A Wilder View: Why animals don’t need glasses

Eagle Head
Posted at 10:46 AM, May 31, 2023
and last updated 2023-05-31 12:46:25-04

MISSOULA — People sport stylish frames to improve their vision or simply enhance their looks. But our wild counterparts don't follow suit.

Hold onto your spectacles because our wildlife correspondent Tanner Saul explains why animals don't need glasses in this edition of A Wilder View.

People who wear glasses know it can be to live without them — but why don't animals seem to have the same problem?

According to the U.S. Centers for Disease Control and Prevention (CDC), 64% of adult Americans need glasses.

Even though most people need glasses most would consider their vision to be the most valued sense.

“Some of us need glasses at a young age and others don’t. And that’s probably the case in animals as well,” Visual Ecologist and Animal Behaviorist Dr. Eleanor Caves.

You’ve probably described some people as blind as a bat or eagle-eyed — and those can hold some truth.

“Indeed, there are big differences even among let’s say goldfish. Just some goldfish have good vision and others don’t,” Dr. Caves said.

People who head to the ophthalmologist can tell them which lines on the eye chart are blurry, but with animals, there’s obviously a language barrier.

We can’t ask Steve the giraffe if one or two is better.

So, scientists like Dr. Caves have to come up with some unique methods to figure this out.

“You get a round cylindrical tank, and you put an animal in the tank. Then you line the sides with vertical black and white stripes. And you rotate the stripes. And if the animal can see the stripes it’s going to rotate its body to try and stabilize its visual world. At a certain point, you’ve reached the animal’s acuity limit and so it won’t spin its body anymore because it doesn’t actually see that there is motion happening.” - Dr. Eleanor Caves.

Even with all these tests, it’s hard to discern how each animal perceives vision.

For instance, in people, the image projected onto the back of our eyes is upside down. But our brain then decodes this image so that we perceive it the right way up. There may be unknown ways animals decode the image from their eyes.

“Are there then things in the brain or higher order centers that post-process the image and enhance the contrast or sharpen edges,” Dr. Caves said.

So how do we know if they’re seeing it in 4K or VHS?

“In your eye, you have the retina and on the retina there’s photoreceptors. You’ve heard of probably your rods and your cones. If your eye was a camera, the number of photo-receptive cells that you have is sort of like the number of pixels in the image,” explained Dr. Caves.

Finding the key to ways different animals use their vision can enhance our own lives too.

“As we work on miniaturizing camera technology -- nature’s already done that for us in the form of jumping spider eyes,” Dr. Caves said.

One of the primary challenges people face today is the insane amounts of digital information there is.

Dr. Caves says animals may already have the answer.

“I think of a lot of these visual systems as natural compression algorithms, and they’ve already figured out how to keep the relevant bits for behavior while getting rid of a lot of the fluff.”

It turns out that eyes in the animal kingdom are complicated, but I hope we’ve given you more clarity.