Evaluating Retinal Circulation Using Video Fluorescein Angiography in Control and Diabetic Rats

Abstract

Video fluorescein angiography has been used to evaluate retinal circulatory parameters in diabetic and non-diabetic Sprague-Dawley rats. Video fluorescein angiograms were recorded from the retina using a modified retinal fundus camera following a 5 ul bolus injection of sodium fluorescein dye into the jugular vein. Retinal circulatory parameters were measured using computer assisted image analysis. These analyses were performed on 25 diabetic rats with 1 week duration of diabetes and 26 matched, non-diabetic, rats. There was a significant (p = .0001) increase in retinal Mean Circulation Time (MCT) in the diabetic group (1.83 +/- 0.40 s) compared to the control group (1.09 +/- 0.27 s). There were no significant differences in arterial or venous diameters comparing diabetic and control groups. In a separate paired experiment, measurements were made from the same animals both before and after one week duration of diabetes. A paired t-test analysis demonstrated significantly increased MCT times in the 6 diabetic animals (p = .001) while there was no significant differences detected in the 4 corresponding control animals. These results indicate that significant increases in retinal circulation times can be measured as early as 1 week after streptozotocin induced diabetes in this animal model.

Angiotensin AT 1 receptor antagonism normalizes retinal blood flow and acetylcholine-induced vasodiliation in normotensive diabetic rats

“…The video fluorescein angiography (VFA) system used for these studies has been described previously [11,18,19]. Briefly, the system consists of an imaging camera, a video digitizing system, and an archival unit.…”

“…All animals, 24 h before retinal blood flow measurements, (under anaesthesia, 50 mg/kg pentobarbital sodium; Abbott Laboratories, North Chicago, Ill., USA) underwent catheterization with a polyvinyl catheter inserted into the right jugular vein as previously described [11,18,19]. The catheter was flushed with 0.1 ml of 1000 U sodium heparin before and after implantation.…”

“…The rats were positioned on a platform attached to the imaging camera. The optic disc was centred and focused in the field of view, the VFA recording sequence was initiated, and a 5 µl bolus of fluorescein dye was rapidly injected into the jugular vein catheter [11,18,19]. The injection time was marked on the video recording.…”

“…Intravitreal injections were carried out by inserting a 27-gauge needle, attached to a 10 µl syringe (Hamilton), into the vitreous from a site 1 mm posterior to the limbus, as previously described [11,18,19,20]. Injections were carried out directly over the optic disc region under direct visualization, and a timer was immediately started.…”

“…This haemodynamic change has been described in patients with Type 1 diabetes [8,9,10] and in rodent models of diabetes [11]. The decrease in RBF caused by diabetes occurs prior to the development of histological abnormalities and is the result of increased microvascular resistance, which reduces the velocity of blood perfusion across the retinal arterioles and capillaries [9,11].…”