Eye Floaters Ted Talk

What are those floaty things in your eye Michael Mauser

Have you ever noticed something swimmingin your field of visioné It may look like a tiny wormor a transparent blob, and whenever you try to geta closer look, it disappears, only to reappearas soon as you shift your glance. But don't go rinsing out your eyes! What you are seeing is a common phenomenon known as a floater. The scientific name for these objectsis Muscae volitantes,

Latin for quot;flying flies,quot; and true to their name,they can be somewhat annoying. But they're not actually bugsor any kind of external objects at all. Rather, they exist inside your eyeball. Floaters may seem to be alive,since they move and change shape, but they are not alive. Floaters are tiny objectsthat cast shadows on the retina, the lightsensitive tissueat the back of your eye.

They might be bits of tissue, red blood cells, or clumps of protein. And because they're suspendedwithin the vitreous humor, the gellike liquidthat fills the inside of your eye, floaters drift alongwith your eye movements, and seem to bounce a littlewhen your eye stops. Floaters may be onlybarely distinguishable most of the time.

They become more visiblethe closer they are to the retina, just as holding your hand closerto a table with an overhead light will result in a moresharply defined shadow. And floaters are particularly noticeable when you are lookingat a uniform bright surface, like a blank computer screen, snow, or a clear sky,

where the consistency of the backgroundmakes them easier to distinguish. The brighter the light is,the more your pupil contracts. This has an effect similarto replacing a large diffuse light fixture with a single overhead light bulb, which also makesthe shadow appear clearer. There is another visual phenomenonthat looks similar to floaters but is in fact unrelated. If you've seen tiny dots of lightdarting about

when looking at a bright blue sky, you've experienced what is knownas the blue field entoptic phenomenon. In some ways,this is the opposite of seeing floaters. Here, you are not seeing shadows but little moving windowsletting light through to your retina. The windows are actually causedby white blood cells moving through the capillariesalong your retina's surface. These leukocytes can be so largethat they nearly fill a capillary

How we see color Colm Kelleher

You might have heard that light is a kind of wave and that the color of an object is related to the frequency of light waves it reflects. Highfrequency light waves look violet, lowfrequency light waves look red, and inbetween frequencies look yellow, green, orange,

and so on. You might call this idea physical color because it says that color is a physical property of light itself. It's not dependent on human perception. And, while this isn't wrong, it isn't quite the whole story either. For instance, you might have seen this picture before. As you can see, the region where the red and green lights overlap is yellow.

When you think about it, this is pretty weird. Because light is a wave, two different frequencies shouldn't interact with each other at all, they should just coexist like singers singing in harmony. So, in this yellow looking region, two different kinds of light waves are present: one with a red frequency,

and one with a green frequency. There is no yellow light present at all. So, how come this region, where the red and green lights mix, looks yellow to usé To understand this, you have to understand a little bit about biology, in particular, about how humans see color. Light perception happens in a paperthin layer of cells,

called the retina, that covers the back of your eyeball. In the retina, there are two different types of lightdetecting cells: rods and cones. The rods are used for seeing in lowlight conditions, and there is only one kind of those. The cones, however, are a different story. There three kinds of cone cells that roughly correspond

to the colors red, green, and blue. When you see a color, each cone sends its own distinct signal to your brain. For example, suppose that yellow light, that is real yellow light, with a yellow frequency, is shining on your eye.

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