Does Lasik Cure Presbyopia?
No. LASIK does not cure Presbyopia.
LASIK is primarily for myopia (near-sightedness) and to a large extent astigmatism -in other words distance vision problems. Myopic people have their default focal point up close, not out at a distance like normal. LASIK fixes this by reshaping the cornea of the eye, not its lens.
In the normal eye, the default, relaxed lens shape is set for distance vision. When we bring our attention in to focus up close, we have to actually change the anatomy of the internal eye (although we are not aware of this) by using a muscle to squeeze the natural lens and so change its shape. This is called "accommodation." As we age, we lose our accommodation as the natural lens slowly gets more dense and less flexible. Presbyopia (which people call "farsightedness") is this increasing resistance of the natural lens to being squeezed into a shape suitable for seeing up close. Eventually the progressive loss of accommodation gets bad enough you need reading glasses to magnify things up close!
LASIK does nothing to change this. So why do you hear about people over 45 having LASIK and they can read? Two reasons:
- There is a second type of "farsightedness," much less common than presbyopia or myopia, called Hyperopia which can affect both near and distance vision. Being a distance vision problem, hyperopia can be treated with LASIK -although it tends to wear off in a way that myopic LASIK doesn't. But hyperopic people still get presbyopia so hyperopic LASIK isn't really all that great for up close vision.
- Nearsighted people can already see up close without accommodating. So when a nearsighted patient wants to have LASIK, just under-correct one eye: The residual myopia lets you read -but at the expense of full distance vision in that eye. And you can do this even in people with no myopia -LASIK can be used to deliberately over-correct and make an eye a little myopic. Now it can read without having to accommodate! But once again, this is at the expense of the distance vision in that eye. This approach is usually called "monovision" where "one eye sees off at a distance and the other eye sees up close."
Monovision is a very useful strategy to deal with the loss of near vision due to the age-related loss of accommodation, i.e. presbyopia. But it is more of an "end run around" it than an actual cure for presbyopia. Not everybody can tolerate the difference between the two eyes with monovision -so be sure to test it out with contact lenses and make sure of this before having monovision LASIK!
J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic
