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cataracts, bandpass filters

It's time for me to get cataract surgery. I think I'll go for the fixed-focal-length lenses, maybe with astig correction.

I've always been nearsighted, which suits me fine, since I read a lot, compute a lot, and work with tiny parts on PC boards. I can wear glasses to drive or ski or whatever.

So, what should the focal lengths be? I've noticed that two eyes have a lot better resolution than one, even if one isn't well focussed. Brains integrate the images somehow. Some people go for one eye close-focussed, and one at distance, so they don't use glasses at all, but I have another idea:

Focus one eye really close, like 10" maybe, and the other at computer distance, 20" maybe. Ideally, that will give me good resolution from, say, 8 to 24 inches.

Something like this:

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There would be a box that defines a minimum resolution over some range of distances. This is starting to look a lot like a Chebychev bandpass filter, and I guess the math is similar. I could also get a flat Butterworth looking curve if I moved the peaks closer together, but that would reduce the working range.

The complications are:

Pupil size changes with illumination, so the two peaks get narrower in dim light.

I don't know how well a brain combines two inputs; probably better than just summing amplitudes. So the peaks could be farther apart than simple math suggests.

And, of course, I have to convince the doctor that I'm not crazy.

Reply to
John Larkin
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Yeah, I sort of felt that I'd rather wear glasses than have the artifacts of the coaxial lens things.

It is a crap shoot. I guess one could have it re-done if things really don't work out. Or make some custom glasses to simulate the implants, wear them for a month or two and see how they feel.

That's what I'm used to. I work close-up most of the time, and only drive a couple hours a week.

There are some new lenses that hook into your focussing muscles and restore adaptive focussing. I don't know if they are ready for prime time.

Reply to
John Larkin

Welcome to old age. Beware, they can cloud over suddenly, and you can't see... don't panic... a simple laser "dusting" fixes them.

I know people who have chosen to near/far option. They're not as happy as I... I chose 20/20 and Speert "clics" readers.

But then I tend toward driving at 110+, and need good depth perception

...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

They leave a membrane after they take out the old lens. This, in some people, gets cloudy. As you pointed out they use a laser to, I guess to vaporize it, and remove it. My mother opted for the 20/20. She does fine with close or far. She's

86 so I'm not entirely convinced. But the Opthamologist says she couldn't be better.

Cheers

Reply to
Martin Riddle

They had those lense for probably the last 10 years. It's really the Risk involved that determines if you can use them. Regular implants are routine. There is still risk, but it is managable. You only have two eyes you know.

Cheers

Reply to
Martin Riddle

Good luck with that... ;^J

But seriously, do you really want to optimize your vision for close work at the expense of vision for distance? That would mean you have to wear glasses to walk around, to drive to do most of the things people take for granted. If the doctors don't have any experience with this, you really won't have any way of knowing what your life will be like with this "optimization".

If I could divide my vision into three ranges with just one being near correct, I would pick distance as the vision with no glasses and then wear bifocals for computer/very close up work. In fact, that is what I'm doing now except I really need trifocals, but my distance vision is the best and I look over the glasses for that.

Rick

Reply to
rickman

It seems to be overrated. I think I won't bother getting any.

Sylvia.

Reply to
Sylvia Else
[...]

Ha ha, must try that!

--

John Devereux
Reply to
John Devereux

With something as important as vision, I'd not take a crap shoot. Custom glasses/contacts to try it out sounds prudent.

Reply to
mike

It goes in for inertia sales. You find you end up with rather more than you bargained for.

--
Bill Sloman, now 70 in Sydney
Reply to
Bill Sloman

The alternative is worse.

Reply to
krw

When/if the alternative becomes less worse, we generally have a choice we can make.

Reply to
Spehro Pefhany

I have the theory that you only age when you're awake. So sleep a lot.

Reply to
John Larkin

Lots of people die in their sleep. Some, without a pillow over their face.

Reply to
Michael A. Terrell

Actually, _excess_ sleep shortens your life-span. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| Phoenix, Arizona  85048    Skype: Contacts Only  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

heir

yeh, I read some study with something like 1mill people over 6 years death rate was lover for those who slept 7hours than those who slept 9 hours. Those with insomnia ~3-5 hours lived longer than the rest and taking a sleeping pill every night was nearly as bad as smoking a pack of cigarettes a day

-Lasse

Reply to
langwadt

If true, I'm sure there is a horse/cart issue here.

I'd have to see a reference to believe this one. Insomnia is a symptom that something's wrong.

Some are really nasty stuff (*very* addictive, even ones that claim not to be) so it's not surprising, though I've also heard that missing an hour's sleep (seven vs. eight) over a week is the equivalent of a BAC of .08 (legal limit), too. Lotsa stories about this stuff.

Reply to
krw

You have to wonder about this kind of study- they would have to carefully eliminate other effects to show evidence of causality.

For example, long sleep times might be a sign of slight depression, but not sufficiently profound to be clinically diagnosed as such. It is still potentially useful information, as it might point to something else that is wrong and treatable.

Reply to
Spehro Pefhany

Then I should live forever. :(

Reply to
Michael A. Terrell

Yeah, I'd advise some sort of simulation/testing before surgery.

For some people, there is a tight binding between eye focus, and eye convergence... the brain seems to have a very strong association between the "aim the eyeballs and lines of sight inwards" and "focus close" processes. For people like this (me included), "mixing" far-focus and inwards convergence, or near-focus and parallel lines of sight, can be distinctly difficult and uncomfortable... it seems to lead to eyestrain. I find some 3D movies and etc. to be difficult to watch, for this reason.

For other people, the focus / convergence systems seem to be less tightly bound - more independent.

As far as I can tell, this is an innate (and possibly inherited) difference between individuals.

What I'd be concerned about, with your "split focus distance" approach, would be that you might always find your eyes straining to achieve different focuses, leading to eyestrain and fatigue. One eye would always have a focus/convergence mismatch, relative to the other.

So, try it out first with corrective lenses (if you can) and see if it's a comfortable and non-fatiguing arrangement for you.

--
Dave Platt                                    AE6EO 
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior 
  I do _not_ wish to receive unsolicited commercial email, and I will 
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Reply to
Dave Platt

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