PRK / LASIK ~ LASIK, PRK, laser vision correction, eye care, hyperopia - farsightedness, myopia - nearsightedness, astigmatism and excimer laser information.

COMPARING LASIK TO PRK

PRK, or photorefractive keratectomy, is a refractive surgery technique which reshapes the surface of the cornea, while LASIK, or laser in situ keratomileusis, reshapes the inner layers of the cornea. Both procedures work incredibly well to correct mild and moderate degrees of nearsightedness, farsightedness, and astigmatism.

The differences between LASIK and PRK become apparent when comparing the speed, comfort or visual recovery results and risks involved in treating very nearsighted patients. It must be understood that final visual results are a combination of the laser procedure itself and the patient's own healing pattern. This is the simple answer as to why everyone does not achieve a perfect result with this amount of precision involved; quite simply, everyone heals in their own imprecise way.

Therefore when treating severe degrees of myopia where more healing is required, there is more variability in results and more risk of abnormal healing in the form of haze or scarring. It does not matter which laser or technique the surgeon uses or how experienced the surgeon is, scarring affecting vision will unfortunately occur in some patients. The inner layers of the cornea are far less likely to react and rarely produce haze or scar tissue, making LASIK a more ideal procedure for treating severe myopia.

It is this advantage of healing combined with the precision of the excimer laser that has made LASIK a highly successful refractive surgical procedure.

Although LASIK is a more complex procedure involving more technical skill, more staff/surgeon training, and more equipment, it enables the surgeon to treat the inner layers of the cornea, thus the risk of scarring is substantially reduced by a factor of 10 or 20.

LASIK, when performed by an experienced surgeon, takes about 15 to 20 minutes to complete, about the length of time of PRK. Both PRK and LASIK procedures are completely painless. Patients are always amazed at the ease of both these procedures because of their speed and comfort. In both procedures only topical anesthetic drops are used to numb the eye for the procedures. An eyelid holder is inserted to prevent blinking while the drops eliminate the reflex to blink.

In the PRK procedure, the protective epithelial layer is first removed, revealing the next layer known as Bowman's layer. Epithelial removal can be performed mechanically or with the laser.

With LASIK, the epithelial layer is left intact, allowing for not only faster visual recovery but improved comfort and safety. With PRK, the surface of the cornea is lasered with the patient's prescription, removing Bowman's layer.

With LASIK, is it important to have an adequate amount of tissue removal for full correction, as excessive tissue can result in severe corneal instability. For patients with thin cornea or those with normal thickness cornea with disproportionately high prescriptions, it is best to treat a large area (6.0mm or more) and be left with some residual myopia rather than be fully treated with a small optical zone. That is, some surgeons will reduce the diameter of the treated area to treat a greater degree of myopia. This will typically result in excessive night glare. It is important to understand the limitations of these procedures based upon your own prescription and eye characteristics.

Some patients find their best vision after LASIK not as good as with their glasses or contacts, a few find it better, most the same.

The final result depends upon not only the procedure but how the patient heals. Healing determines the speed of visual recovery, the sharpness of vision and the need for enhancement. As the degree of myopia correction increases, the importance of healing to the final visual outcome also increases.

The following are some of the benefits of LASIK:

brief recovery time: Patients are happier quicker
low enhancement rate
very low infection risk
relatively quick procedure to complete
very low risk of scarring
minimal discomfort
high degree of predictability
preservation of the cornea (all corneal layers preserved)
excellent ocular integrity post-treatment
widest range of correctable prescriptions