Superior Temporal Vein Research Articles

Retinal vasodilation and hyperglycaemia in diabetic children and adolescents.

Retinal vessel diameters of 45 diabetic children and adolescents with diabetes were measured on black-and-white fundus photographs (negatives) using digital image analyses technique and microdensitometry as well as with direct micrometry. The changes in vessel diameters in two sets of photographs taken at an interval of 2.4 +/- 0.3 years were compared with glycated haemoglobin level, retinopathy status and various other parameters. During the follow-up period both arterial and venous diameters increased significantly (p = 0.0436 and p = 0.0001, respectively), but the changes in individual vessels and between patients differed markedly. The superior temporal vein dilated more than the inferior temporal vein. The average increase in venous calibre was related to the glycated haemoglobin level on the date of the second examination (p = 0.0492). Signs of early retinopathy developed more often in the eyes with venous dilation (6 of 18 eyes) than in those without (3 of 24 eyes), but the difference did not reach statistical significance. The results indicate that retinal vasodilation is associated with chronically elevated blood glucose level in diabetic children, and may precede development of other signs of retinopathy.

Retinal vessel autoregulation in sickle cell patients.

We tested retinal vessel autoregulation in 16 sickle cell patients and 6 controls by computer-assisted measurements of constriction of the superior and inferior temporal veins and arteries after pure oxygen breathing. Compared to the controls and corrected for age, we found a decrease of vasoconstriction in three of the four vessels measured in the sickle cell group, which was statistically significant only for the superior temporal artery (P 0.009). The number of patients was too small to allow a separate analysis of possible contributory factors within the sickle cell group, such as sickle cell hemoglobin subtype and extent of retinal ischemia. Our findings indicate a factor not yet well known in the pathophysiology of sickle cell disease: an abnormality of local microvascular control.

Reproducible estimation of retinal vessel width by computerized microdensitometry

An objective method for reliably estimating the width of retinal vessels is presented. A computerized microdensitometer scans film negatives of fundus photographs and reconstructs black and white images of the fundus on a visual display terminal. After this initial scan, a desired region of a retinal vessel is selected with moveable cursors, and a cross-sectional density profile through the vessel is plotted. Vessel width is determined by the half-height width of the profile of the minimum (least transmitting) and average background film densities. Measurement sites can be accurately reproduced on different negatives by landmark mapping. A series of ten fundus photographs were taken of three healthy human eyes, and the width of the superior temporal vein was measured in two places on alle negatives. The coefficient of variation of the six sets ranged from 1.2 and 3.4% with an average of 2.2%.

Estimation of retinal blood flow by measurement of the mean circulation time.

A method is described for measuring the segmental mean circulation time and estimating the segmental flow in the human retina. Serial retinal photographs were taken after intravenous fluorescein injection and the relative concentration of fluorescein in the superior temporal artery and vein calculated from measurements of the optical density of the vessel images. Arterial and venous time-concentration curves were constructed and the mean circulation time calculated. In normal subjects the mean circulation time in the superior temporal segment varied from 1·39 to 6·85 sec. This variation was largely explained by variations in the volume of the vascular bed which was taken to be related to the sum of the square of the arterial and venous diameters. Volume flow showed less than a two-fold variation in normal subjects, mean 55 ± SD 11 units/sec. Similar results for volume flow were found in hypertensive subjects, although flow was more variable in these patients, mean 54 ± SD 18 units/sec. Some anaemic patients showed a marked increase in volume flow, and there was a significant relationship between packed cell volume and retinal volume flow (R = 0·65, P = 0·01).