I have had 2 LASIK procedures already (original and one enhancement). Several years since my LASIK enhancement surgery. My right eye has 0.75 of astigmatism. The doctor said he doesn't recommend I do PRK but would do it if I requested. However, he told me PRK is a one time procedure and if I'm not satisfied with the result, I wouldn't be able to do it again. Is this true? If I get PRK now (I'm in my mid 30's), can I do it again (a 2nd time) when I'm in my 50's to treat presbyopia?