Romina, a 21-year-old Western lowland gorilla at Bristol Zoo Gardens, west England, had congenital cataracts in both eyes.

Ophthalmic surgeon Jenny Watts from the Royal Hampshire County Hospital in Winchester removed one cloudy cataract and replaced it with a silicon lens -- the first such operation performed on an adult gorilla in Europe, according to the zoo.

Watts said the half-hour operation was no different from treating a human for cataracts -- apart from a "pungent aromatic smell" emanating from her hairy patient.

"The hardest bit is the anesthesia because it's critical to ensure that the gorilla remains completely unconscious throughout the operation," Watts said.

It took an hour and a half for 120-kg Romina to be tranquilized, allowing the surgeon to make an incision through the cornea before breaking up the cataract with ultrasound and inserting the silicon lens.

Once Romina recovered she was reunited with her companions Bongo and Salome -- and there may be romance in the air.

"Romina had led quite a reclusive life -- but now she's even interacted with a male for the first time," said Watts.

A second cataract operation was being planned to restore Romina's bilateral sight, the zoo said in a statement.

Western lowland gorillas can live to about 50 years and come from areas of dense rain forest and swamp in African countries including Nigeria, Cameroon, Gabon, Equatorial Guinea and the Central African Republic.