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LASEK effective for correction of myopia
A small study yielded favorable results compared with LASIK. The procedure has advantages over PRK.
Photorefractive keratectomy is a safe and effective method for treatment of low myopia. But because of stromal haze at high myopia after PRK, fast optical recovery and less postoperative pain, LASIK has overtaken PRK almost completely. The intraoperative and postoperative complications unique to LASIK (poorly created or detached flaps, late flap dislocations, epithelial growth within the flap interface and diffuse lamellar keratitis) have led to development of an alternative method.
After the experience of posterior ectasia, corneas under a certain thickness must not be treated with LASIK. The technique of laser epithelial keratomileusis (LASEK) may combine the advantages and eliminate the disadvantages of both PRK and LASIK.
The study
We treated 20 myopic eyes from –2 D to –9 D (average –5.5 D) from July 1999 to November 2000. The study included 14 patients (10 women and 4 men), aged 19 to 53 years (mean age 36 years). Inclusion criteria for surgery were stable refraction and age 19 years or older.
Preoperative examination included manifest and cycloplegic refraction, slit-lamp examination, dilated fundus examination and corneal topography. All patients completed a minimum follow-up of 6 months.
The LASEK procedure was performed using the method originally described by Massimo Camellin, MD.
The pre-incision of the corneal epithelium was performed with a special microtrephine with a 70-µm depth calibrated blade. The trephine is designed to leave a hinge at the 12-o’clock position. Two or three drops of 20% alcohol solution were instilled inside the marker and left for 30 seconds. The area was then dried and thoroughly washed with water and dried again.
Following the same experience as Thomas V. Claringbold II, MD, we applied the alcohol solution between 30 and 40 seconds in the following patient groups: young men, postmenopausal women and long-time contact lens users. We did not use any time of application longer than 40 seconds, to avoid decreasing of elasticity of the epithelial flap.
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The precut margin was lifted and the epithelial flap was gently detached, gathered and folded up at the 12-o’clock position. Thus, an extreme smooth surface was created for the keratomileusis, without epithelial islands and without dents from the hockey-blade spatula.
For the laser ablation we used the Allegretto from WaveLight (Erlangen, Germany). For the eyes in this study, the manifest phoropter refraction was used. (All eyes had cycloplegic refractions within ± 0.5 D of the manifest refraction.) The vertex distance to corneal surface was measured and the patient’s refraction at the corneal plane was determined. In patients older than 40 years, we subtracted 0.5 D.
Cylindrical correction was reduced by 0.25 D to 0.5 D. Then the epithelial flap was repositioned carefully with a small spatula. The epithelial flap is very elastic. A soft contact lens was applied for 3 to 4 days to keep the flap in place. Postoperatively, antibiotic and cortisone treatment was administered for a few days. On the third or fourth day after removal of the contact lens, the epithelial layer was intact.
Stability
Preoperative myopia was –5.5 D on average. This value was reduced to +0.16 D after 3 months. At 6 months postop the average value was –0.19 D.
Predictability
All treated eyes were within ± 1.0 D, 20% were within ± 0.5 D and 60% were within ± 0.25 D.
Safety
Six months postop, 70% of the eyes showed no change in best corrected visual acuity. Fifteen percent were able to improve by one line and 10% by two lines; 5% of our eyes lost one Snellen line.
Efficacy
All treated eyes had uncorrected visual acuity of 20/40 or better, broken down as follows: 20/40 or better, 5%; 20/32, 15%; 20/25, 30%; 20/20, 45%; and 20/16, 5%.
On the first postop day, 50% had UCVA 20/40 or better: 20/80, 10%; 20/63, 15%; 20/50, 25%; 20/40, 25%; and 20/32, 25%. One week postop 90% of the patients had 20/40 or better.
Subjective questioning
One patient complained of strong pain. He lost the contact lens during the second postop night. A central erosion had developed. Another patient complained of mild pain, although the epithelium was intact. Thirty percent of the patients reported light discomfort, pressure and light stinging in the first postop days.
Conclusion
Compared to PRK, LASEK has the following advantages:
- absence of strong postop pain;
- faster optical recovery;
- reduced risk of infection;
- epithelial flap acts as an effective protective barrier.
Compared to LASIK, it has these advantages:
- LASIK requires increased use of complicated mechanical equipment, with a greater potential for surgical complications;
- in the event of infections, they will be subepithelial and not intrastromal, and therefore more manageable;
- risks of infections (diffuse lamellar keratitis) or injury caused by light trauma are reduced. Especially for patients whose professional or recreational activities increase the risk of trauma, LASEK is the superior method.
The disadvantages of LASEK compared with LASIK are:
- postop pain is in some cases greater;
- optical recovery is not quite as fast.
The small number of our patients makes to it difficult to draw conclusions on haze, but epithelial protection should considerably reduce the risk of necrosis of underlying cells, which is the main cause of the problem. In no case was I able to observe haze.
We can conclude that LASEK in this study is an effective method for correction of myopia up to –9 D. For a final assessment of the method, it is necessary to make observations over a longer period of time.
For Your Information:
- Dr. med. Magda Rau, can be reached at Augenärztin Belegärztin, Aepflet 24, 93437 Furth im Wald, Germany; +(49) 9973-802593; fax: +(49) 9973-500753; email: info@privatklinik-dr-rau.de.