LASIK Basics

The term LASIK is an acronym for Laser Assisted In-situ Keratomileusis. This procedure has corrected the refractive error of millions of people around the world. In fact, over a million people each year undergo LASIK in the United States alone. It is the second most commonly performed surgical procedure in the U.S., being second only to cataract surgery.

LASIK works well for most types and degrees of refractive error (myopia, hyperopia, and astigmatism), however, it certainly has its limitations as all procedures do! Most refractive surgeons would probably agree that LASIK works very well or extremely well in myopes with refractive errors up to about –5.00 or –6.0 diopters. At approximately –6.0 to –8.0 diopters of myopia, LASIK works well but poses a greater risk of reduced contrast sensitivity and night vision aberrations (I’ll review this in detail shortly). I believe that the majority of refractive surgeons do not recommend LASIK when myopia is greater than –9.0 or –10.0 diopters and above due to high risk of reduced contrast sensitivity and night vision aberrations.

For the hyperope (farsighted), LASIK works quite well up to approximately +3.0 or +4.0 diopters, however, this number is certainly debatable even among the most distinguished refractive surgeons. Again, I believe most refractive surgeons would agree that LASIK in the hyperopic patient has never shown as spectacular results as in the myopic (nearsighted) patient. This is because of the inherent relative ease of flattening the central cornea (as is the case in the myope) versus the inherent difficulty in steepening the central cornea (as must occur in the hyperope). However, the addition of tracking devices, which track the movement of the pupil during the procedure, and wavefront technology (see Chapter Nine), have certainly improved the outcomes of hyperopic LASIK. A number of refractive surgeons have begun to recommend conductive keratoplasty in hyperopes with refractive errors between approximately +0.5 and +2.5 diopters and they utilize LASIK for hyperopic refractive errors greater than +2.5 in patients under forty, and some refractive surgeons recommend clear lens replacement (Chapter 13) for patients over forty because this group already has presbyopia. This has considerable merit and I’ll refer the reader to Chapter 11 and 13 for more on CK or conductive keratoplasty and clear lens replacement (CLR), respectively.

LASIK combines the sophisticated precision of the excimer laser to reshape the cornea with a protective flap, the latter of which is created by either a mechanical microkeratome or a second type of laser known as the femtosecond laser (this procedure is known as “IntraLASIK”, which I’ll review in detail in this chapter). Let’s take a look next at the indications for LASIK, the pre-operative evaluation, and then the procedure itself.