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’.
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’.