Multifocal LASIK for clear vision at all distances

A common sense is that presbyopia is evitable as the eyes age. Currently there is another solution named multifocal LASIK (presbyLASIK) for the large presbyopic population, complementing those traditional approaches, e.g. multifocal eyeglasses, multifocal contact lenses and artificial lenses. Although multifocal LASIK has not received FDA approval in U.S., clinical trials show that it will eventually become an advanced type of laser vision correction.

Multifocal LASIK differs from all of the other presbyopia solutions

Presbyopic patients have less flexible eyes which are unable to focus properly at all distances. Conventional LASIK only provides farsightedness or nearsightedness correction by reshaping the cornea and restores the ability to focus at near or far range. Regular LASIK and monovision LASIK both work in this way. In contrast, multifocal LASIK performs in a way that is quite different from all of the existing presbyopia solutions, e.g. multifocal contact lenses and eyeglasses, reading eyeglasses and even monovision lenses.

The principle and effect of multifocal LASIK surgery

Multifocal LASIK uses an excimer laser to reshape the cornea into different zones, creating several powers for near, far and intermediate vision respectively. The way of corneal reshaping is similar to that of regular LASIK and PRK. But this new procedure makes the cornea have several visual zones. The eyes perform different vision tasks through the three vision zones, similarly as multifocal lenses do. One advantage of multifocal LASIK over contact lenses or eyeglasses is that its multifocal vision outcome is fixed and usually permanent. Thus presbyopic patients are able to perform visual tasks involving any vision zones. More exactly, they are no longer presbyopic.

Different ways to arrange visual zones during presbyLASIK

PresbyLASIK has different variations according to the partition of vision zones. Some refractive surgeons suggest that the central part of the cornea should be shaped to provide distance vision and the surrounding corneal tissue is designated for intermediate and near vision. But there are still other surgeons arguing that a central cornea shaped for near vision can provide a stronger correction for reading and other near vision tasks. In fact, multifocal artificial contact lenses also have different designs, differing in power arrangement on the lens.

Different versions of monovision presbyLASIK

Applied into one eye only, presbyLASIK can enhance distance vision or near vision as desired. For instance, carpenters and dentists can get more near vision from multifocal LASIK. Monovision with presbyLASIK can also be combined with wavefront LASIK. Like other versions of monovision, presbyLASIK with modified monovision requires prior tests to determine whether the patient can adapt to monovision visual effect. This version of modified monovision will not affect depth perception at most distances. In rare conditions, patients may require the surgeon to reverse a presbyLASIK procedure. This problem of presbyLASIK under clinical trials affects to some extent its approval by FDA.

Potential disappointing outcomes after presbyLASIK

Clinical studies of presbyLASIK have shown positive initial results. Most of the patients can get 20/25 uncorrected visual acuity and get rid of eyeglasses. In contrast, multifocal LASIK will possibly bring disappointing results, e.g. blurry distance vision, reduced contrast sensitivity and night halos. Patients should also be clear that visual outcomes from presbyLASIK are sometimes not permanent. In this case, surgical enhancement will be needed. A worse case is that cataracts may develop after multifocal LASIK surgery, which requires more complex and challenging cataract surgery.