Lasek is an anagram for Laser Assisted Sub-epithelial Keratomileusis. This operation is performed by folding back the corneal epithelium and then applying Excimer laser treatment to the underlying corneal tissue to alter its shape in a pre-determined manner. The corneal epithelial cell layer can first be loosened with an alcohol solution which is placed in a well on the surface of the cornea for a short period of time (i.e. about 15 seconds).

Alternately the epithelium flap can be fashioned with an epithelial debrider without the necessity to use alcohol to first loosen this cell layer. This is then known as Epi-lasek.

After the procedure a bandage contact lens is placed on the surface of the eye for the first few days. This allows the surface epithelial cells to heal back into position more quickly. It also makes this recovery period more comfortable for patients. The recovery period is more prolonged than it is with Lasik. The surface cells first have to heal and provide a good regular optical surface prior to the best visual result emerging. However, it has been well documented that the long term visual outcome is equally as good with both these techniques. It is more uncomfortable after the operation than it is with Lasik and eye drops may be required for a longer period after surgery.

Lasek is used as an alternative procedure to Lasik in certain circumstances (e.g. where there may not be sufficient corneal tissue to allow the fashioning of a corneal flap and to treat the refractive error underneath the flap). It may also be used where there is a very steep/flat cornea or a very large night-time pupil.