Flapless Epi-LASIK has many advantages but flap trimming is another good option when surgeons wish to retain the epithelial sheet
Surface ablation is very appealing to me. I have never liked the idea of weakening the cornea to create a LASIK flap, and despite the success of LASIK, I am concerned about ectasia risks and postoperative dry eye.
For these reasons, I have been studying the effects of various surface ablation procedures for several years. We know that LASEK reduced the incidence of sub-epithelial haze compared to PRK, because postoperative coverage of stromal wound surface with epithelium probably limits wound reaction after LASEK.1 However, ethanol toxicity was still a major concern with this procedure, as was the slow visual recovery.
Epi-LASIK, as first described by Dr Ioannis Pallikaris of Greece,2 appeared to solve this problem by allowing the surgeon to mechanically separate the epithelial sheet, without alcohol. Of course, we all thought that a viable epithelial sheet would be one of the major advantages of Epi-LASIK. In theory, that epithelial flap would protect the ablated stromal bed, speed up re-epithelialization, suppress the wound reaction and provide a barrier to cytokine migration.
However, recent scientific data demonstrated that in many cases the epithelial sheet is not really viable. Tanioka in Japan found that most basal cells in epithelial flaps prepared with various epikeratome devices were dead.3 Damage to the basal epithelial cells seems to occur when the basal membrane is lost, which happens more often in Epi-LASIK than previously thought.
With this realization, I and many other Epi-LASIK practitioners began to discard the epithelial sheet rather than repositioning it. This technique appears to produce faster, more stable visual recovery than when the flap is retained.
Epi-LASIK in my practice
We use the Moria Epi-K. This device has a high oscillation speed and low translation speed and makes a very clean epithelial cut margin with little chance of stromal incursion. The long, wide applanation plate of the Epi-K promotes better separation and added safety compared to other epikeratomes. The separator is made from blunt steel and the entire head is disposable. It is operated by the same Evolution 3 console that operates the One Use-Plus and M2 microkeratomes.
In nearly 250 eyes treated with the Epi-K, I have had no stromal cuts. I had one flap tear and small epithelial island in nasal side in three cases. These simply required mechanical debridement on the nasal side.
My current technique is to remove the flap. During surgery, I use chilled BSS, cool, preservative-free eyedrops and apply an ice pack after surgery. The eye is bandaged with an Acuvue Oasys contact lens (Johnson & Johnson Vision Care). I give prednisolone 30 mg for three days, Cerebrex 2000 mg b.i.d., Neurontin 100 mg (gabapentin, Pfizer) q.i.d. and Voltaren (diclofenac sodium 0.1%) q.i.d. for five days.