Case Report: Cataract Surgery - The Horse Owner's Resource

Case Report: Cataract Surgery

Cataract surgery restores the vision of an Appaloosa gelding but complications threaten to plunge him back into blindness. By Patty Latham, DVM for EQUUS magazine.
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Cross-section of a horse's eye | Illustration by Celia Strain

Cross-section of a horse's eye | Illustration by Celia Strain

The statuesque white gelding lowered his head and snuffled my hand and the bucket that held my vaccines, swabs and a weight tape. Then he almost shrugged as if to say that all was well in his world.

As I prepared to administer the gelding's annual vaccinations, I paused to reflect on just how lucky he was. Two decades before, Go Native Go had come to his owner, Eva Iwicki, out of a gesture of gratitude.

Eva had bought a load of hay for a down-on-his-luck horse trainer near Palm Springs, Calif., and in return he gave her the then-3-year-old strawberry roan Appaloosa with a white blanket.

Eva planned to sell the young horse, but she kept him in training and even earned some Western pleasure ribbons with him. In between training and showing, Eva also began taking "GoGo" out on the trails.

Soon she found a buyer for GoGo, but before the sale was final, she had a change of heart. She just couldn't part with the gelding. Eva and GoGo continued to explore the high country of southern California, tracing the granite ridges of the Sierras on the Pacific Crest Trail from Running Springs to Big Bear.

GoGo was a steady, almost boring trail mount. He did seem to stumble a little more often than the average horse, and Eva noticed that sometimes he made bad decisions about which rock ledge to step on, but in general GoGo was an ideal trail horse.

Ten years and hundreds of miles of trail riding later, GoGo's occasional missteps took on new significance. Eva had just moved GoGo and another horse to her home farm and was handling them after dark for the first time when she noticed something odd about GoGo. The centers of his eyes were whitish, almost foggy.

She was concerned but hoped that this might be some harmless condition: After all, in the daylight GoGo's eyes looked perfectly normal, and he never acted as if they bothered him.

The next morning, Eva called in her veterinarian. She was stunned when a simple visual exam revealed that GoGo had extensive cataracts. He was blind.

The Diagnosis

Eva shipped GoGo to the San Luis Rey Equine Hospital near San Diego, where Alan MacMillan, DVM, PhD, an equine ophthalmologist, could examine him. MacMillan confirmed that GoGo had complete cataracts in both eyes and could discern only light and dark, no shapes or forms of any sort.

An opacity of the lens, cataracts affect an estimated 5 to 7 percent of horses. Most often, they are caused by equine recurrent uveitis (ERU), trauma or nutritional imbalances, but in some cases the tendency to develop the condition is inherited. Congenital cataracts, which may be present at birth or develop later in life, typically appear in both eyes at the same time. This seemed to be the most likely cause of GoGo's condition.

Fortunately, GoGo was a good candidate for cataract-removal surgery: He was in fine health, his cataracts had not completely hardened and his eyes showed no sign of inflammation.

In a procedure called phacofragmentation (also known as phacoemulsion), ultrasound waves are used to disrupt the crystal-like lens until it shatters, and the resulting fragments are removed via a catheter. Although no replacement lens is implanted as in similar surgery for human cataract patients, horses usually regain enough sight to function more or less normally after phacofragmentation.

Successful Surgery

Eva arranged for GoGo to have his cataracts removed at Texas A&M University, and he was admitted to the clinic in College Station on January 20, 1995. In the initial procedure, Joan Dziezyc, DVM, removed the gelding's right lens and a week later the left. (Because the surgery is done under general anesthesia, doing both eyes at once would have required that GoGo's head rest on a newly sutured eye during the second procedure.)

Both surgeries were successful and GoGo's recovery was uneventful. In fact, by the time the gelding was ready to go home a month later, he no longer needed any medication.

Back in his old pasture, GoGo acted like a horse half his age. And why not? As far as anyone knew, he was able to see his surroundings clearly for the first time in his life. The big gelding galloped around his field freely, bucking and kicking with zeal--he no longer had to be extra cautious about the footing or objects in his path.

Within a week, however, ominous signs of inflammation began to appear: GoGo's left eye was clamped nearly closed in a squint and was watering continuously. MacMillan prescribed a gel containing steroids and antibiotics, along with atropine to dilate the pupil and prevent the structures within the eye from forming adhesions and scar tissue. GoGo took it all in stride and seemed fine within a few days.

Complications Arise

Nine months later, Eva shipped GoGo to the San Diego equine hospital where MacMillan now practiced for a follow-up evaluation. Both of GoGo's eyes looked normal, but an examination with an ophthalmoscope revealed more trouble in the gelding's right eye.

He had developed a scar on the back of the lens capsule (posterior capsule sclerosis) and an adhesion of the lens capsule to the iris (posterior synechia). GoGo's pupil did not respond to light, nor did he have a blink reflex (menace response)--he didn't shut his eye if you jabbed a finger toward it. There was no doubt: GoGo could no longer see out of his right eye.

Also distressing were signs that the same conditions were developing in his left eye. Scar tissue also prevented this pupil from responding to light, but it had not yet completely blocked the optic nerve. GoGo was able to see, but just barely. What's more, the sclerosis would progress over time until he was once again completely blind.

GoGo had developed one of the worst possible complications of phacoemulsification surgery: uncontrollable, damaging inflammation.
Why this happened isn't clear, but an inherent weakness in the lens capsule may predispose it to tearing during or after surgery, which would set off the inflammatory process.

Nowadays, horses undergoing cataract surgery generally receive anti-inflammatory medications for at least two months after surgery, and in some cases the course of treatment is extended indefinitely as a preventive measure.

From Dark to Light

In the decade since his surgery, GoGo has readapted well to life without sight. He has shown no signs of pain or discomfort, and Eva continues to ride him.

Now aware of her horse's blindness, Eva recognizes his attempts to compensate, primarily through increased sensitivity to sound, smell and touch. Indeed, his responses to Eva's leg pressure would be the envy of any trainer.

A few years ago, Eva decided that GoGo needed a sighted companion for his "downtime" in the field, so she adopted Hobby, an aged Paint mare. Almost instantly, Hobby became part of the team. Eva rides GoGo and ponies Hobby on the trails. At home, Hobby is GoGo's "seeing eye" horse, sticking by his side as they roam the pasture.

Eva, her husband, GoGo and Hobby moved to Colorado about four years ago, and that's when I became one of GoGo's veterinarians. He is now 23 and Hobby is 29, and both are happy in their new home.

Today, GoGo is still traversing the safer trails of the San Juan National Forest, with Eva in the saddle and Hobby on a lead by his side ready to snort the occasional warning about obstacles ahead. The unlikely trio has developed an amazing partnership, relying on each other's senses and goodwill to function as a single unit. They have achieved a level of communication, connection and trust that the rest of us can only imagine.

This article originally appeared in the November 2005 issue of EQUUS magazine.