Great eyes, and SPOILER on ep 10 my3crichtons

[Cedric]

Hi friends! I'm not so well spoken in english, so I've been wondering... Exactly what does it mean when Crichton says that his eyes are better than "twenty-twenty"? Is it some kind of system you guys use, like from one to twenty, where twenty is max and you have perfect sight?

Another thing, have you ever thought of what the group would've been able to accomplish IF the future-Crichton would have stayed on Moya? What would have happened with them all? Any interesting.. fun, or just plain stupid ideas? I've been waiting to ask this question, :D hope you want share! and what if ancestral(?)-Crichton would've stayed? (he sure was swell! :love: )

PLEASE - DO NOT PUT FORTH ANY SPOILERS AFTER EP 10 IN YOUR IDEAS :love:

[Deadman]

"Twenty-twenty" means perfect eyesight. I'm not sure how the measurements work but "twenty-twenty" means you are not near-sighted nor far-sighted. Bettter than twenty-twenty I think is not really possible, but it is a human trait-----to say you are better than you are. Does that help?

[Cedric]

Aahh thanks, guessed it was something like that. Just wanted to know in greater detail.

[TalynLives]

http://science.howstuffworks.com/question126.htm

I'm not sure if it's directly related to near sightedness/far sightedness. As in I think it has more to do with the resolution of your retina than focus.

For example, I'm short-sighted but when I'm wearing my glasses I can see extremely fine levels of detail that many people I know can't.

[Nicola]

Hi friends! I'm not so well spoken in english, so I've been wondering... Exactly what does it mean when Crichton says that his eyes are better than "twenty-twenty"? Is it some kind of system you guys use, like from one to twenty, where twenty is max and you have perfect sight?

Another thing, have you ever thought of what the group would've been able to accomplish IF the future-Crichton would have stayed on Moya? What would have happened with them all? Any interesting.. fun, or just plain stupid ideas? I've been waiting to ask this question, :D hope you want share! and what if ancestral(?)-Crichton would've stayed? (he sure was swell! :love: )

PLEASE - DO NOT PUT FORTH ANY SPOILERS AFTER EP 10 IN YOUR IDEAS :love:

Future Crichton was a nasty version - he and Scorpius would have been best friends. Zhaan identified the flaws with Future Crichton in this exchange.

ZHAAN: You are not the John Crichton I know.
FUTURE CRICHTON: Zhaan... look at what's happened to me. How could I be?
ZHAAN: I wonder if you can also see what you have lost. Your logic may be firm but it is cold.

Scorpius and Future Crichton shared a cold, unemotional logic - and they were very similar.

What I liked the most was how Chiana connected so quickly and so completely with Ancestor Crichton. Chiana may be an impulsive and immature character - but her instincts are quite sound in this case.

[mjwillia]

What 20/20 vision means is this:
Normal acuity is measures using letters or symbols containing a 5 min/arc gap. This gap is about the width of a human thumb. Humans with normal acuity can see this gap at 20 feet away.

Why is 20 feet the “standard distance?” Because rays of light entering the eye from a source 20 feet away enters the eye in nice straight parallel lines. This is important because your eye does not have to “bend” these rays of light in order to focus them on the retina. It is the light entering at an angle that has to be actively focused by your eye in order to bring it to a nice point on your retina.

Here’s the problem: Some people have pointy corneas and/or longer than average eyeballs. The light rays entering at an angle for these people gets focused to a nice point out in the middle of the globe of the eyeball instead of on the retina. These people are “Myopic” or near-sighted. Some people have flat corneas and/or shorter than average eyeballs. The light rays entering at an angle for these people doesn’t have enough room/length to be focused anywhere inside the eyeball let alone on the retina. In fact, for this kind of problem the light (if it could but it can’t) would have to pass through the eyeball to come to a nice focused point somewhere in the back of your head. These people are “Hyperopic” or far-sighted.

20/20 acuity means at 20 feet you can see the 5 min/arc gap in the symbol.

People can have 20/15 or 20/10 acuity (usually younger people between 10 – 40 years of age). These people have better than average acuity. They have better than 20/20 vision. A person with 20/15 acuity can see a smaller than 5 min/arc gap at 20 feet but the average acuity person would have to be closer to see this gap ie. The average acuity person would have to be 5 feet closer or 15 feet away. A person with 20/10 vision can see an even smaller min/arc gap at 20 feet away while the average acuity person would have to get up to only 10 feet away to see the same gap.

The Airforce loves the people with better than average acuity. These folks aren’t Near-sighted or Farsighted they just were born with excellent visual resolution. They tend to lose some of this resolution with age…

[eleuthera]

Loved the explination! Thank you.

[mjwillia]

You are Welcome!

It makes sense that John would have better than 20/20 since he was/is a pilot. Pilot's don't have to be better than 20/20 but it does come in handy!

[Spedoinkel]

So, how do people develop worse sight? I don't think their eyes elongate or shorten. Do their cornea, and iris degrade?

[jerseygirl]

People tend to get more farsighted as they get older. That's because the eye loses the ability to change the shape of the lens to focus on near objects. That's why people over about 40 or so start wearing reading glasses.

[mjwillia]

Jerseygirl is right about people over 40 becoming more "farsighted." This is called Presbyopia. All humans become presbyopic as they age. What happens is: The lens inside your eye is made of a clear protein. It is constucted a lot like an onion. This "onion like lens" sits inside a sack that can stretch a lot but it does have it limits. The Lens continues to add new layers outer layers of protein which squeezes the inner layers closer together making the lens more dense and less crystal clear. The sack pretty much stretched all it can stretch by the time Women hit 42 years of age and Men hit 45 years of age. Why is this important? The lens in your eye does the "fine focusing" of objects. The lens will get fatter more like a balloon if your Iris relaxs just a bit. A fat lens can bend rays of light more and this helps you see thing close up. This is called "Accommodation." The lens will get thinner more like a dinner plate when the Iris tightens up. A thin lens can't bend light as much so you can only focus on things farther away. Once you are in your 40s and later you lose the ability to Accomodate because the lens is getting to dense with layers of protein and the sack can't stretch any more and so the lens slowly is forced to be more like a thick dinner plate and it can't take the shape of a baloon anymore.

You can become more Myopic or Hyperopic for other reasons too.

You can become more Myopic (near-sighted) for two reasons:
1. Your eyeball itself can elongate a little. Generally this only happens in rear cases. It's a genetic thing and some people's eyes can elongate to the point that their retina tears and they need surgery to save their sight.
2. Your cornea is super flexable and it changes shape a little all your life. That way some people will have anastigmatism for a few years then it goes away and then it comes back. People in their 20s often begin to wear glasses because their corneas become a little more pointy making them myopic. Pregnant women's corneas change a lot during their pregnancies and most doctors recomend not fitting a pregnant women with contact lenses until after she has her baby because the cornea most likely is going to change back once the baby is born changing the fit of the contact lens.

You can become more Hyperopic (far-sighted):
1. You lose Accomodation as explained above.
2. Your cornea can flatten more.

There is also a whole host of other things that can change your acuity. Cell death in the retina, clouding of the cornea, clouding of the lens, and even clouding of the vitreous gel in the globe part of your eye. Not to mention cell death in the brain where the impluses from your eye are sent and where these impluses are "read" by the brain the Ocipital Lobe.

[TalynLives]

Now there's a cheerful read :eek:

[mjwillia]

Yep - no one gets out of Life alive!

[Cedric]

Wow, didn't quite expect to get such a detailed explanation of my question :)
So I just have to ask, are you a doctor or something?

[mjwillia]

I have a Master's degree in "Blind Rehabilitation Teaching." This degree includes low vision testing. I then worked for an Ophthalmologist making artifical eyes and fitting contact lenses...

[eleuthera]

I am in the "lost accomodation" group. I went to the optometrist when I was about 43 to see why I couldn't see to thread a needle any more. I still hear her saying ..."As we age......." and me thinking "what ...me age...noooooooo" But as Woody Allen once observed "it sure beats the alternative." (or something along those line). Now I wear glasses to read and glasses to drive. But at least I can still watch Farscape without them!

Thanks again for the wonderful description of vision and the functioning of the eye.

[mjwillia]

Looking on the "bright side," Alcon a manuafacturer of contact lenses and Inner Ocular Lenses (IOL - these are the lenses inserted in your eye after cataract surgery) came out in 2004 with a bi-focal IOL. These new bi-focal IOLs are just beginning to catch on with the surgeons and offer independence from using reading glasses. On the down side, we have to wait until we have cataracts to get them. If you are interested in learning more about ophthalmology go to www.ophthalmologytimes.com and read all sorts of articles on all sorts of vision topics.