Dublin Zoo has performed the first ever recorded cataract surgery on a common hippopotamus worldwide.
Imani, an 18 year old female hippo, underwent the historic cataract surgery at Dublin Zoo in August and has since made a full recovery.
The operation has restored the sight in her left eye, in a joint effort involving the zoo's animal care and veterinary teams working alongside specialist surgeons from France.
Dublin Zoo said the operation took months of planning to ensure Imani was ready for the life-changing procedure.
Imani arrived at Dublin Zoo from Antwerp earlier this year as a companion for Heidi the hippo. The team quickly spotted that she was extremely cautious in her new surroundings and kept tripping over things.
They later discovered that Imani had a long-standing visual impairment and was completely blind in her right eye. There was some hope of restoring her vision in her left eye with cataract surgery to improve her lived experience, so they decided to give it a shot.
"This is a ground-breaking operation, and an extraordinary technical achievement, however our primary concern was always Imani’s welfare." said veterinary surgeon at Dublin Zoo Frank O'Sullivan.
"We don’t believe there is a record in scientific literature of any such operation, much less a successful one, being conducted on a hippopotamus anywhere in the world," he added.
One of the biggest challenges for the team at Dublin zoo was figuring out how to administer the anesthetic to an animal that weighs 1500kg with thick skin that’s two inches deep.
The vets discovered a small triangle of skin behind the hippos jaw which was a little thinner which enabled them to administer the medicine. The veins under the hippo's tongue were used to administer the anesthetic intravenously during the operation.
The success was dependent on a carefully planned post-operative care as keepers were tasked with giving her eye drops four times daily and with strict instructions to keep the hippo out of the water, which they achieved with patience and care.
"There was huge risks involved in giving the eyedrops because of the hippos huge mouth which could easily take your hand off," said team leader of the Africa section, Helen Clarke-Bennett.
The team discovered Imani could be placated with some of her favourite foods including Chinese cabbage, pak Choi and lettuces as well as some handfuls of hay to distract her.
Vets at the zoo said the operation has given Imani a new lease of life with a noticeable change in her behaviour since her eyesight has improved.
She now responds to visual stimuli, navigates obstacles with ease and is much more confident in her movements, and can even run once again.
A bespoke "hippo fit bit" has been attached to her front leg to monitor her movements post-surgery.
The sensor bracelet is an accelerometer and provides Dublin Zoo with a real-time summary of Imani’s activity over a 24-hour period, helping to understand her normal behaviour patterns and assess any variations that may indicate issues.
"Now that she has improved sight, it’s been great to see her become much more confident and active. It’s a powerful example of Dublin Zoo’s commitment to providing world-leading animal welfare," said Behaviour and Welfare Scientist at Dublin Zoo Lucy Stratford.
The operation will be documented for publication in peer-reviewed veterinary literature to educate and inspire other zoological organisations worldwide, paving the way for other zoos to use the same sensors with animals in their care.
Veterinarians said that hippos can live well into their forties, so Imani has many years of quality life ahead of her in her enclosure at Dublin zoo.
Common hippos such as Imani, live across sub-Saharan Africa in rivers, lakes, and swamps with reliable year-round water.
The species is listed as vulnerable on the IUCN Red List, facing a high risk of extinction due to habitat loss, poaching, human–wildlife conflict, and changes to water systems from dams and climate change.
Populations have fallen by more than 30% in recent decades.
