A morphological study of the retinal vessels in experimental diabetic rats].

The retinal vascular network of experimental diabetic rats was studied by trypsin digestion 6 months after an elevation in blood sugar level to 400-600 mg/dl, when the retinal capillaries began to show pericyte loss, with appearance of capillary microaneurysms, acellular capillaries, venular obstruction, capillary varicosis and diametral irregularity. The possible mechanism of these changes were discussed.

Alloxan↗
PubMed1979

[Value and limit of photocoagulation for juxtafoveolar sub-retinal vessels (author's transl)].

Sub-retinal new vessels arising from the choroid are the most dangerous components in disciform maculopathies. The greatest advance made in their treatment has been due to the use of photocoagulation over the last few years, but their destruction by this method is still a very controversial subject. The aim of the present study was to define which lesions should be treated and which should not. Results demonstrated that the use of photocoagulation to destroy new vascular membrane which is very close to the foveola, is possible, and can restore vision or preserve useful visual acuity. The laser can be used very close to the centre of the foveola, even in a part of the central avascular area. A randomized study is now being conducted and should supply statistical evidence as to whether this treatment should or should not be recommanded.

Adult↗
PubMed2004

The age-dependent decrease in the myogenic response of retinal arterioles as studied with the Retinal Vessel Analyzer.

PURPOSE: To study the age-dependent change in myogenic response of retinal arterioles. METHODS: Fifty-one healthy volunteers with at least ten persons in each of the five age decades (I-V) between 20 and 69 years were subjected to diameter measurement of retinal arterioles using the Retinal Vessel Analyzer (RVA) during rest and during an increase in the systemic blood pressure when lifting hand weights. The transmural pressure in the retinal arterioles during the procedures was estimated from the blood pressure and the intraocular pressure and was compared to the accompanying diameter response. RESULTS: The retinal arteriolar diameter showed a significant decrease as a function of increasing weight for the two younger age groups below the age of 40 years (P=0.007, group I, and P=0.049, group II), compatible with perfect autoregulation, whereas no such change was observed in persons above this age (P=0.41, 0.053, 0.29 for groups III-V, respectively). CONCLUSION: Studies on autoregulation in retinal disease should consider the normal age-related decrease in diameter response of retinal arterioles when the blood pressure is changed.

Adult↗
PubMed1981

Retinal vessel photocoagulation: a quantitative comparison of argon and krypton laser.

Retinal arteries of owl monkeys were photocoagulated with single exposures to argon laser green light (514 nm), krypton laser green light (531 nm), and krypton laser yellow light (568 nm). The distribution of damage along the vessel in different retinal layers was characterized geometrically after serial sectioning of the histopathologic material. Krypton laser radiation (green and, to an even greater extent, yellow) produced measurably greater effects on retinal vessels and adjacent structures than on deeper retinal levels; argon laser radiation (green) produced greater effects on the pigment epithelium. Krypton yellow produced the greatest total effect. The location of damage to the retinal arteries and pigment epithelium differed, with the peak of the damage around the arteries being farther from the optic disc than was the peak of the pigment epithelial damage.

Animals↗