Bird’s eye view – safeguarding penguin vision

Dunedin Wildlife Hospital treats more than 600 native animal patients annually, including hoiho, kākāpō, kiwi, kea and tuatara. In recent years, the hospital’s researchers have observed an increase in hoiho presenting with eye lesions following the migration of fish species, particularly blue cod. “Such changes in prey availability may force the penguins to adapt their hunting strategies, increasing the risk of injury,” said Dr March de Ribot. “As they venture farther afield in search of food, they encounter new threats, including fishing gear and pollution, which can cause traumatic eye injuries.”

The obvious first port of call for sick avians would be veterinary surgeons, who do receive ophthalmology training, but sometimes hospital staff need to discuss cases with an ophthalmologist. While working with vets in this environment is “very rewarding and a pleasure”, said Dr March de Ribot, treating penguins’ eyes has been a challenge and an education. For a start, their eyes have evolved for aquatic life, with some features quite different from human eyes, he said. These differences have been discussed in detail by fellow penguin eyecare supporters, Drs Peter Hadden and Jie Zhang from the University of Auckland, in their 2023 paper, ‘An overview of the penguin visual system’.

“The nictitating membrane is a translucent third eyelid that protects the eyes from debris and ultraviolet light, acting like a pair of goggles when they are swimming underwater,” said Dr March de Ribot. They also have a flattened cornea, a more spherical lens and see colours differently. “They perceive violet, blue and green, but not red, which is believed to be an advantage underwater.” Other adaptations include a thickened sclera, which provides protection and structural support and is particularly useful for resisting pressure in deep water, he said.

Chilled-out birds, chilly surgeons

These physiological differences require a different approach to examination for an ophthalmologist used to treating humans. As wild animals, penguins become stressed and uncooperative during medical examinations, said Dr March de Ribot. “Giving them a mild sedative allows a more detailed examination and ensures the safety of the animals. We then do several examinations at the same time.” The ambient temperature in the treatment room is also carefully controlled to maintain a cool environment, suitable for the penguin but less than ideal for human hands. “But we’re used to the cold in Dunedin!” he said.

Despite limited resources, the dedication of staff and volunteers ensures that every effort is made to safeguard the sight of these magnificent birds, said Dr March de Ribot. “We can perform cataract surgery with good results, but penguins cannot have post-operative steroids, which dramatically increases the risk of infection.” For examinations, Dr March de Ribot is usually armed with an adapted portable slit lamp or a direct or indirect ophthalmoscope. “But the nictitating membrane and the fact that penguin pupils do not respond to cycloplegics make direct retina examination challenging.”

Being involved with animal care is gratifying and the experience has helped Dr March de Ribot to be more patient, he said. “Studying penguin eyes offers insights that could benefit human vision care, especially for non-verbal patients – veterinarians rely on external signs and behavioural cues to diagnose eye conditions.”

Most importantly, however, is the question of what these patients are like to be around. “Penguins are very fluffy to the touch,” was his unruffled response!