About A Better PRK (LASEK)
The following article is from the Healthcare Publication:
Ophthalmology Times, Vol. 26, No. 14, July 15, 2001
By JULIA TALSMA
Reviewed by Daniel S. Durrie, MD, and Michael J. Collins Jr., MD
SAN DIEGO - Refractive surgeons can soon add another technique to their repertoire with laser sub-epithelial keratomileusis (LASEK), which compares favorably with the outcomes seen with LASIK, said Daniel S. Durrie, MD, at the annual meeting of the American Society of Cataract and Refractive Surgery (ASCRS).
LASEK differs from LASIK in that the surgeon creates an epithelial flap instead of a corneal stromal flap, thus eliminating all the complications associated with deeper corneal stromal flaps, explained Dr. Durrie, associate clinical professor, University of Kansas, Kansas City.
"During this meeting (ASCRS), we will spend a lot of time talking about corneal flap complications, epithelial ingrowth, diffuse lamellar keratitis, refloats, and enhancements," said Dr. Durrie, a surgeon at the Hunkeler Eye Centers, Kansas City Region, Overland Park, KS." But we wouldn't have to do this if we didn't make a corneal flap."
Dr. Durrie presented the results of Dan Epstein, MD, and Paolo Vinciguerra, MD, who treated 746 cases with LASEK. Preoperative refractive errors ranged from -15 to 5 D.All patients were treated with the Nidek laser.
The 2-year stability curve showed that 94% of the patients had an outcome of 20/20 or better. These results, which really piqued Dr. Durrie's interest, were first presented at the European Society of Cataract and Refractive Surgery last year, he said.
Dr. Durrie is conducting his own randomized prospective study by comparing LASEK in one eye and LASIK in the other. He presented the results of the first 29 eyes, which were all myopic up to -9 D.
The average visual acuity 1 hour after the procedure is 20/50 in both eyes. One day post-op, the LASEK average visual acuity was 20/30, a little worse than the average for LASIK at 20/20-.However, the average visual acuity for LASEK at 1 month is 20/20, with a range between 20/15 and 20/40.
"We are also comparing the wave-front analysis of these cases," Dr Durrie said.
"Most of us think that we create some aberrations with the LASIK flap that we might be able to eliminate with LASEK," he added.
The LASEK technique is fairly straightforward. The surgeon places an epithelial trephine on the eye, which is centered on the pupil and pushed downward to create an epithelial cut with a superior hinge. Then the surgeon places a well of alcohol solution (ETOH) on the cornea that is slightly wider than the trephine cut for 30 seconds.
The surgeon then removes the alcohol, rinses the eye surface with balanced salt solution (BSS), and uses a Weck cell sponge to dry the edge of the epithelial flap.
"You will have two indentations-one from the trephine and the other from the well that you held on the eye. So you have to figure out which one is which," Dr. Durrie said.
Then starting a break in the area outlined by the trephine and continuing along that cut make an epithelial rhexis. The epithelial flap is gently pulled toward the superior hinge and Bowman's membrane is polished with a Weck cell sponge.
The exposed area is treated with the laser, just like in the LASIK procedure. The epithelium is replaced and a bandage contact lens is used to protect the eye, he said.
"I now use an eight-incision keratotomy marker with rose Bengal to mark the epithelium before making the flap. This helps with proper alignment when I put the epithelium back," Dr. Durrie said.
"I prefer rose Bengal over gentian violet because it is a little less toxic and gives you nice thin marks," he added.
After the laser ablation, the surface is much smoother than with LASIK. He then places BSS on the surface before replacing the epithelial flap. With a spatula-like instrument, he pushes the flap back into place and lines up the rose Bengal marks.
"The epithelium does stretch a little bit, so it is fine to let it overlap," he said.
Dr. Durrie blows the surface dry lightly with oxygen. He then re-wets the surface of the eye with BSS and places a bandage contact lens.
Because the LASEK technique is relatively easy, Dr. Durrie encouraged others to try it after viewing a video.
A Safe Procedure
"LASEK is a safe and viable alternative for LASIK and PRK. It is easy to perform and a good alternative for the conservative doctor and a conservative patient," he noted.
As far as haze is concerned, Dr. Durrie said he has noticed some fine reticular haze in a couple of patients that has not been visually significant. To reduce or eliminate the risk of haze our surgeon uses Mitomycin-C During the procedure.
In other studies, there has not been or any significant grade III or higher haze or any significant regression.
If an enhancement is needed, the same procedure would be used, he noted.
Michael J. Collins Jr., MD, cornea and refractive surgery fellow, Hunkeler Eye Centers, was Dr. Durrie's co-author for this article.
Epithelial trephination centered on pupil. The area between the two superior notches is dull to make a "hinge" when downward pressure is used to cut the epithelium.
Placing the ETOH. A well or cone slightly larger in diameter than the epithelial trephine is used to hold a 20% ETOH solution to soak the epithelium for about 30 seconds. The ETOH is removed with a dry Weck sponge, the surface is rinsed with BSS, and another dry Weck sponged is used to outline the trephined area.
Using the micro-hoe to start the epithelial flap. The hoe is pressed firmly downward and pulled about a millimeter toward the pupil center.
The epithelial flap is started in this fashion along the entire area of trephination up to the hinge.
Note the smooth and glistening area exposed after the epithelium is pulled back as a flap. Bowman's membrane is polished with a dry Weck sponge before the laser ablation is performed.
Replacing the epithelial flap after the laser ablation. BSS is placed on the surface and gently rubbed into the exposed area; a few drops are also put on the superior epithelial flap. The epithelial flap is then gently unfolded and the rose Bengal marks are aligned.
Eye after epithelial flap has been replaced. The epithelium is examined to make sure it is properly aligned.
Using oxygen to "shrink wrap" the epithelial flap onto the surface. The oxygen is used at 2 L/M in small spurts to dry the surface of the epithelium lightly to help secure it into place.
Eye after placement of soft contact lens and removal of speculum. BSS is placed on the eye for lubrication before the bandage contact lens is placed. The speculum is removed and the patient is asked to blink gently to ensure the epithelial flap and contact lens stay in place.
|Almost painless.||Most patients have 2 - 4 days of discomfort and some pain after the procedure. RX for pain are given to reduce your discomfort.|
|Most patients can comfortably drive within 24 hours of having the procedure.||Vision is blurred for 3 - 7 days following the procedure.|
|Vision in most patients is stable after 2 - 6 weeks.||Vision may fluctuate for 1-6 months.|
|Eye drops used for 1 week only.||Eye drops necessary to control the healing process for 1 - 4 months.|
|Very little aftercare necessary because of minimal healing response.||Some additional post-operative visits may be necessary to ensure proper healing.|
|Flaps may cause some aberrations and some minor flap complications.||No flap is needed.|