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Every horse owner has a once-in-a-lifetime horse. Mine is Kannon, a 16-year-old Hanoverian gelding I bought as a two-year-old. This horse has loved his job from day one, and he’s carried me more miles and won more blue ribbons than all my other horses put together. 

Two summers ago, as I was bringing him into the barn from his paddock, I noticed his left eye was half shut and tearing excessively. I wasn’t immediately concerned—he had probably just scratched it while grazing in a patch of deep grass, or maybe he had gotten some dirt or debris lodged under his eyelid. But when the squinting and tearing worsened the next day and Kannon appeared to be in serious pain, I called my veterinarian. 

When the vet diagnosed Kannon with moon blindness, or equine recurrent uveitis, I was equally stunned and devastated. In my work with rescue horses, I’ve seen several horses with moon blindness, and most of them were elderly and had been, at some point, poorly cared for or even neglected. And even more terrifying, they were all blind, in one or both eyes. Before my own horse was diagnosed with this terrible eye condition, I had the impression that it only affected horses that didn’t receive proper management or care. I was wrong. 

As it turns out, moon blindness is the most common cause of blindness in horses. It’s hard to know how common it is, because many horses will never be diagnosed or treated, but it’s believed to affect up to 25 percent of horses worldwide, regardless of how well they are loved and cared for. More than half of affected horses will end up blind, and more than 60 percent will never return to their previous level of work, competition, or even play. Sadly, many of these horses will be euthanized. 

Equine recurrent uveitis is characterized by repeated episodes of inflammation of the middle layer of the eye, called the uvea, and it can involve one or both eyes. Over time, and with repeated episodes, the damage can lead to blindness. 

The root cause of equine recurrent uveitis isn’t clear cut. In some cases, infection with the bacteria Leptospira has been associated with moon blindness, and treatment often involves administering antibiotics, which might be injected into a vein or into the eye itself. But even in horses testing positive for Leptospira, administering the appropriate antibiotics doesn’t always work, and the disease continues to progress and worsen. There’s also strong evidence to suggest that with or without Leptospirosis as a trigger, moon blindness is the result of a complex autoimmune process, in which the body’s natural defense mechanisms don’t distinguish between its own tissues and foreign invaders, leading the cells of the immune system to mistakenly wage war on the body, releasing damaging toxins and attacking and destroying vital tissues. The end result, in the case of moon blindness, is significant inflammation in the eye, and it is the inflammation that contributes to the pain and structural damage to the eye. 









Genetic factors also appear to play a role in equine recurrent uveitis. Appaloosa horses, for instance, are particularly susceptible. Studies suggest that Appaloosas are eight times more likely to develop the condition than other breeds, and these horses are significantly more likely to suffer blindness in one or both eyes. Other at-risk breeds include American Quarter Horses, Thoroughbreds, American Paint Horses, and Warmbloods, including Hanoverians like my horse Kannon.

Before I knew how serious moon blindness is, I assumed that when my veterinarian treated the condition, Kannon would bounce back to normal, just as he had when we treated hoof abscesses or muscle strains. To be fair, the vet warned me that treatment would be expensive and time-consuming, with repeated collection of blood samples, daily injections of antibiotics, steroids and analgesics, oral pastes, and four-times-a-day eye drops and ointments. It would also be necessary to confine Kannon to a dark stall during daylight hours for at least a couple of weeks. I didn’t mind the extra work or expense, because in the end, Kannon would be cured, right? Wrong again. After several weeks of treatment and no appreciable improvement, my vet gently broke the news to me. Kannon wasn’t responding to the medicines. His condition was, in fact, getting worse. While treatment sometimes results in improvement, my vet told me, veterinary medicine has no definitive cure for equine recurrent uveitis. With nothing left to offer, he referred us to an equine ophthalmologist. 









After examining Kannon’s eye, the veterinary ophthalmologist confirmed the diagnosis of equine recurrent uveitis and told me that there were a few additional treatment options. Again, these would be time-consuming and even more expensive, and she wasn’t optimistic that they would be any more effective. And they weren’t. Kannon was losing sight in his left eye. And he was in tremendous pain. It was getting harder and harder to give the medicines—it’s not an easy thing to administer eye drops to a 17 hh horse while he’s pulling his head away and squeezing his eyelids shut, which incidentally, are powered by some of the strongest muscles in the horse’s body. And who could blame him? His eye was hurting, and he didn’t want anyone touching it. I knew that the combination of unrelenting pain, steroids, antibiotics, and anti-inflammatory drugs was putting him at high risk for stress-induced laminitis or gastric ulcers. I started him on even more medications as a precaution against these conditions. 

After several more weeks of treatment and no discernable improvement, the ophthalmologist suggested that I consider taking the next step. One option was surgically implanting a pellet that would continually release an immune-suppressing drug into the eye. This procedure might help quiet the over-reactive immune system, preventing it from attacking the eye, but there was no guarantee of a cure. If it did help, the implant would have to be replaced every three years or so. The other option was surgically removing the diseased eye. Both made my heart hurt. I didn’t want to put my horse through any more pain and suffering. Surely there was some other, less invasive way to keep Kannon out of pain and save his eye, if not his sight. The ophthalmologist was sympathetic, but she had nothing else to offer.

I shared my grief and frustration with my farrier, who is without a doubt one of the most knowledgeable horse people I know. He went to his truck and came back with a container of Serraquin ES15. Just mix two scoops of this in his feed twice a day for the first two weeks, then you can go to one scoop twice a day, he told me. His eye will clear up in a couple of days. He said like it was no big deal—just an undisputable fact. Like my horse had a patch of ringworm or a mild case of thrush. I didn’t actually roll my eyes, but I was tempted. I was grateful for the effort, but at that point, I had absolutely zero confidence in his prediction. As smart and as experienced as my farrier was, he clearly didn’t understand the severity of my horse’s condition or the devastating process of this disease. Over the course of several months, I had spent thousands of dollars on the very best veterinary care and pharmaceuticals available, and he wanted me to believe that a supplement would help? And in a couple of days, no less?

I should mention here that in addition to being a horse person, I’m also a physician. I was trained to practice modern medicine, which whole-heartedly embraces the use of pharmaceutical drugs and surgical interventions. I’ve written thousands of prescriptions for medications over the years, and in many cases, those medications have saved or prolonged my patients’ lives. But early in my career as a physician, I developed an intense interest in holistic medicine, and I’ve spent years studying the application of natural remedies. When appropriate, and if a patient is interested, I routinely discuss alternatives to pharmaceuticals, including herbs, plant foods, nutritional supplements, and dietary changes as a therapeutic approach. I’ve seen dramatic improvements in many of my patients who opt for natural treatments. But whether I provide treatment with pharmaceuticals or holistic therapies, I have never seen a serious, progressive condition, just “clear up” in a couple of days. Especially an autoimmune-related disorder, like moon blindness.








Nonetheless, I thanked my wise and generous farrier for the gift of Serraquin ES15. And as soon as he drove off, I did roll my eyes. But there was no way I wasn’t going to try it. I was desperate to help my horse. When I studied the Serraquin ES15 label I realized that I was familiar with many of the ingredients—mostly enzymes. In all my years of practicing medicine, I have developed a tremendous respect for the power of enzymes. I’ve taken them myself and prescribed them to many of my patients, especially for the treatment of various inflammatory conditions. But because I am not trained as an ophthalmologist, I’ve rarely had the opportunity to treat patients with chronic inflammatory eye disease, and so it never occurred to me that—of course!—the healing power of enzymes would be of enormous benefit in the treatment of moon blindness, since inflammation is the very thing responsible for the destruction of the eye, and the associated pain. 

Inflammation plays a key role in moon blindness. 

As the tissues in the eye are destroyed, the resulting dead cells and debris begin to accumulate in the eye, perpetuating the cycle of inflammation and destruction, and of course pain. The enzymes in Serraquin ES15 not only help stop the process of inflammation, they also serve to clean up the site of injury. These enzymes break down and digest the cellular debris trapped inside the eye so that it can be carried away by the bloodstream. Because there is less inflammation, blood vessels are no longer squeezed shut, and they remain open to carry blood freely to and from the eye. Without the inflammation, healing nutrients can be more easily delivered to the eye, and toxins and cellular waste can be more easily carried away. Because enzymes also serve as powerful catalysts that ignite the body’s natural reactions, they speed up the processes of both waste removal and healing. 

I could have kicked myself for not thinking of using enzyme therapy for Kannon in the first place, if not as a stand-alone treatment for his condition, at least as a complement to the pharmaceutical drugs and the veterinary treatment. If I had remembered what I knew about the healing power of enzymes, I might have saved my horse a great deal of pain and suffering. I started Kannon on Serraquin ES15 immediately, and just as my farrier predicted, his eye was dramatically better in a couple of days. The discharge from his eye was completely gone by day two, and by day three he was no longer squinting. I had no way of knowing if his vision was improving, but I did know that after months of suffering, he was no longer in pain. It was like the whole terrible, heart-breaking experience never even happened. 

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I wish I could tell you how the story ends. I don’t know if Kannon’s moon blindness will remain in remission for the rest of his life, although I have now read accounts of horses on Serraquin ES15 remaining symptom free for years. Since I started him on Serraquin ES15 and stopped all the other medications and treatments a few months ago, Kannon hasn’t had a single bad day. His eye is wide open and bright, and he is pain free. I’m thankful for every good day we have, and I’ll keep Kannon on Serraquin ES15 for the rest of his life. 

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Kannon is now retired from competition, but he’s still working. His new job is to babysit and socialize the young horses, and he still loves being active and involved in the daily routine. As my once-in-a-lifetime horse, he will always have a home on my farm, and a one-of-a-kind place in my heart. 

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~ Rallie McAllister, MD, MPH