We're going to do a little experiment. Make sure you watch this part of the tutorialin full screen. Close or cover your left eye, look at theplus sign. Be aware of the circle, but don't focus on it! Keep looking at the plus. You may need to move your head back and fortha little bit, or move your thing closer to your face. But at some point, the circle isgoing to disappear. Now close your right eye and look at the circle.Move your head back and forth until the plus sign disappears.
You've just found your naturally occurringblind spot in each eye. And of course daily practice we do not notice this. The human eye has what you might call a fundamentalflaw. Lightsensing cells in your retina send signals to your brain via nerves. And thosenerves are in front of the lightsensing cells. Eventually, those nerves have to pass throughthe back of your eye to get to your brain and in the part of your retina where theypass through, there aren't any lightsensing cells. That's your blind spot. Now this isn't normally a problem, becausethe blind spots are located at slightly different
points in each eye, and each of your eyeswork together to fill in a complete picture. But even with one eye closed, you're notseeing a big black hole. Instead, your brain fills in what it figures ought to be there.That's why, when the circle disappears, you see the color of the background. Yourbrain is guessing, and it's guessing wrong. Although! At least one very small study foundthat you might be able to shrink your blind spot with practice. Researchers showed ten participants an imagethat fell within the margins of their blind spots and asked them to describe it. By theend of the experiment, people got a little
better at describing those images. The researchers think it's because the lightsensingcells right around the edges of the blind spots became more sensitivebetter at pickingup and passing on light signals. That's the kind of skill that's probablynot going to ever make any kind of difference in a lifeordeath situation, and humans havehad blind spots in their eyes for as long as we've had eyes. But it's a neat wayto try and hone your brain, if you're into that sort of thing. There is a different kind of creature, though,that just completely avoids this problem.
Cephalopods, like octopuses and squids, havetheir nerves behind their lightsensing cells, so there's no need for them to have a blindspot. Why did we not do it that wayé Evolution.Well I, for one, welcome our tentacled overlords. Thank you for asking, and thank you especiallyto all of our patrons on Patreon who keep these answers coming. If you'd like to submitquestions to be answered, or get these Quick Questions a few days before everyone else,you can go to patreon scishow. And if you just want to keep getting smarter withus, you can go to scishow and subscribe! Just do it.
What do I do to treat an ocular migraine
Often ocular migraines can start with a visualdisturbance, followed by a throbbing headache. These disturbances don't always occur forall people, but if you are driving and you see zigzags of light, flickering lights or enlarging blind spots in your side of your vision, pull over as a safety precaution until the visual disturbance goes away. For most, the typical treatment usually entailsoverthecounter pain medications. For people who have frequent migraines, it is recommendedto keep a log book to keep track of certain foods that have been known to trigger migraine headaches. Some of these are: cheese, red wine, smoked meats, chocolate and caffeinated drinks. Also,make note of nightly sleeping hours activities
and times of emotional stress, as these patternscan also be helpful in determining possible triggers to your migraines. If you experience ocular migraines, book anappointment with your of Optometry. You don't need a referral to see your optometrist,and many optometrists can see you on the same day if you are experiencing pain. Remember,it's important to call your optometrist whenever you experience unusual visual symptomsto rule out sightthreatening conditions that require immediate attention.