my horse has glaucoma

I was working when the barn manager called around 8:30 in the morning on Memorial Day 2016 to tell me that ET’s right eye was swollen shut.

My 16-year-old Appendix gelding has a propensity for getting into trouble, so this wasn’t the first time I’d made an emergency call to the vet. I hurried to the barn and met Dr. Cathe Montesano, of Montesano and Tallarico, DVM, LLP, in Smithtown, New York. After an examination, however, she gave me the most serious eye-related diagnosis I’d received: “ET has glaucoma.”

Come again? He was fine yesterday. How did this happen?

What is Glaucoma?

The Merck Veterinary Manual defines glaucoma as a group of diseases characterized by increased intraocular pressure with resultant retinal and optic disk destruction—basically, increased pressure within the eye that can cause vision-threatening damage. Glaucoma can be painful, potentially chronic and difficult to treat. Elevated intraocular pressure can impede blood flow to the retina and damage to the optic nerve, causing damage and potentially blindness.

Glaucoma can result from a chronic inflammatory condition, such as uveitis. But because ET has never had uveitis, the veterinarians ruled it out as a cause. ET did have a small corneal ulcer, however, suggesting he had poked his eye. This made board-certified veterinary ophthalmologist Dr. Noelle La Croix of the Veterinary Medical Center of Long Island (VMCLI), in West Islip, New York, think ET likely had “ocular hypertension,” similar but a bit different than true glaucoma.

“ET’s eye was traumatized, and the pressures in this eye were elevated,” she clarified. “All eyes that have had trauma or inflammation are at risk for glaucoma in the future.”

Dr. Montesano and her husband and partner, Dr. Nick Tallarico, completed the initial eye exam on both eyes. The pressure in the injured eye was about 44 mmHg; normal intraocular pressure is somewhere between 23-28 mmHg. One concern with high intraocular pressure is damage to the retina, on which the horse depends for good focus and clear vision. As such, we needed to get ET’s eye pressure down ASAP. Unfortunately, ET’s eye had so much pressure that Dr. Montesano couldn’t immediately determine whether his retina was damaged.

Another side effect—and, ultimately, potential complication—of the high intraocular pressure is a dilated pupil. ET’s pupil left very little of his iris visible, but the veterinarians could see fibrous striations (strands of fiber within the eye) that resulted from the inflammation. If the fibers didn’t break up, they could impair his vision. Treatment commenced immediately, with antibiotic ophthalmic ointment three times per day, two drops dorzolamide in the eye four times per day to decrease aqueous humor (the fluid that fills the eye) production, and oral flunixin meglumine to control pain and inflammation two times per day.

Day 2, May 31 Drs. Montesano and Tallarico came to check ET at the end of their long day (fortunately they live close by!) I had my truck and trailer ready to go in case we had to make an emergency trip to the referral hospital. Good news! The intraocular pressure in ET’s injured eye had decreased, and his retina appeared to be healthy. But the eye was still inflamed and the fibrins were still there. The veterinarians instructed me to continue treatment, and they’d stop by in three days for a recheck. They also recommended I make an appointment Dr. LaCroix.

June 11 We had our first visit with Dr. La Croix. She confirmed a healthy retina and that the dorzolamide had normalized the eye pressure. The small corneal ulcer had healed, and the ointment was no longer necessary. All good news! However, she discovered a vitreous prolapse.

“Vitreous prolapse is when the ‘jelly’ that is normally present between the lens and the retina slips around the lens and enters the anterior chamber,” she explained.

Dr. La Croix advised continuing one drop of dorzolamide three times per day but stopping the flunixin meglumine. She also gave permission for some light riding. ET’s vision did not seem impaired, but his pupil had still not returned to its normal size. So, he needed to wear a fly mask for shade during turnout and riding. We would have a follow-up appointment at the clinic in two to three weeks.

June 30 We set off to see Dr. La Croix again, who found that ET’s eye pressure was below normal, meaning we could stop the drops. But, she noticed that a small cataract had developed, likely secondary to oxidative stress, she said. We scheduled another follow-up for two weeks later, at which point all medication would be stopped. I was still holding my breath.

July 15 It was almost 90 degrees and humid on Long Island that day. Fortunately, my trailer stays relatively cool, and we made it to the clinic safe and sound. I relayed an observation to Dr. La Croix—that conventional wisdom usually doesn’t apply to ET, and things that are normal for other horses usually aren’t normal for him.

“Well, talk about conventional wisdom,” she replied. “That vitreous prolapse is gone.”

I was ecstatic!

ET’s eye pressure was stable, and his pupil had returned to normal, but the cataract remained. While ET charmed the technicians at VMCLI, I fired off a million questions to Dr. La Croix. Is the cataract going to get worse? Will he need surgery? Will it affect his vision? Do I need to worry about it?

To my relief, she answered “no” to each inquiry. I wanted to hug her. Still, she said, “I want to see ET in six months.”

January 2, 2017: Six-month follow-up with Dr. LaCroix.

ET’s eye pressure remained normal and stable in both eyes, with no change in the small cataract in the right eye. However, a small vitreous prolapse had returned.

“In ET’s case, the prolapse has come and gone,” La Croix said. “Most likely the prolapse is a result of breakdown of the attachments to the lens secondary to the original trauma.”

She didn’t seem worried but asked, “Can I see ET again in a year?” Of course! I asked if she was sure she didn’t want to see him sooner, but we’ll come back next January. It’s a condition I am always going to have to watch for. Every day at the barn, I’ve made it a habit to check ET’s eyes. I look for any changes, tearing or swelling, and I check his pupils as best I can. If I see anything unusual for him, I have the veterinary team on speed dial.

The condition is chronic in most horses. As Dr. LaCroix diagnosed ET with intraocular hypertension, as opposed to true glaucoma, we dodged a bullet here, but nonetheless he’s at risk for future problems in the affected eye and I must remain vigilant.

A Lyme Connection?

I’m fortunate that, to date, ET’s condition has healed well. I am also fortunate that he was insured, because the vet bills approached $4,000.

I’d be remiss not to mention that at the start of all this, Dr. Montesano suggested testing ET for Lyme disease. While I knew he’d been bitten by ticks in the past, I hadn’t seen any recently. That’s not to say the ticks weren’t there or that the virus hadn’t been latent, but we live on Long Island, New York, after all—a high-risk area for Lyme disease. Sure enough, ET was a strong positive (with both the SNAP test and Western blot analysis).

Could there be a link between the two?

“The link in horses is less clear,” Dr. La Croix said. “We don’t have a lot of research dollars in animal medicine.”

Dr. Montesano added, “Lyme disease can cause uveitis. Once a horse has had two bouts of uveitis, they’re considered recurrent cases. Recurrent uveitis leads to damage in of the uvea, making it more prone to inflammation.”

Take-Home Message

One of my graduate school mentors, Dr. Michael Fugaro (Dipl. ACVS) of Mountain Pointe Equine Veterinary Services, in Hackettstown, New Jersey, said to me years ago, “Eye injuries are always an emergency.”

Being a lifelong horse person, I knew this, but when you deal with one first-hand, reality hits hard. I know my horse well, and I knew we were in an emergency situation. I owe a huge debt of gratitude to Drs. Montesano, Tallarico, and La Croix for saving ET’s eye and for continuing to guide his follow-up care.