Veterinarians at San Diego Zoo and a team of doctors have carried out cataract surgery on a three-year-old gorilla.
The procedure on Leslie, a female western lowland gorilla, was undertaken by a cataract surgery specialist who has treated thousands of humans, but never any other type of primate.
San Diego Zoo Safari Park associate veterinarian Meredith Clancy said the gorilla suffered from increasing blindness in her left eye due to a possible injury from playing or climbing.
"It is a really unusual thing for us to see," Dr Clancy said.
A team of animal care specialists, including ophthalmologists and anaesthesiologists from the University of California San Diego Health, carried out the surgery on December 10, but it was only announced on Monday.
A cataract is a clouding of the clear lens behind the iris. It typically develops as part of a normal aging process, but can also be caused by trauma to the eye.
Once a cataract develops, the lens becomes progressively cloudier and vision deteriorates.
Cataract surgery specialist Chris Heichel and his team used a specialised microscope and instruments using gentle suction to remove the cataract in Leslie's left eye.
The medical team removed Leslie's cloudy lens and inserted a new artificial lens that provides the gorilla with clear vision.
Dr Heichel said he had performed thousands of eye surgeries on human patients, ranging in age from one day to 105 years, but this was his first surgery on a gorilla.
"Fortunately, the similarities between the anatomy of human and gorilla eyes are great enough to allow us to safely navigate the procedure without complication," Dr Heichel said.
"The remainder of the eye appeared to be in excellent health, indicating exceptional vision potential for the rest of Leslie's life."
Leslie is already back in her Gorilla Forest habitat at the San Diego Zoo Safari Park but the team is monitoring her healing process closely, as there remains the possibility the new lens could become cloudy.
"The eye has an envelope that holds the lens in place. It should remain clear, but sometimes after cataract surgery, the envelope will get a little cloudy," Dr Heichel said.
"In a human patient, we can laser the envelope to remove the cloudiness. That might not be quite so easy for Leslie, therefore I made a little opening in the back of the envelope to maintain her clear vision in the future."
The zoo's animal care team sedated Leslie's 31-year-old mother Kokamo, as they were concerned she might be upset about Leslie's absence from the gorilla habitat during the procedure.
