Fish, reptiles, birds and some mammals have an additional eyelid that is called a nictitating membrane. It is more or less transparent and unlike our eyelids it moves sideways across the eye. As well as protecting the eye it also helps with cleaning and lubrication.
A falcon diving at 200mph has good reason to want to want a pair of goggles to protect its eyes from insects and debris. Some birds also close their third eyelid when feeding their young in the nest. All those eager beaks can be dangerous. Fish use it similarly to protect their eyes from debris in the water.
21 of the 22 species of primates also have a nictitating membrane but there is a spectrum of how much it can cover the eyeball - 10% in the case of Gorilla gorilla all the way through to 100% in Perodicticus potto (above).
Humans also have a remnant of the nictitating membrane where it is called the plica semilunaris. The muscles that would make it functional have degraded to the point where they're practically non-existent.
Like many other vestigial features it is still doing something useful. It functions during movement of the eye, to help maintain tear drainage and to permit greater rotation of the globe. Evolution is very adept at putting redundant stuff to new uses.
Creationists often try to dismiss the evidence of vestigial features by pointing to its reduces function, but in biology vestigial refers to an organ which is greatly reduced from the original ancestral form and is no longer functional or is of reduced or altered function.
Our third eyelids are another clue to our common ancestry with all other living things.
Evolution is a Fact - Index #1-20
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Evolution is a Fact #21 - Footprints in the Sand
Footprints at Laetoli show our Australopithecus afarensis ancestors were bipedal 3.6 million years ago.
Evolution is a Fact #22 - The Hillocks of Hiss
A vestigial feature if the human ear shared by 10% of the population demonstrates our evolutionary history.
Evolution is a Fact #23 - Faunal Succession
The consistent sequence of fossils found in the rocks can only be explained by evolution.
Evolution is a Fact #24 - The Origin of Your Inner Ear
How the bones that reptiles eat with became the bones that we hear with.
Evolution is a Fact #25 - Deep Time
Scottish geologist Andrew Hutton discovered the proof of earth's great antiquity.
Evolution is a Fact #26 - Colour Vision
How gene duplication - new "information" -and mutation equipped us with trichromatic vision.
Evolution is a Fact #27 - Monkeys, Typewriters, Shakespeare, 747s etc.
Evolution is a combination of random mutations and non-random selection.
Evolution is a Fact #28 - Something Darwin Didn't Say
A long term study of pigeons demonstrates how natural selection acts on a local population
Evolution is a Fact #29 - Use it or Lose it
Fossil genes reveal the history of modern species
