Presbyopia is a progressive loss of our capacity to focus clearly at near. It is a normal process related to aging, and eventually it affects everyone. Although we start losing this function, called accommodation, at an early age, in most cases it becomes rapidly manifest during our early to mid-40s.
Monovision is a term used to describe an induced refractive disbalance between the two eyes. One eye, generally the dominant eye, is fine tuned to see well at a distance, and the other eye is left slightly nearsighted. Although it sounds unnatural, the vast majority of patients like monovision. The key for successful monovision is determining whether or not the patient likes it, prior to doing surgery. This is usually achieved by conducting a contact lens trial. Monovision can be achieved with glasses, contact lenses, laser surgery, or implant surgery.