Presbyopia is a term that is used when a person develops difficulty in seeing up close. It is related to the use of eye muscles to reshape the natural lens of the eye to achieve accommodation. Accommodation is a when the focusing power of the lens is increased and allows a person to see images up close.

The accommodative power decreases throughout life and eventually a person will need a positive power lens to improve the near vision. These lenses are often called "cheaters". The need for these glasses is dependent upon a person's eyeglass prescription. A nearsighted or myopic person can often decrease the need for reading glasses by taking off his/her distance glasses.

Why is this? Well, a nearsighted or myopic person has a location up close that they can see clearly without glasses. In mathematical terms it is 1/(the eyeglass prescripton) in meters. In optical terms is the near focal point of the eye.

For many people, the loss of near vision is a frustrating experience and they seek laser vision correction for treatment. In eyeglasses, they have an option of a bifocal style lens. However, this is not possible for laser vision correction. At this time a bifocal laser treatment cannot be applied to the cornea; the tissue that undergoes the laser treatment.

What can be done? The laser can create blended or monovision. In this scenario, one eye is corrected for distance and one eye is corrected for near. The eye that is corrected for near is made intentionally myopic or nearsighted. Once this occurs the patient will function in that eye like a nearsighted person. There will be a focal point at near where the vision is clear without glasses.

The reason this is called blended vision is because the eyes work together. One eye is more dominant for distance and one eye is more dominant for near. But both eyes has some functional vision at distance and near, although each eye dominates in one area.

For many people, this is a satisfactory experience. There are many contact lens users who wear monovision contact lenses. When considering monovision laser vision correction it is important to undergo a contact lens trial. If you are unsuccessful in a contact lens trial, I would not recommend monovision laser vision correction.

If you a successful in a contact lens trial, its important to know that the monovision correction that is appropriate at the time of surgery, many not be the same correction 3-4 years later. This is because the muscles continue to fatigue and accommodation continues to worsen even after the laser vision correction. A healthy outlook is being happy with being glasses free the majority of the time. If you would only be happy with 100% glasses free for the rest of your life, then I don't think you'll be satisfied with monovision.