Tuesday, May 30, 2006

Zoo’s Eagle Regains Eyesight After Surgery

By Patrice Scott

Known for their keen eyesight, bald eagles can see a rabbit from a mile away, and their vision is at least four times sharper than that of a human with perfect eyesight. When a bald eagle swoops down from several hundred feet to catch a fish, the bird's powerful talons skewer its prey with 1,000 pounds of pressure per square inch.

When Alaska, a 32-year-old female bald eagle at Sunset Zoo in Manhattan, Kan., wasn't eating food unless it was placed directly in front of her, zookeepers knew there was a problem. And, her eyes had a cloudy appearance, the telltale sign of cataracts.

Ryan Gulker, general curator at Sunset Zoo, said Alaska's situation progressed rapidly. "It was surprising how quickly this happened."

Exotic animal medicine veterinarians at the Veterinary Medical Teaching Hospital at Kansas State University confirmed Alaska had cataracts while performing an annual wellness examination. Zookeepers and veterinary specialists monitored her situation, which was clearly worsening.

"The keepers observed that she was bumping into obstacles, like branches and perches, when she tried to change her position or when she'd get startled," said Dr. Connie Ketz-Riley, clinical assistant professor in exotic animal, wildlife and zoo animal medicine. "She wasn't consuming food unless it was right at her feet."

Dr. Rachel Allbaugh, ophthalmology resident, said Alaska was fortunate to be in captivity given her handicap. "Were she in the wild, she would have starved to death."

Dr. Harriet Davidson, professor of ophthalmology, explained to zookeepers that Alaska's vision could be corrected with phacomulsification, a procedure to remove cataracts. She said that cataracts impair vision by robbing the eye of light. "By removing the opaque lens, or cataract, light is able to penetrate to the retina and this is what allows vision."

The veterinary specialists met with zookeepers and presented their options.

"After consulting with the veterinarians and the specialists in the ophthalmology department, we weighed the pros and cons and the pros won," Ryan said. "Even though she is an aged bird, we could improve her quality of life."

Once the procedure was scheduled, it required intense preparation to minimize the bird's stress. "We did everything possible to reduce her time in confinement for surgery," Ketz-Riley said. "We caught her mid-morning and brought her to the teaching hospital. She was given an ophthalmologic exam to evaluate the structure of the eye and retinal function. Her retinal function was normal in both eyes so we decided to proceed."

Surgery offered abundant challenges because of the bird's eye structure, age and stress level. Because of these factors, there would be additional risks associated with anesthesia.

Alaska was placed in a deep plane of anesthesia because of her complicated eye structure. An eagle's eyelids close during sleep, but they also have a nictitating membrane, or third eyelid, that sweeps dirt and dust from the cornea about every three seconds. "When anything touches the eye, it triggers muscle movement and the third eyelid protrudes," Ketz-Riley said. "This needed to be neutralized for surgery. We had to keep her in a deeper anesthetic plane, which increases the risk for the bird."

For one and a half hours, Davidson and Allbaugh performed microsurgery on Alaska. Ketz-Riley said they knew soon after surgery that it was a success. "The surgery could not have gone better. As soon as keepers put her food down, she went right after it."

Three weeks later, the specialists were able to examine Alaska and evaluate her progress. "We were thrilled at how great her eyes looked," Allbaugh said, adding it was difficult waiting so long to examine the bird. "We wanted to examine her, but we didn't want to take the chance of stressing her or causing her to tear her sutures that are the size of a strand of hair."

Now when visitors to Sunset Zoo stop by to see Alaska, she will be looking back at them, too.