Laser eye surgery specialist David R. Shapiro, M.D. is one of the nation's leading authorities on refractive eye surgery.
A common myth I often hear is that having LASIK causes --or accelerates -- the need for reading glasses. This is not the case! The need for reading glasses is called "presbyopia" and it occurs as a natural result of the aging process -- whether or not you have had LASIK.
Ophthalmologists still debate the actual cause of presbyopia. The best explanation seems to be that the natural lens of the eye, which is located inside the eye behind the pupil, becomes stiffer with age. The job of the lens is to flex or bulge to provide good close vision and then to relax for distance vision. A young person is constantly flexing and then relaxing their lens as they look up close and then look back out to distance. This flexing and relaxing is an unconscious and effortless process in people under age 40 with healthy eyes. After age 40, however, the lens becomes stiffer and stiffer with age -- all the way up until age 60 or so, at which time the lens has become completely stiff. For this reason, it is natural for healthy eyes to notice an increasing loss of close vision -- and an increasing need for reading glasses or "cheaters" -- beginning after age 40.
LASIK does not cause this process. In fact, LASIK surgery is performed on the cornea -- the outter surface of the eye. The lens is not touched during LASIK surgery. For this reason, LASIK does not make presbyopia better and LASIK does not make presbyopia worse.
It is true that a nearsighted person after age 40 still can take their glasses or contacts off and see up close without reading glasses. This is because, with glasses or contacts off, their natural nearsightedness makes the distance poor and the close sharp. In technical terms, nearsighted people have a close point of relaxed focus so they do not need to flex their lens to see up close, so presbyopia will not affect their near vision with their glasses or contacts off. The problem, of course, is that nearsighted people can't see well in the distance without their glasses or contacts on, so they end up having to wear their glasses or contacts (unless they undergo LASIK) and therefore end up needing bifocals in their glasses or reading glasses over their contacts.
While LASIK does not cause presbyopia, there are strategies for addressing presbyopia when LASIK is performed. One option is to use LASIK to set both eyes perfectly for the distance. This is called "stereo vision" and provides the best possible distance vision, the best possible night vision, and the best possible depth perception using LASIK. With stereo vision, a person will need reading glasses at an age appropriate level after LASIK. A 30 year old having LASIK for stereo vision would not need reading glasses, but a 50 year old would.
Another option is called full, or classical, monovision in which the dominant eye is set for perfect distance vision and the non-dominant eye is set for close, reading vision. Monovision LASIK does provide good near and far vision, but the quality of the distance vision -- and particularly the quality of the night or low light vision -- is not as good as with LASIK for stereo vision.
A third option is called "blended" vision, or mini-monovision. This is a very popular option in my practice for patients who are over 45 years old. With blended vision, the dominant eye is set for distance and the non-dominiant eye is set for the midrange, rather than the close. With blended vision LASIK, the two eyes work together better as a team than they do with full monovision. The distance vision and the night vision are all typically much better than with full monovision LASIK. The distance vision is not quite as good as with stereo vision LASIK, but many patients find the slight trade off in distance is worth it to them to open up their mid range vision. The goal of blended vision is not necessarily to be free of reading glasses for small things. Instead,the goal is to be able to still use a cell phone or write a check without glasses, while still enjoying very good distance vision -- all in a presbyopic age range of over 45 years old. Patients with LASIK for blended vision will still, of course, continue to age and their presbyopia will continue to worsen (which will continue to make their close vision worse), but, for any given age, they will always be "ahead of the game" by having blended vision compared to the level of mid range vision they would have had LASIK for stereo vision.
Several researchers are now working on "PresbyLASIK." PresbyLASIK is a complex multifocal shape etched into the cornea by the laser during LASIK which is designed to make some of the cornea focus for distance and some of the cornea simultaneously focus for close. The results are mixed at this point and this procedure does not have FDA approval.
In another blog, I'll talk about future technologies that may some day help treat presbyopia without the use of blended vision or monovision. It is not clear, however, that these technologies will actually be better than blended vision or monovision. In the end, blended vision in particular will likely remain a very viable option for the majority of LASIK patients confronting presbyopia.