Fluorangiographic study of the ocular fundus in normal horses.

The research article describes a study that used fluorescein angiography (FA) to examine and map vascular flow patterns in the eyes of healthy horses. The authors identified two main angiographic phases and three stages within the second phase, hoping that this procedure may be a useful tool for studying the health of the horse’s eye blood vessels.

Methodology

For the study, the researchers used a total of 25 healthy horses aged between 5 and 15 years. The horses were first sedated using a combination of detomidine and butorphanol. As part of the preparation, the horse’s eyes were also dilated using a topical solution named tropicamide.

• An angiogram, or an image of blood vessels, was taken by injecting the horse with a bolus intravenous dose of a fluorescein sodium solution. This fluorescent dye allowed observation of blood flow through the vessels in the eye.

Results

The fluorescein dye in the blood highlighted two major phases in the ocular blood flow:

• The choriopapillary phase, which started around 46.95 seconds
• The retinal vascular phase, starting around 47.79 seconds

The latter was further divided into three parts:

• Filling phase, wherein the dye was observed to progress into the retinal vessels
• Maximum fluorescence point, which occurred at approximately 59.79 seconds and represented the highest level of vascular filling
• Fading phase, which started immediately following the maximum fluorescence point and during which vascular fluorescence decreased to complete reduction, averaging around 74.76 seconds in total

In the process, the researchers also recorded features such as areas of delayed choroidal filling, the presence of short retinal vessels in the ventral region of the optic disc, and particularities in the filling of the optic disc.

Conclusion

This research successfully outlines the normal angiographic sequence in horses using FA. The technique allows for direct visualization and mapping of ocular vascular flow. The authors hence propose that FA might be beneficial in evaluating the health and integrity of blood-retinal barriers in horses, providing a diagnostic tool for eye-related pathologies in these animals.