Gazing at a blue sky, you may see shapes drifting through your field of view—blobs and squiggles called floaters. Why do they jump away when you try to get a better look?
Look at the blue sky or a white wall, or lean in closely to an all-white computer screen, and let your eyes relax. Do not look directly at the sun! Gaze around without focusing on anything in particular. What do you notice?
You may see small shapes—dark blobs, light ribbons, strange squiggles—that seem to drift across your field of view. What shapes do you see? Do they remind you of anything?
What happens when you try to look directly at them?
Your eyeball is filled with a clear, jelly-like substance called vitreous humor, which helps the eye maintain its shape. Inside the vitreous humor, dead cells and stringy bits of protein cast tiny shadows on the retina, shadows that are responsible for the floaters you see in your field of view.
When you notice a floater, you may shift your gaze to look at it, only to find it seems to jump away from your glance. Floaters stay roughly in the same place in front of your retina, so moving your eye to look at them causes the floaters to appear to move, too.
People of all ages can have floaters, but they become more common as we get older. Some floaters are stable for many years, while others come and go over a period of weeks or months. Floaters are usually easy to ignore and thus don’t present a problem for most people. However, a sudden dramatic increase in floaters can be an indication of a retinal detachment and should be checked by an eye doctor.
Despite the name, many floaters tend to sink to the bottom of the eye. If you happen to be lying on your back, this tendency puts the floaters directly in your line of sight as you gaze up to the sky—an optimal arrangement for viewing.
Where do your floaters seem to be floating? They appear to hover in your field of view, so when you look at the sky, you see them as being in the sky. Though you’re actually seeing shadows cast by bits of material in your eye’s interior, your brain can’t comprehend seeing something happening inside the eye, so it “projects” the floaters out into your field of view.
This Science Snack is part of a collection that highlights Black artists, scientists, inventors, and thinkers whose work aids or expands our understanding of the phenomena explored in the Snack.
Source: Wikimedia Commons
Dr. Patricia Bath (1942-2019), pictured above, was an ophthalmologist and laser scientist, and was the first woman chair of ophthalmology at a US university. She studied the causes of and cures for blindness, and invented a widely used method of using laser surgery to treat blindness caused by cataracts. Dr. Bath also co-founded the American Institute for the Prevention of Blindness. This Science Snack can help you investigate the structures in the eye that help you see, so you can understand the eye like Dr. Bath did.