Comparison of angiographic dyes and injection techniques for ocular anterior segment angiography in horses

Abstract

OBJECTIVE To assess and compare 2 injection techniques for conducting ocular anterior segment indocyanine green angiography (ASICGA) and sodium fluorescein (SF) angiography in horses. ANIMALS 3 healthy adult female horses (age range, 19 to 25 years). PROCEDURES Horses were sedated, jugular catheters were placed, and manual restraint was used to ensure proper positioning for the angiography procedure. Two injection techniques (IV and intra-arterial) were performed for each horse 1 week apart. Intravenous injections of 0.25% indocyanine green (ICG; 50 mg) and 10% SF (10 mg/kg) were administered via the jugular catheter. Intra-arterial injections of ICG (1 mg) and SF (1 mg/kg) were administered into the common carotid artery with ultrasound guidance. Angiography was performed by use of an adaptor system comprised of a modified digital single-lens reflex camera, camera adaptor, and lens. Imaging was performed at a rate of 3 images/s for 60 seconds immediately following ICG injection, then at 2, 3, 4, and 5 minutes after injection. The SF was injected 5 minutes thereafter. RESULTS ASICGA allowed visual identification of the arterial, capillary, and venous phases of angiography. Intra-arterial administration provided superior dye fluorescence, sharper contrast, and faster dye passage than IV administration. Visibility of the iris vasculature was limited with SF, and extravasation of SF was noted. No clinically important adverse events were detected. CONCLUSIONS AND CLINICAL RELEVANCE ASICGA images were obtainable with both injection techniques; however, visibility of the iris vasculature was better with intra-arterial administration of ICG. The ASICGA technique may serve as a viable ocular imaging modality for horses.

Clinical utility, dose determination, and safety of ocular contrast‐enhanced ultrasonography in horses: A pilot study

“…The implementation of conventional delivery contrast imaging in large animals, whose blood volume is many times more than in other species, is challenging. Pirie et al compared intravenous and intra‐arterial ICG and SF for anterior segment angiography and recognized a significant effect of dilution after intravenous injection before ocular vascular is reached. Their study population comprised only three horses but no drawbacks other than mild hemorrhage and minimal additional time were reported with ultrasonographically guided temporary common carotid artery catheterization .…”

“…Pirie et al compared intravenous and intra‐arterial ICG and SF for anterior segment angiography and recognized a significant effect of dilution after intravenous injection before ocular vascular is reached. Their study population comprised only three horses but no drawbacks other than mild hemorrhage and minimal additional time were reported with ultrasonographically guided temporary common carotid artery catheterization . The results of previous research proved superior contrast enhancement after intra‐arterial microbubble or dye administration which warrants further investigation of this route for ocular CEUS in horses.…”

“…Their study population comprised only three horses but no drawbacks other than mild hemorrhage and minimal additional time were reported with ultrasonographically guided temporary common carotid artery catheterization . The results of previous research proved superior contrast enhancement after intra‐arterial microbubble or dye administration which warrants further investigation of this route for ocular CEUS in horses. A rapid wash‐in and a stronger contrast enhancement are expected leading to a higher diagnostic utility.…”

“…Especially in uveal hemangiosarcoma and lymphoma diagnosis from clinical appearance can be challenging. Anterior segment angiography in horses using indocyanine green (ICG) and sodium fluorescein (SF) failed to visualize the major iridal arterial circle, and SF enhancement was compromised by ocular pigment and dye extravasation …”

“…Blood flow and microvasculature alterations occur inherently with different types and stages of canine uveitis . It is unknown whether contrast‐enhanced qualitative or quantitative assessment of uveal perfusion might facilitate ERU diagnosis and monitoring …”