Refractive Surgery

Until November of 1995, the only form of refractive surgery available in the US was radial keratotomy, (RK). Although radial keratotomy has been around for over 20 years, the great majority of all ophthalmologists, including all the doctors of Affiliated Eye Surgeons, did not perform this surgery for the following reasons:

• The risk of a significant, permanent decrease in best corrected visual acuity, (BCVA), was too high.

• The results were extremely variable.

• The final correction was extremely unstable. Approximately 30 percent of all patients have had a progressive flattening of the cornea leading to a progressive farsightedness. We have a patient in our practice that had RK done by another doctor. He was originally 6 units, (diopters), nearsighted. Originally, postoperatively he was 20/20 without glasses, but unfortunately, his cornea continued to flatten and now he is 3 units, (diopters), farsighted, and is getting more farsighted every year.

In November of 1995, the FDA approved the Excimer laser for correction of nearsightedness. In April of 1998 they also granted the Excimer laser the ability to correct nearsightedness with accompanying astigmatism. In January 2001, the FDA approved the Excimer laser for correction of Hyperopia, (farsightedness), with astigmatism. There are now two ways to correct nearsightedness, nearsightedness with astigmatism, and farsightedness with astigmatism with the Excimer laser. Both methods are now approved by the FDA. The first way is by laser surface ablation, (PRK or LASEK). For the remainder of the text, laser surface ablation will be referred to as PRK. The second way is by Laser Assisted Stromal In-Situ Keratomileusis, (LASIK). Until recently, there was real controversy in the field of ophthalmology about which of these procedures is preferable.

Even as recent as December of 1998, the general consensus was that the lower degrees of myopia, (less than 4 diopters of myopia), should be done using the PRK technique. However, a new microkeratome has been invented called the Hansatome. This microkeratome is much safer than the microkeratomes that have been used in the past. A recent survey of all LASIK refractive surgeons show that 60% of them use the Hansatome microkeratome. The other 40% collectively use the other four microkeratomes that are currently being used. This statistic alone shows the superiority of the Hansatome microkeratome. Recent papers have shown the visual results of the PRK and LASIK procedures are identical. There is a 1% chance in both groups that the patient could have a complication which would permanently reduce vision. The complications in the PRK group are either infection or late haze. The complications in the LASIK group are infection, flap complications, and epithelial ingrowth.

The following are our observations:

Advantages of PRK

• PRK is technically easier to do. The only surgical step is that the ophthalmologist must remove 6 mm of corneal epithelium, which is a simple step.
• PRK was the original operation and has a 10 year history of being a safe, predictable operation.
• PRK is the operation of choice in people that have thin corneas and several other corneal conditions which would prevent LASIK. We suggest to approximately 1 out of 10 of our patients that PRK would be the operation of choice for them. Of the remaining patients, we normally encourage them to have LASIK. It is important to remember that the visual result from both of these procedures are identical.
  

Disadvantages of PRK

• The epithelium does have to be removed. It does regenerated in approximately 3 days. During this time, the patient wears a clear bandage contact lens for comfort. However, there is more discomfort with PRK than there is with LASIK
• Haze can develop many months after the surgery. This can be treated, but it is a nuisance to have this develop.
• The return to excellent visual acuity following PRK is slower than it is with LASIK. For this reason, only one eye is done at a time.
• The most important disadvantage to PRK is that it is very difficult to retreat the eye in case there is an under-correction. If there is an under-correction, then the whole procedure including the removal of the epithelial cells and the wearing of the contact lens has to be repeated. This is the main reason why we are now advocating LASIK surgery as the procedure of choice.
  

Advantages of LASIK

• There is less discomfort for the first three days following the procedure.
• Haze is not a significant problem.
• Both eyes can be done at the same time.
• Visual recovery is significantly quicker than with PRK.
• The most important advantage is that it is very easy to do an enhancement. It is easy to lift the flap for the first six to twelve months following the initial procedure to obtain additional flattening of the cornea in cases that are under-corrected.

Disadvantages of LASIK

• With the new Hansatome microkeratome, flap complications still occur in approximately 1% of patients. Most of these flap complications can be handled by another surgery.
• Epithelial ingrowth beneath the flap can occur after the surgery. This can be handled by lifting the flap and removing the epithelial cells.

In a recent issue of Refractive Market Perspectives, a survey was made of all the refractive surgeons in the United States. It was interesting to see that 63% of all LASIK surgeries were done by the VisX Star IV laser. The VisX Star IV is equipped with wavefront technology which is the most recent improvement for laser vision correction. The VisX Star IV wavefront technology called Custom Vue further enhances the excellent survival results of LASIK. It is also interesting to note that 52% of the LASIK cases used the Bausch & Lomb Hansatome microkeratome. Both of these instruments are used where Dr. Bloemker performs surgery at the Scottsdale Eye Laser Center..