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The next time zookeepers toss a fish snack to Nika the seal, they expect she'll catch it — just as she used to before cataracts clouded her vision.

Veterinary specialists from Florida were brought in Thursday to help the medical staff at Utah's Hogle Zoo to remove cloudy lenses from each of her eyes.

After two hours of surgery, four hours under anesthesia, Nika was "working on waking up," said zoo spokeswoman Erica Hansen, declaring the operation a success. "She's recovering slowly but is still pretty groggy."

Nika's vision problems first appeared 1½ years ago, said Janine Bartling, primary keeper in the zoo's Rocky Shores exhibit, which features bears, sea lions and otters as well as three harbor seals.

At first, keepers weren't sure if there was something wrong or just "Nika being Nika," Bartling said, since Nika was the most laid back of the seals.

But when she couldn't catch fish thrown her way, the staff became more concerned.

They conducted experiments to pin down what was going on, testing her peripheral vision and her ability to follow the motion of falling cotton balls. They checked to see if the issues were the same on sunny days as shady, indoors versus outdoors.

Keepers increased their observations of Rocky Shores' other inhabitants to see if they were having any problems similar to Nika — they weren't — and over time the filmy presence of cataracts became more obvious, first in her left eye, then in the right.

"They can be common in animals and people, especially with age," said Nancy Carpenter, Hogle Zoo's associate director of animal health, even though 13-year-old Nika, barely middle-aged in harbor-seal years, is young to have cataracts.

Cataract surgery can be risky with pinnipeds — the group of marine mammals with front and rear flippers, including seals, sea lions and walruses. Pinnipeds have a "dive reflex" that can cause their heart and breathing rates to slow markedly, posing a real challenge for an anesthesiologist to maintain a healthy balance.

While Hogle's medical team is capable, Carpenter said zoo officials decided to bring in a pair of experts from Florida who travel around doing this type of surgery — veterinary ophthalmologist Carmen Colitz and veterinary anesthesiologist James Bailey.

A team of nearly a dozen doctors and assistants went to work on a sedated Nika shortly after 9 a.m. Through operating-room windows, their every move was observed by the media and a half dozen anxious keepers from Rocky Shores, doting over one of their family.

"We have the best of the best [doctors] here so we know she's in good hands," said keeper Maggie McGrath, admitting she was a bit nervous still. "We love her."

The way things went, McGrath and her colleagues will have plenty of future time with Nika. And they'll have their hands full.

She's going to have to be out of the water for three weeks — not easy for a seal — so Bartling and the keepers have devised some dry-land exercises to keep her occupied.

And what does Nika like?

Pushing balls with her nose, for one, and rubbing her back on the chamois-like felt material found at car washes.

"Anything that's tactile or smells is fine with her," Bartling said.

mikeg@sltrib.com