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

This research article explores the efficacy and safety of two types of dyes and injection techniques used in anterior segment angiography—an imaging procedure used to visualize the blood flow in the eyes—in horses. By using intravenous and intra-arterial injection techniques with two types of dyes, the study aims to determine which type offers better visibility and safety for veterinary use.

Research Methods

• The study utilized three healthy mature female horses, each aged between 19 to 25 years.
• All horses underwent two separate angiography procedures, namely anterior segment indocyanine green angiography (ASICGA) and sodium fluorescein (SF) angiography, conducted a week apart.
• The researchers injected the dyes—0.25% indocyanine green (ICG; 50 mg) and 10% SF (10 mg/kg)—into the horses’ veins via a catheter in the jugular. In addition, intra-arterial injections of ICG (1 mg) and SF (1 mg/kg) were carried out into the common carotid artery with ultrasound guidance. Both procedures took place while the horses were under sedation and manual restraint.
• For visualization of the blood flow, the researchers used a specialized adaptor system that includes a modified digital single-lens reflex camera and a camera adapter plus lens.
• Imaging was recorded at a rate of three images per second for 60 seconds right after ICG injection. Following this, images were taken after 2, 3, 4, and 5 minutes of the injection. The SF was injected after 5 minutes post the ICG injection.

Results

• Both methods allowed visual identification of the arterial, capillary, and venous phases of angiography. However, intra-arterial administration demonstrated superior dye fluorescence, sharper contrast, and faster dye passage than the intravenous administration.
• The study found that SF limited the visibility of the iris vasculature and also noted an extravasation (leakage) of SF.
• Crucially, no clinically significant adverse events were observed during the study, implying that both techniques are generally safe.

Conclusions and Clinical Relevance

• Overall, the study suggests that both injection techniques of ASICGA can provide ocular imaging for horses, but intra-arterial administration of ICG offers better visibility of the iris vasculature.
• The data therefore propose that the ASICGA technique can serve as a viable ocular imaging modality for horses in clinical practice, potentially helping veterinarians make more accurate diagnoses and treatment plans for ocular conditions.