What is the Difference Between LASIK and PRK Laser Eye Surgery?

I perform roughly 50% LASIK and 50% PRK in my laser vision correction sub-specialty practice. In LASIK, a flap is created on the corneal surface before the excimer laser is applied. In PRK, no flap is made.

In LASIK laser eye surgery, a corneal flap is made and lifted from the surface of the cornea to provide access for the laser to sculpt in the new optical shape. At the conclusion of the procedure, the LASIK flap is re-positioned into place. The primary purpose of the flap is to provide very quick recovery by restoring the surface of the cornea.

For many patients, LASIK is not a good choice because the flap is contraindicated. For example, patients with very thin or weak corneas should not have a LASIK flap. Many of these patients who are unable to have LASIK can have PRK surgery instead and enjoy visual results every bit as good as LASIK. PRK surgery is essentially exactly like LASIK — except no flap is made. In fact, it is sometimes called “flapless LASIK.” Since the laser still needs access to the cornea, a different strategy than making a flap is used.

Every human cornea is covered by a microscopically thin skin layer called the epithelial layer. It is one of the fastest healing tissues in the human body. In PRK laser vision correction, a disc of this epithelial layer is removed to expose the underlying cornea, but no flap is made. The laser is then applied to the cornea and, rather than placing a LASIK flap back to cover the cornea, the skin simply is allowed to grow back instead. A clear, ultra-thin contact lens, called a “bandage contact lens” is placed over the eye immediately after surgery and stays there for about a week, after which time it is discarded. This bandage contact lens makes recovery more comfortable than it would otherwise be. It also protects the healing skin in the way a Band-Aid protects a scraped knee.

Recovery with PRK is slower than with LASIK. It typically takes the skin 4 days to cover the eye back over. For the final 48 hours or so of these four days, the eyes are burny, teary, irritated, and light sensitive — much like being around someone chopping onions. The vision typically is much improved once the irritation stops and the contact lenses are removed. Typically, though, the vision still is not perfect, however, as the new, fresh skin that has covered the eye is more irregular at first than it will be once it smooths out and you’ll be looking through this fresh, new skin. The vision remain improved — but not perfect — for several weeks after the bandage contact lenses are removed. Typically most patients feel they are close to the level of their glasses or contact lens vision by around one month after the bandage contacts are removed. The vision continues to “fine tune” for 3 to 6 more months, but by one month, most patients are already very impressed and satisfied with their vision. Most patients return to work one week after their PRK surgery.

Most researchers — including me — feel that the results of wavefront PRK and wavefront LASIK laser eye surgery ultimately are essentially the same, although it takes PRK longer to get there. In many cases, PRK is the more cautious choice, particularly in terms of preserving corneal biomechanics. In my practice, in which I do nothing but laser vision correction eye surgery as my specialty, I perform roughly 50% LASIK and 50% PRK. The decision to perform LASIK or PRK is one of the most important and involved ones we make at our consultation visit.

In my next blog, I’ll look at different PRK techniques for removing the epithelial layer.

What is the Difference Between LASIK and PRK Laser Eye Surgery?

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