comment by aubrey ·
2014-03-20T12:51:12.139Z · LW(p) · GW(p)
Laser eye surgery (LASIK) is being suggested by several people on LessWrong, who suggest it is a costly procedure that has high likelihood to improve your life. I do not think this is a good trade-off across a life time, because presbyopia.
Almost all humans experience presbyopia. This is age-related deterioration in the ability of the eye to adjust focus. In history, the biggest effect for most people is reduced ability to read, but now it also is affecting the ability to use computers.
If you have myopia (short sight), you can not see distant objects without distance glasses. However, myopia means that you will retain the ability to focus at close distance for longer as presbyopia develops.
So LASIK surgery is not only trading money for better distance vision: if it works, you get better distance vision but also you get worse close vision as presbyopia develops.
How long will you live in each condition?
According to last year's survey, the mean age is 27.4 (stdev 8.5). Presbyopia usually develops from age 40. Let us disregard the possibility of uploading because the mean date for the singularity is 2150. Life expectancy for a 27-year-old US male is 50 years. This is likely an underestimate. It is a period life expectancy, not a cohort life expectancy, and we do expect future improvements in longevity. It is, too, a population average. LessWrongers are smarter and better educated than average, which is associated with longer life. We will nonetheless use it for illustration.
So, very roughly, the trade for an average LessWronger considering LASIK is reduced need for glasses for 13 years against increased need for glasses for 37 years, or longer. Also, I guess that most LessWrongers with myopia spend much more time reading and using computers than doing tasks that require distance vision. I also guess they value those activities more.
Therefore this does not seem a good trade to me even if it were free of cost and risk.
Have I made a mistake? Has anyone more data? I know old people with presbyopia and I know young people with LASIK but I do not know anyone who has both. I guess some people on LessWrong have LASIK, but very few or no people have presbyopia, so I expect no people here with both. I guess that in universities there are faculty members who have both so I will ask on my next visits. Sometimes it seems even that all faculty members have myopia!
Replies from: Lumifer, wadavis
↑ comment by Lumifer ·
2014-03-20T14:40:53.636Z · LW(p) · GW(p)
The need for glasses is a binary variable -- either you need them or you don't.
Someone with presbyopia always needs glasses because he can't focus both near and far. It doesn't matter whether that person started with good eyesight, or with myopia, or had myopia corrected by Lasik -- he will need glasses.
You seem to think that presbyopia "corrects" myopia, that is not so. In geometric terms myopia "translates", shifts your zone of focus closer to you so that it doesn't include infinity any more. But presbyopia narrows your zone of focus, contracts it. You don't get far vision back by overlaying myopia with presbyopia.
Replies from: aubrey
↑ comment by aubrey ·
2014-04-27T16:26:32.429Z · LW(p) · GW(p)
Sorry, I was not clear. I do not think that presbyopia corrects myopia. It even makes it worse at distance. But at close myopia can offset the effect of presbyopia.
As presbyopia narrows your zone of focus, you can not focus as close as previously. If you have myopia, you can focus at much closer distances than people with normal vision. Before presbyopia, this is not much use. When presbyopia develops, you have more close vision to spare, and can still read a book or a computer screen when people with normal vision would need reading glasses.
I will give a simplified example. A person has mild myopia, and needs a correction to focus at infinity, of strength -2.50 dioptres. They have successful LASIK surgery which gives them normal vision. They develop severe presbyopia, and require a correction of +2.50 dioptres to be able to focus at a comfortable reading distance. They now need reading glasses. If they had not had LASIK surgery they would need distance glasses but would not need reading glasses. They can gain the correction of +2.50 dioptres by taking off their distance glasses.
This is why I say, "[with successful LASIK] you get better distance vision but also you get worse close vision as presbyopia develops.". What is more important may vary from person to person.
I have spoken to an optician about this, and she was mostly confirming this. This is only N=1 argument from authority though! She agreed of course that people with myopia and presbyopia can get good close vision by taking off their distance glasses. They do not need reading glasses, unless they wear contact lenses or have had LASIK. However, I must say that she did not not think that this would be a reason for most young people to not have LASIK. She said would certainly not advise LASIK for people with presbyopia or who would likely have it soon. She said also that people who wear contact lenses for myopia who get presbyopia, she will suggest under-correction in one eye, so that they have good distance vision in one eye and good close vision in the other.
Need for glasses is not a binary variable. It has more states than that. It must at least include 'need distance glasses' and 'need reading glasses'.
↑ comment by wadavis ·
2014-03-24T16:37:58.808Z · LW(p) · GW(p)
Please keep us updated on your findings and decisions.
I'm also looking at a cost-benefit of LASIK and watching the reports on early adopters. High chance of an improved quality of life versus a small chance of significantly reduced quality of life. So this is how risk aversion feels like from the inside.
Replies from: aubrey
↑ comment by aubrey ·
2014-04-27T16:31:08.702Z · LW(p) · GW(p)
I have spoken to an optician as in reply to other message in this thread.
I have also asked at a computer science department in a European university. It was funny! Everybody in the department except some grad students had myopia. Many of the older faculty also had myopia. But nobody had LASIK. Sorry I did not count properly. My visit was for other reason. However, I can say the modal mode of vision correction was glasses for distance vision and taken off for reading or computers. There were also some people with varifocal glasses. There were also some people with contact lenses for distance vision and reading glasses for reading or computers.