People usually ask me if they're a candidate for refractive surgery. Most surgeons usually want the patient to be at least 21 years old although I have seen some surgeons perform surgery with the patient at 18 years old.
A prime consideration for performing surgery at any age is if the eyes are changing. If they are, usually the surgeon will not perform surgery no matter what the age is.
A third and very important consideration are the ages between 35 and 42. This is a critical age because around this time the focusing system of the eyes is changing. Let's say you perform a surgery at 39 years of age. The patient should be able to see both distance and near. However, as the patient gets into the early 40's, the patient will not be able to see as well close up and will probably need reading glasses.
If the patient is in their mid 40's or older, they already know they can't focus through the distance prescription . In this case they'll either have surgery where one eye's for reading and one eye's for distance or they'll need reading glasses for up close if both eyes are corrected for distance.
The above surgeries only pertains to corneal surgery. If the older patient elects, they can have surgery where a multifocal lens is implanted into the eye and they can see far and near.