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
Are Blue Eyes Endangered
Despite the apparent prevalence of the traitamong swanky crooners and British spies and creepy old creatures who just hung onto thering for too long, only about 8% of the world's human population has blue eyes. Here in theU.S. it's about twice that, but that's still a lot less than it was at the turn of thetwentieth century when nearly half of all Americans had the trait. So what happenedéAre blueeyed humans going the way of the dodoé Well, no. We cleared up that rumor about redheadsgoing extinct; the same goes for blue eyes. While the trait is becoming more rare, it'sunlikely it will disappear all together. Which
is crazy when you consider that 10,000 yearsago blue eyes didn't even exist. In fact, there's a good chance that blueeyed peoplemay all share one common ancestor. Studies over the past decade have actually tracedthe trait to a mutation that most likely arose among browneyed people in a single humanin the Black Sea region of southeastern Europe between 6,000 and 10,000 years ago. The mutation affected what's known as theOCA2 gene, which helps our bodies produce melanin, the brownish pigment that gives colorto our hair and eyes and skin. The mutation created kind of a dimmer switch for the pigmentation,but it didn't affect the entire gene. Instead,
it only affected the production of melaninin the iris, the ring structure around the eye that regulates how much light gets in. The bulk of the iris is a thick layer of melaninproducingcells called the stroma. And the OCA2 mutation turns the production of melanin in the stromaway down, but the pigmentation still shows up elsewhere, like in the hair and skin andother parts of the iris. Basically, the mutation keeps the stroma from being brown. So why blue thené Well, strictly speaking,blue eyes aren't actually blue. Instead, in people with this mutation, the stroma is fullof nearly colorless cells. And when the light
strikes them, they scatter the wavelengthsback out, in a process similar to what makes smoke or fog look blue when light passes throughthem. If there is some yellowish pigment in thestroma, then the blue light will combine with that to make green. Throw in a little bitof brown, and you have hazel. So how did we go from having no blueeyedpeople, to hundreds of millions of them in less than 10 millenniaé No one's entirelysure why the trait spread so quickly through Europe. Some scientists think the mutationcould have helped prevent certain eye disorders related to long, dark northern winters.
But another factors appears to be that, forwhatever reason, lots of blueeyed people simply mated with other blueeyed people inthe past, which kept the trait in circulation. Because for each of your genes, you have twodifferent versions, called alleles, one from your father and one from your mother. If youhave at least one dominant allele for a gene, that's the trait you have. The blue eyes come from a recessive allele,which means if you inherit one allele for blue eyes and another for brown, you're goingto have brown eyes. But you still carry the recessive blue allele, which can be passedon. Which means that that first person that
had that blueeyed mutation didn't have blueeyes. They had to pass that onto their children, and their children had to pass it onto theirchildren, until eventually they came back together to make someone with two blueeyedalleles. When both parents have blue eyes, they bothhave two recessive blueeyed genes, which means their children will also have blue eyessince there's no dominant gene to mask the recessive one. This is how you end up withScandinavian countries that are 95% blueeyed, and it also explains why the percentage ofblue eyeers is dropping in much of the western world.