Most normally sighted patients require readers in their mid-forties. This is caused by the normal weakening of the focusing muscles of the eye, known as presbyopia, which usually starts around the age of 40—45. This condition occurs with or without LASIK. Those patients who currently have bifocals will still need reading glasses after the surgery unless they opt for a treatment plan called monovision, wherein one eye is corrected for distance and the other for near vision.