CASE REPORT

Prompt veterinary attention and a thoughtful treatment plan save the vision of a stallion with a dramatic-looking eye injury.

Looking good: Prompt veterinary attention and a thoughtful treatment plan save the vision of a stallion with a dramatic-looking eye injury.

Spark’s right eye was not a pretty sight. The 7-year-old Quarter Horse stallion had tangled with something in his paddock ---no one was certain what---and he arrived at the University of Saskatchewan’s veterinary clinic late Saturday evening with a large laceration on his right foreleg and a gruesome-looking eye: The entire globe was cloudy, and a small piece of brown tissue from the interior was projecting out through the surface.

However, veterinary ophthalmologist Lynne Sandmeyer, DVM, was guardedly optimistic when she first met and examined Spark. “His eye did look alarming,” she says, “and his owners were understandably very worried. But they had brought him in immediately, which increased his chances of a good outcome.”

After a general physical exam, which showed Spark to be healthy apart from his injuries, the veterinary team tended to the laceration on the stallion’s foreleg first. Although the wound was large, it hadn’t affected any tendons or joints, and the horse wasn’t significantly lame.

“He didn’t need any sutures, but we did clean and debride the wound thoroughly,” says Sandmeyer. “We also applied a bandage that he’d need for the next few days.”

Then the team turned their attention to Spark’s eye. “Looking just with a penlight, we could see there was a clean, full-thickness laceration on his cornea, the outer surface of the eyeball,” says Sandmeyer. “It was the type of cut that’s made from something very sharp, like a wire.” She also noted that the brown tissue projecting from the laceration was a piece of the horse’s iris---the pigmented structure within the eye that controls the size of the pupil by constricting and expanding.

But as shocking as it looked, the fact that Spark’s iris was projecting out through the front of his eye wasn’t unusual---and it could even be considered a good thing.

“As soon as a horse sustains a full-thickness cut through the cornea, aqueous fluid within the eye begins rushing out, causing an immediate drop in pressure,” says Sandmeyer. “As the pressure drops, things are sucked out through the wound. The iris, which normally sits in front of the lens, gets pulled forward into the laceration. This ends up ‘plugging’ the leak, as it were, and actually works to stop the fluid loss.”

Trauma to the eye also triggers an influx of inflammatory-related substances, one of which is the sticky protein called fibrin. “Fibrin collects around the laceration and the displaced iris to form a tight seal around the wound,” says Sandmeyer. “This all happens in a few minutes after such an injury and is a pretty effective way of dealing with the immediate problem of aqueous fluid loss.”

Sandmeyer continued the ocular exam. She saw no response to the “menace” test, meaning Sparks didn’t reflexively blink or attempt to avoid a hand coming toward his eye. This suggested that he wasn’t seeing clearly, if at all, out of his right eye.

“His lack of vision could have been due to a few things,” says Sandmeyer. “For starters, his eye was cloudy. Normally, the fluid in the eye is crystal clear, but when proteins accumulate

with inflammation, that fluid starts to become cloudy, and the horse simply can’t see through it.”

Other possibilities included a damaged lens or retina. In a healthy eye, these internal structures can be seen with a tool called a slit lamp, essentially a hand-held microscope with a light source. But the cloudiness in Spark’s eye made it impossible for Sandmeyer to see these structures: “We’d decided to get the inflammation under control and reassess him Monday morning.”