Complex Surgery Saves Horse's Eye After Fungal Infection

Cassie with Drs. Kim and Adelman.
Cassie with Drs. Kim (L) and Adelman (R).

Cassie, a 17-year-old Oldenburg mare, was referred to the UC Davis veterinary hospital’s Ophthalmology Service for a stromal abscess in the left eye. Stromal abscesses can result in significant inflammation and pain and often require complex (and expensive) surgery to prevent blindness or the need to surgically remove the eye. Thanks to the combined expertise of the Ophthalmology, Equine Internal Medicine, and Anesthesiology Services, Cassie was able to undergo specialized surgery that resolved the issue and preserved her vision.

The corneal stroma, the thickest layer of the cornea (the clear part at the front of the eye), is essential for vision. A stromal abscess can occur when bacteria or fungi penetrate through an injury to the outer layer of the cornea (the epithelium). As the body tries to heal the wound, it can trap bacteria or fungi in the deeper layers, causing inflammation of the cornea, as well as inside the eye. The abscess often appears as a white or yellow-colored focal cloudiness in the cornea.

Drawing of the layers of the cornea.
Layers of the cornea showing the location of the stroma, the thickest layer.  Created with

In Cassie’s case, the infection was due to a fungus that is common in California and spreads easily, particularly on windy days. Although they can advance quickly and result in serious problems in just a few weeks, fungal infections in the eye take a long time to treat. The fungus likes to grow deep into the cornea, where it is hard to treat effectively with eye drops.  
In some cases, the affected eye has to be removed because the fungus is so aggressive, and treatment cannot control it. For cases that respond to medical treatment, the total treatment time can be weeks to months.

When Cassie came to UC Davis, she was suffering from severe inflammation in her eye due to the infection. Instead of medical management, the team opted for surgery, performing a deep lamellar endothelial keratoplasty (DLEK) to remove the infection and stabilize the cornea so it could heal. The success of this complex surgery required significant team effort. 

Picture of cloudy eye due to stromal abscess.
The corneal stromal abscess in Cassie's left eye showed a characteristic cloudy appearance.

“The surgery can save the eye, and, when successful, the treatment time is greatly reduced compared to medical treatment,” said Dr. Soohyun Kim, an assistant professor of ophthalmology who was involved with the case.

The procedure includes dissecting up the front half of the cornea (that is healthy), removing the deep area of the cornea that contains the fungus and replacing it with a “button” of equine donor corneal tissue, and then suturing the front half of the cornea back down into place.

“This procedure is a big undertaking,” said ophthalmology resident Dr. Sara Adelman, who was part of the surgical team. “Time was of the essence.”

Cassie's eye two months after surgery with the cloudiness mostly resolved.
Cassie's left eye two months after surgery.  It is normal for corneal edema (blue color) to persist for up to a few months after surgery.

After the surgery, a subpalpebral lavage (SPL) catheter was placed in Cassie's lower eyelid to facilitate treatment with ophthalmic solutions. She stayed at the layup facility at the Center for Equine Health, where the Ophthalmology Service closely monitored her recovery over the following weeks. 

The process of corneal remodeling generally continues for weeks to months. Cassie will have a small circle of scar tissue in her cornea, but it should not significantly affect her vision. The team credits the swift action of the client and the referring veterinarian with giving the treatment the best chance of success.

Picture of a subpalpebral lavage (SPL) catheter leading into horse's eye.
A subpalpebral lavage (SPL) catheter was placed to make it easy to deliver medications after surgery.

Cassie has recovered and is back at home with her owner.