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Ask Me Anything About Optometry/Eyes
Johan Halmén
Member #1,550
September 2001

You would have to define what "your perception" and "my perception" is before you imagine us switching them. Should we switch retinas? Or the nerves? Or any part of the brain? I'd imagine everyone of us has a certain distribution of the wavelengths for the three different cones and they just happen to be somewhat at red, green and blue. But I guess they differ a bit. I don't think switching retinas would actually mean that the red and green would switch places, like when switching the R and G lines in a component video cable. I've noticed that what people think as perfect grey on a monitor, I find a bit blueish. Because it's not "real grey" consisting of all wave lengths, but just a somewhat even mix of the R, G and B of the particular wavelength of that particular monitor, my set of cones and their corresponding wavelengths might differ a bit from the average.

The brains simply receive three different signals (plus the "luminosity" from the rods) and we learn to make sense out of it. I guess if retina transplantations would be possible, it would feel like slightly screwing around with the R, G and B curves in a graphic editor. Or even twisting the hue value a bit. You get slightly funny colours, but soon you get used to it. Like this:
{"name":"601576","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/8\/3\/8327ef03443868a08b548348c1935c04.jpg","w":300,"h":233,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/8\/3\/8327ef03443868a08b548348c1935c04"}601576{"name":"601577","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/9\/8\/98f4ca3cebc1afe8c95162d9c36d7b3f.jpg","w":300,"h":233,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/9\/8\/98f4ca3cebc1afe8c95162d9c36d7b3f"}601577

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Years of thorough research have revealed that the red "x" that closes a window, really isn't red, but white on red background.

Years of thorough research have revealed that what people find beautiful about the Mandelbrot set is not the set itself, but all the rest.

An Ly
Member #185
April 2000
avatar

The one where you have to read the numbers in the circles. My one eye only fails on the harder ones -- so it's not so bad.

Thats the ishihara. It is only used as a screening tool and so cannot be used to determine how "bad" an eye is at colour perception. Other tests are better. See if you can get yourself on an anomaloscope (http://www.neuronresearch.net/vision/files/newnagel.htm). This is the be all and end all of putting your colour vision on a scale.

Oh, question - is it true that the genes leading to colour blindness in men tend to lead to 4D colour perception in women? I definitely heard it somewhere, but last time I mentioned it to someone, they didn't think it was true. If it is true, it must be quite a curse; TV screens and the like would never live up to the real world.

I have no idea. At a guess, I don't think so? The color deficiency gene is recessive and is on the X chromosome and so if you're female, if you have one of these it would not show as the dominant (normal) gene will be there.

Obviously 2 recessive colour deficient genes on X chromosomes would mean the female has colour vision problems.

ReyBrujo said:

Is there anything that, long term, can damage eyesight, like listening to loud music can do to your eardrums?

Most common problem is UV exposure and for most of us it is from the sun. Get some sunnies (good ones which fit well) and wear them often, even on overcast days.

Quote:

Also, do wearing smoked (almost black, no idea how they are called in English, imagine sunglasses but not as black) lenses during night affect eyesight in the long term?

Not to my knowledge. Won't help with vision much though, but will help you look more like P.Diddy.

How do you know that what I've been taught to call "green" wouldn't be what you would call "red" if you could perceive what I see?

Doesn't really matter in reality as we both have a common object to look at and we both agree to call it the same thing.

The brains simply receive three different signals (plus the "luminosity" from the rods) and we learn to make sense out of it. I guess if retina transplantations would be possible, it would feel like slightly screwing around with the R, G and B curves in a graphic editor. Or even twisting the hue value a bit. You get slightly funny colours, but soon you get used to it

Also, the retina is not the only part of the visual system. Don't forget the visual pathways to the brain, and the media before the retina (cornea, lens, vitreous, pupil sizes). The brain's interpretation of what is on the retina is also important. There are also "ganglion cells" which gather information from groups of cones/rods which further complicates matters.

Normal colour sight is based on the RGB model, believe it or not. We have red, green and blue cones in the retina. Natural visible light has all wave lengths between 400 and 700 nm (correct me on the actual values) but our RGB cones get trigged only on three different wave lengths, kind of. So when we see a yellow wavelength, our red and green cones get triggered (they are not that picky, there are overlapping bandwidths for red and green cones). So it's not a big deal if we look at a monitor, which emits red and green together and not real yellow. Unless we have yellow cones in the retina and have learned to percept the real yellow wavelength as yellow. In that case the red-green on a monitor will look like something else.

There is a funny thing that colour deficient people do. Say you have 3 colours which are quite similar, but a normal person could differentiate them and say they are "different colours". A colour deficient person may say:

Colour 1 same as colour 2 (putting them side by side to compare)
COlour 2 same as colour 3

But Colour 1 and 3 are different when they compare them side by side.

Wierd eh?

ReyBrujo said:

I guess Matthew should give you a custom title because you have been pretty helpful around (^.^)

Can I have the title of "Eye Checker"?

Arthur Kalliokoski
Second in Command
February 2005
avatar

I noticed a weird illusion when I was a kid, it seems the rods that see bright objects have a quicker response time than the cones. If I'd move a flashlight sideways, it'd appear that the brightly lit shield thing would precede the part that was lit by ambient light only. Has anyone ever seen this before?

{"name":"601578","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/0\/8\/08a8b62811f820cdfe019b816bf2aad2.png","w":800,"h":600,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/0\/8\/08a8b62811f820cdfe019b816bf2aad2"}601578

They all watch too much MSNBC... they get ideas.

An Ly
Member #185
April 2000
avatar

I'm trying it with my pentorch and it doesn't seem to do what you're describing. How big is your torch, how fast are you moving it, is the end red like the picture and what is the background illumination like?

Arthur Kalliokoski
Second in Command
February 2005
avatar

It held two 'D' cells, the background illumination was way too dark to read but you could walk around without trouble (maybe like 3/4 full moon), the end was red and probably bright enough to read words right next to it, and I wasn't following it with my eye. E.g. I was looking at a spot on the ground and moving the flashlight around.

[EDIT]
I was probably moving it about 4 hand widths per second.

I'm trying it now with a single LED keychain with my finger over the end (looks red from the blood) and a regular flashlight with my hand on the end, I can't make it do this now either. I'll try again if I have to get up in the dark later after my eyes have adapted to darkness.

They all watch too much MSNBC... they get ideas.

Johan Halmén
Member #1,550
September 2001

I've seen the following illusion. A pendulum a is oscillating above an object b. Because of the two strings holding the bead, the oscillation is back and forth, no rotation. The viewer looks at the pendulum through a smoked glass screen, but there's a gap for either eye. The eye looking through the glass sees a darker image and therefore there's a slight delay in the perception. Which makes the bead rotate above the object. And when the viewer moves sideways to cover the other eye, the rotation reverses.
{"name":"601579","src":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/7\/4\/74ae3d9c24f05b41407227fd290de0d5.png","w":268,"h":321,"tn":"\/\/djungxnpq2nug.cloudfront.net\/image\/cache\/7\/4\/74ae3d9c24f05b41407227fd290de0d5"}601579601581

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Years of thorough research have revealed that the red "x" that closes a window, really isn't red, but white on red background.

Years of thorough research have revealed that what people find beautiful about the Mandelbrot set is not the set itself, but all the rest.

piccolo
Member #3,163
January 2003
avatar

I have Another question.

If i try and read anything on the bus. text books newspager ,subtitles i get very dizzy.

reading dose not seem to affect other people what makes then different then me.
what is this? Is it bad or good? and how do i fix it if bad?

wow
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i am who you are not am i

Vanneto
Member #8,643
May 2007

piccolo: its a common phenomenon. Many people get sick/dizzy if they read while in a moving vehicle.

An Ly: so, regarding strabismus. So it can be fixed/manager even if you are older than 8? I'm currently 18. Just want to know if its even worth trying. :P

In capitalist America bank robs you.

Thomas Fjellstrom
Member #476
June 2000
avatar

I'll try again if I have to get up in the dark later after my eyes have adapted to darkness.

The cells that have better dark vision work a lot slower. So I can see how the light part of the light will appear to move a little faster. Its just that after you've adjusted to the darkness most of your eyes detectors are tuned for low light, and will lag out compared to any that aren't.

--
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piccolo
Member #3,163
January 2003
avatar

Vanneto said:

piccolo: its a common phenomenon. Many people get sick/dizzy if they read while in a moving vehicle.

So dose this mean I'm weak or is this a side affect of being to strong in another area?

If its because i am weak let me know how to train my eyes so I'm not affected.

I have worn glasses from grade in primary school. Because i used to take a guys glasses in my class and try them on.

wow
-------------------------------
i am who you are not am i

bamccaig
Member #7,536
July 2006
avatar

piccolo said:

I have Another question.

If i try and read anything on the bus. text books newspager ,subtitles i get very dizzy.

reading dose not seem to affect other people what makes then different then me.
what is this? Is it bad or good? and how do i fix it if bad?

This is because your eyes are sending a different signal than the rest of your body. Your body is signaling to the brain that you're moving. Your eyes tell your brain that you're not moving because you're looking inside the bus, which moves with you, instead of outside which does not. I imagine that your brain can be trained to deal with this, but it's a natural response so you shouldn't feel bad about it. Your brain is basically confused and the natural response when that happens is to feel disoriented (i.e., dizzy). Many people actually feel sick because of this (it's called motion sickness).[1]

Thomas Fjellstrom
Member #476
June 2000
avatar

I only tend to get sick in a vehicle if I'm super hungry. Worse if I'm also reading.

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

Arvidsson
Member #4,603
May 2004
avatar

piccolo said:

If its because i am weak let me know how to train my eyes so I'm not affected.

Yes, your weakness is indeed shameful. The only solution is to read HARDER and LONGER until your body can't take it anymore so that you throw up. Rinse and repeat three times, then your body will learn to fear you because you are strong and thus the body will not dare to get dizzy ever again.

GullRaDriel
Member #3,861
September 2003
avatar

Hello An Ly.

I just have a few questions.
I do yearly visit to medicine-of-work to check if everything is OK, and last year I had a 12/10 near/far eyesight.
That year, on the same machine, even after trying two time, it looks like I now have a 13/10 eyesight.
Notice that I would not complain about gaining eyesight, I just want to hear some explanations on the topic.

Also, I want to have your point of view about things like "Dr NoName Eye Training Game" or so.

"Code is like shit - it only smells if it is not yours"
Allegro Wiki, full of examples and articles !!

ReyBrujo
Moderator
January 2001
avatar

piccolo, just read more and more until you get used to that. I can travel by bus, watching videos or reading, even when sitting opposite to the bus movement. However, got friends who can't handle that.

--
RB
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GullRaDriel
Member #3,861
September 2003
avatar

Just looking at my left and I see someone who can't read in a car.

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X-G
Member #856
December 2000
avatar

I'm pretty badly nearsighted (I don't remember the exact rating; -6 something, I think), and in my mid-twenties. I haven't had my eyesight checked in a while. How often should I do so, and/or get new glasses?

--
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GullRaDriel
Member #3,861
September 2003
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Don't give up that easy, An Ly ! :-p

"Code is like shit - it only smells if it is not yours"
Allegro Wiki, full of examples and articles !!

An Ly
Member #185
April 2000
avatar

piccolo said:

If i try and read anything on the bus. text books newspager ,subtitles i get very dizzy.

There are 2 main systems in the human body which affect balance. One is your visual system. If you see the ground below you and the sky above, probably means you're upright. This is a simple example but can be extrapolated to work with common objects (like the sun, buildings etc).

The other system is the semi circular canals in your ear. These canals are semi circular (hence the name) and you have 3 of them in different orientations. They contain fluid and when you move or adjust your posture, the change in the fluids tell your brain your orientation or movements.

If these 2 systems are telling the brain the same thing, then you're all good. If they are mismatched, the brain doesn't like it, sending pain signals (headaches).

When you're reading the 1st system says you're not moving. But in a car your semi circular canals say you are. This disparity causes your dizziness. Some people are more sensitive to others.

I haven't heard of ways this can be trained. However, from personal experience, I had to do last minute study on the rides to uni and the first few weeks I got dizzy. But due to my lack of studying early I had to persist. By the end of 1st semester I could read on the bus.

Some people tell me if you pull the book further from your face you can see the moving road in the periphery of your eye and this makes it better. No study I know of proves this though.

Vanneto said:

so, regarding strabismus. So it can be fixed/manager even if you are older than 8? I'm currently 18. Just want to know if its even worth trying

18yo is still ok. I would go for it if you really want to. Find a good optometrist who knows what they are doing. If you go to the wrong one you will be wasting your time and money.

When you do find one, follow their instructions. Do not deviate from it even a bit. The training schedule is devised to work for you and even over doing it is bad.

I've found that the most successful patients are the ones who really want to improve.

By the way, do you know what your VA is?

I do yearly visit to medicine-of-work to check if everything is OK, and last year I had a 12/10 near/far eyesight.
That year, on the same machine, even after trying two time, it looks like I now have a 13/10 eyesight.
Notice that I would not complain about gaining eyesight, I just want to hear some explanations on the topic.

I'm not sure if your system of measurement of eyesight is the same as in Australia. In Australia (and US/UK) the way we measure VA (visual acuity) is by reading letters. Then we give it a measurement:

e.g. 20/40, 6/6, 6/18 etc

Lets take 20/40. The first number (20) is the distance to the letter chart (20 ft). The 2nd number (40) is the distance the "normal" person can read it at.

This means 20/40 is not very good vision as the "normal" person can read it at 40ft but you can only read it at 20 ft.

This also means that 20/20 is "normal" vision.

In Australia we use the 6/6 system (metric system).

So I'm guessing 12/10 means your working distance is 12m/ft? Then 13/10 is 13m/ft?

It is an odd way of measuring VA as it means your working distance (distance to the chart) changed every year?

Anyways, VA only a small way to measure vision. Your VA reported is better than "normal" and so improvements which are better than "normal" usually come with being better at guessing (or working out letters) letters when it comes to reading the smaller print. If you practice reading tiny print at the distance, you can improve your VA in minutes.

Quote:

Also, I want to have your point of view about things like "Dr NoName Eye Training Game" or so.

Like on the DS? I haven't played them so I can't comment, sorry!

X-G said:

I'm pretty badly nearsighted (I don't remember the exact rating; -6 something, I think), and in my mid-twenties. I haven't had my eyesight checked in a while. How often should I do so, and/or get new glasses?

A checkup usually every 2 years is recommended but if you're eyes are changing rapidly then you'll need more regular checkups (maybe yearly).

You should get new glasses when your optometrist recommends it. I know it sounds like we're just trying to make you buy stuff. But if that is the case with your optometrist then you're going the to the wrong one.

How do you know if he/she is just trying to sell you stuff? You can't tell. But rapport helps. If you like the guy/girl then you're usually ok.

In Australia, the Optoms in the big chains (OPSM, Paris Miki etc) usually get a cut of the products sold. Sometimes that can sway their opinion.

But then again, optoms who own independant practices take the whole profit.

Discuss.

The cells that have better dark vision work a lot slower. So I can see how the light part of the light will appear to move a little faster. Its just that after you've adjusted to the darkness most of your eyes detectors are tuned for low light, and will lag out compared to any that aren't.

Can you see the red colour with the experiment? If so then you're also using your cones which are the "detectors" which work in bright light. The detectors tuned for low light (rods) wouldn't see the red colour.

Don't give up that easy, An Ly ! :-p

Give up what?

Thomas Fjellstrom
Member #476
June 2000
avatar

An Ly said:

Can you see the red colour with the experiment? If so then you're also using your cones which are the "detectors" which work in bright light. The detectors tuned for low light (rods) wouldn't see the red colour.

I haven't tried, but I assume thats why you'd get the light part moving faster than the dark part, normal light detectors (cones?) are faster than the rods (no?).

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

Arthur Kalliokoski
Second in Command
February 2005
avatar

An Ly said:

Can you see the red colour with the experiment?

If you're talking about my flashlight story, yes, the red part was quite a bit brighter than necessary to see it was red. I can't seem to remember to try it again when I wake up groggily in the middle of the night to use the bathroom.

Since others here say that it's been known that cones respond slower I'll drop it.

They all watch too much MSNBC... they get ideas.

GullRaDriel
Member #3,861
September 2003
avatar

Give up on responding ;-)

In France the system is as following (from what I know):

  • 10/10 is normal vision

  • Fighters pilots must have at least 12/10, the average have 14/10

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Dario ff
Member #10,065
August 2008
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Based on how many consults you've answered here, how much money would you've earned already?

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GullRaDriel
Member #3,861
September 2003
avatar

My bet: A bunch !! :-p

"Code is like shit - it only smells if it is not yours"
Allegro Wiki, full of examples and articles !!

BAF
Member #2,981
December 2002
avatar

10/10 is normal, but average is 14/10? Wouldn't that make 14/10 normal? You Europeans make my head hurt.



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