Corneal transplants have a high success rate
With compassionate foresight, people who are facing the euthanasia of their companion animal can make a choice that may save the eyesight of an animal patient in the future.
Dr. Bianca da Costa Martins, an assistant professor of ophthalmology who recently joined the University of Illinois Veterinary Teaching Hospital in Urbana, performs transplants, or grafts, to restore strength to damaged or infected corneas in horses or dogs. She is in the process of setting up a corneal bank, which relies on donations from the owners of animals at their life’s end.
Save Eyesight, Save a Life
The cornea is the clear, dome-shaped surface that covers the front of the eye. It is a key component in vision because it allows the light into the eye and it controls and focuses the light. The cornea also protects the interior structures of the eye from injury and infection.
FAQs about the Corneal Bank at Illinois
- What about creating a corneal bank for cats? Because the graft procedure is more complicated in cats, Dr. Martins is starting her program with dogs and horses. Cats may be included in a later phase of the program.
- Can I sign up to donate my animal’s cornea? Because the tissue has to be collected by a trained veterinarian within an hour of the death of the donor animal, only owners whose animals are euthanized at our hospital will be asked to consider donating the tissue.
- Is this just like a cornea transplant for people? Not exactly. Because it is cost prohibitive to do live-tissue transplants for animals as is done routinely for people, the transplanted tissue that has been cryopreserved will be opaque. It restores the structure of the eye when part of the cornea must be removed because of disease or injury. However, the animal often can still see with the remaining part of the eye.
“The purpose of this bank is to have corneas available for patients that would benefit from a corneal graft,” explains Dr. Martins. “That includes horses with an abscess in one of the layers of the cornea as well as horses and dogs with such conditions as deep corneal ulcers, corneal perforation, and iris prolapse, which is when there is a hole in the cornea and the colored part of the eyeball starts to come out.”
The bank will use the healthy corneas of patients who are euthanized at the Veterinary Teaching Hospital only if the owners choose to make the donation.
“We understand that this is a grieving time for the client. It may be of comfort to know that their beloved animal’s corneas could save the eyeball, eyesight, and even the life of other patients,” says Dr. Martins.
Cryopreservation Used for Corneal Bank
The process of collecting the corneas happens within an hour after euthanasia, as Dr. Martins describes: “The procedure is performed by an experienced veterinarian after a brief ophthalmic evaluation to ensure that the corneas are not damaged. After collecting the corneas, the animal’s eyelids are respectfully sutured closed.”
The corneas are then frozen and stored at -80 degrees Celsius and will be available for use for up to one year. Most of the corneas utilized in veterinary medicine are preserved in this way through a process called cryopreservation.
“The corneal cell walls will be devitalized by the cold temperature, and the graft will be basically a rich source of thick collagen,” explains Dr. Martins.
The most common type of graft, called a tectonic graft, is used to give structure back to the cornea in damaged eyes. “We replace the piece of tissue that is missing in the patient’s cornea with a piece of the donor cornea. This procedure provides structural, collagen support for a weakened, missing, or infected cornea.”
Grafts Restore Corneal Integrity
After a thorough ophthalmic examination, a veterinarian will decide whether the patient would benefit more from a corneal graft or from another procedure, such as a conjunctival graft or synthetic collagen membrane.
“In the case of a corneal graft, the cornea’s thickness is immediately restored following surgery. A corneal graft also allows better vision through the graft itself,” explains Dr. Martins.
“It is important to note that some opacity in the eye is expected after a graft with a cryopreserved cornea. Scar tissue will inevitably form since the graft is being placed into a cornea that has damage and inflammation already. Depending on the size, depth, and location of the scar tissue, vision may be affected,” says Dr. Martins.
Although the introduction of new, foreign tissue into a body in a graft always carries a risk of complications, corneal transplants have a high success rate.
“We define a positive outcome as a restoration of the corneal integrity. An opaque graft in a comfortable but non-visual eye is still considered successful,” says Dr. Martins. “In horses undergoing corneal transplantation, a positive outcome is observed in 78 percent to 98 percent of the cases.”
As Dr. Martins collects specimens for the corneal bank, corneal grafts will be provided to animals in need of them. “Although all corneal transplants in animals vascularize and become opaque, they are associated with high success rates and good visual outcomes,” says Dr. Martins.
By Melissa Giese