Submitted by DreadMCYT t3_zwy1xl in explainlikeimfive
AirborneRodent t1_j1xhirm wrote
You know that machine the eye doctor makes you look into when you first start an eye exam? You look at a little circle with a picture in it (e.g. a picture of a hot air balloon), and the machine goes whrrrr whrrrr while the picture goes in and out of focus?
That's called an autorefractor, and it's able to (mostly) figure out how bad your eyes are all by itself. All the "which looks better, 1 or 2?" stuff afterwards is just fine-tuning the prescription from a starting point that the machine figured out.
So with babies, they can't do the fine-tuning part of the exam, but they can still look into an autorefractor.
This is actually very important for babies. The fine-tuning isn't super important, but if the baby has a very different prescription in one eye than the other, then the baby will start favoring their good eye at the expense of their bad eye. Their brain, as it grows, will literally stop paying attention to their bad eye. If it's not corrected in time, it can cause lifelong vision impairment in the bad eye.
Weary-Lie-3581 t1_j1xizj8 wrote
That's what happened to my little brother. One of his eyes was "weaker" than the other and his brain mostly gave up with it. Around 10 or 11, the optometrist suggested he wear an eyepatch on his good eye to force his brain to re-engage his bad eye. It mostly worked. Could've helped more, but he wasn't very consistent with it because he obviously had a hard time seeing.
Ulysse_B t1_j1z3jta wrote
You just learned me that, during my childhood i saw some childrens with a patch on one eye, it all makes sense now ! It's very facinating to see how the brain work
FriendlyFiber t1_j1y1ug0 wrote
Ah, amblyopia. I was diagnosed with this at age 6. Patching somewhat helped, but my right eye is still dramatically stronger than my left.
Isaiah_6_8 t1_j1ym6kj wrote
I'm 40 and havent worn any eyeglasses up until about a year ago. My (general) doctor decided to do one of those eye chart exams during an annual physical and found that I was having a semi difficult time.. and so I was referred to the actual eye doctor. They found that I needed very minimal adjustments-- so much so, that the actual lenses look like I'm wearing fake/fashion glasses lol. Anyway... It was amazing how much clarity I was missing out on!
During the first few months of wearing them, I didn't notice too much of a difference with them off. But now, a year later, without them, it's very blurry. Did my brain do that favoring thing you talked about? instead of favoring a good eye over the bad eye, it's choosing glasses over no glasses?
Vanyeetus t1_j1yonmc wrote
From what I've gathered (lifelong glasses user) your brain can adjust for your crappy vision. It refines and fixes based on what it thinks should be there and is usually pretty good at it. When you get glasses and it no longer has to do that work (because the eye is transmitting a clearer image) it gets lazy and stops working on that refine and fix for the blurred vision. If you kept your glasses off long enough it may stay the same or you may adjust to it and think the blurs are normal because your brain is "erasing" them in real time based on what it knows something should look like.
The refine/ fix thing is a perfectly normal thing for the brain to do and it does it constantly in ways we mostly don't pay attention to (peripheral vision is a huge one for this) because it gets it right 99% of the time. The times it doesn't tend to produce things like shadow people or things that make you double-take and focus on an object because the fix the brain did was off enough for you to recognize it but focusing gave it more data to do it right.
tl;dr your brain is fuckin' weird and makes shit up constantly and when it doesn't have to do that it's a lazy fuck that sits on the couch and demands sugar, fat, and caffeine.
-WhatCouldGoWrong t1_j21rjce wrote
my eye doctor told me a story about an older dude in england. lived alone. his children came round now and then to make sure he was looking after hisself and his cupboards had food in them. for a decade or so this was the routine. one night he had a bad fall and during the course of his recovery and assessment if he could still live alone he went the doctors, they sent him to the eye doctors, the eye doctors concluded he was fully blind and had been for a long time
​
There was a bit of investigation into neglect from the children had they just let him bumble around this house fully blind for a few years but ultimately they concluded his brain had built an image of his house, the furniture, everything within the property from when he could still see stuff, so though he could not see, he could still see how it all was in his brain so he never seemed like he was blind to his children
​
I'd love to know if there's a link to that. It's a story that always stuck with me and made me wonder.
triskat35 t1_j20il9w wrote
Your tl;dr is hilarious but true!
DreadMCYT OP t1_j1xhwy5 wrote
How does the brain not paying attention to one eye work? Does the baby just go blind in that one eye?
AirborneRodent t1_j1xjct0 wrote
Depends on the semantics of "blind". The eye doesn't just completely turn off, but it will have severely decreased vision, and the person may only perceive stuff with it when the good eye is closed.
Brain science is still new and not fully understood, but there are groups of neurons in the brain called ocular dominance columns that light up when one eye or the other is stimulated. In most people there are equal numbers of ocular columns for each eye. But in brains that had a bad eye during infancy, most of the ocular columns will be linked to the good eye. In other words, the brain literally rewires itself to be essentially one-eyed.
DefinitelyNotA-Robot t1_j1y5h2p wrote
Yes. Normally, your brain takes two separate but similar images from your two eyes and fuses them together to make your "vision". When the two images aren't similar however, like if the picture from one eye is much blurrier or you have a lazy eye that's pointing in a different direction, they're too different for your brain to fuse together. Instead of confusing you with two dissimilar overlapping pictures, your brain says "well, this is probably the right one and it'll be good enough" about the good eye and literally just stops displaying the bad eye to you.
After a while, it stops even checking to see if the bad eye has something useful to display since it never ends up using it, and the pathway from that eyeball to your brain atrophies. All brains are plastic, meaning they can create new pathways, but babies brains are way more plastic than adults, so it's critical to correct this issue as soon as possible. You can try to fix it when someone's older, but you're unlikely to be as successful.
If you don't fix it in time, the person will literally stop being able to see out of that eye because the path that sends the image from the eye to the brain just doesn't work anymore. Nothing happened to the eye itself, but without that connection the image won't get to your brain for you to be able to see it. You'll mostly see out of just one eye when you have both eyes open although if you close your good eye you may still be able to see something out of the bad eye depending on how atrophied that pathway between the eye and brain are. However, you'll probably never be able to completely successfully fuse two images together, which can result in lifelong vision problems.
haddock420 t1_j1y4seh wrote
My eye doctor told me this is what happened to my left eye. My vision in my right eye is very good, but the vision in my left eye is terrible. If I close my right eye, I can only make out letters if they're several inches tall. Is there any way of correcting this as an adult?
AirborneRodent t1_j1y5fqo wrote
Sorry. The traditional textbook answer is that no, it's not possible after childhood.
However, there's a blurb on the wikipedia page that says that may be outdated knowledge. There is tentative evidence that it might be possible. If I were you, I'd look into the linked sources on that wiki page and talk to your doctor about your options.
haddock420 t1_j1y5n0u wrote
Thanks for the link. I'll check it out.
Euphoric_Software481 t1_j1yxfmt wrote
Hello, guy with lifelong vision impairment due to one of my eyes not being favoured by my brain since childhood, here. It sucks that I'll probably never know how normal people see the world.
Anxious-Debate t1_j201q2j wrote
This happened to me! I can close my left eye and nothing in my vision changes, but if I keep the left one open and close the right one, everything jumps to the side. It's funny to keep winking with my right side and watch everything jump back and forth. Eye doctors did try to correct it when I was younger with eye patches, but no luck. Though I think my right eye overcompensated and got worse as a result, as it now has a prescription literally double the strength of the left eye
Coffeeaddict444 t1_j205x7m wrote
This is the correct answer. To expand on it: You don't need a fancy machine. Lenses, including our corneas, work both ways. Therefore you can just shine a narrow beam of light into the eye, moving it across the eye serveral times (Skiascopy). If the beam moves across the retina in the opposite direction of the movement of the light, you know the focal point lies in front of the retina. If it moves across in the same direction as the beam, the focal point lies behind. Now you can just hold up test lenses and see with which lens the reflection of the beam of light stops moving, meaning the retina is in focus. This is basically the old school method of doing it, but is much easier explained by drawings or a video.
SKTwenty t1_j20hc7k wrote
Oh hey, I knew about the bad eye thing lol my right eye doesn't turn to the right. My peripheral is pretty strong but my body favors my left eye entirely
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