Seals see better in the water than they do on land.
Seals are a member of the pinniped family, referring to their flippers that allow them to thrive on both land and sea. Unlike other pinnipeds, such as sea lions and walruses, seals do not walk on all fours. Instead, they writhe on their stomachs to move across land. The common seal averages 4.5-5 feet long, with the males being slightly larger than the females. The lifespan of seals varies due to a high rate of early mortality; if a seal survives infancy, they often live longer than 30 years. Like humans, seals maintain a body temperature of 98.6 degrees Fahrenheit.
Seals have evolved to see especially well underwater, allowing them to see prey in the low-light depths of the sea. Their large pupils close up when seals are on land, protecting their eyes from increased sunlight.
In 2012, Dr. Doug Esson, BVSc, MRCVS, DVM, DACVO performed cataract surgery on then four-month-old Iris, a Pacific Harbor Seal that was rescued by SeaWorld animal rescue team in San Diego, CA. Iris was functionally blind and unable to hunt for food leaving her severely dehydrated and underweight. After a successful operation and three months of rehabilitation Iris’s vision has been restored and she is ready to return to the sea.