Free and Irregular Flaps
Free flaps and irregular flaps are complications that can occur during LASIK surgery when a microkeratome is used to create the corneal flap prior to the laser ablation.
If the microkeratome cuts across the entire cornea without making a hinge, a "free flap" or "free cap" results. In the hands of a skilled surgeon, a free flap can be repositioned on the eye to avoid a serious vision problem. With advances in microkeratome technology, free caps occur less frequently today than in the early history of LASIK. With modern microkeratomes, it’s estimated that free caps and all other flap complications combined occur in less than 0.3% of LASIK procedures.
Other possible flap complications include incomplete flaps, and buttonhole flaps (an unwanted hole is created in the center of the flap. Most flap complications occur because of a malfunction of the microkeratome, a loss of suction on the suction ring that attaches the microkeratome to the eye during flap creation, or an unusual corneal response to the compression that occurs when the microkeratome is attached to the eye.
If a flap complication occurs during LASIK, the surgeon will usually stop the procedure, replace the flap, and let the cornea heal before attempting the surgery again. It may take several months before the cornea is ready for a second attempt. Some surgeons will recommend PRK rather than LASIK on an eye that has had a flap complication to prevent a second occurrence of the problem.
The risk of free flaps and other flap complications is essentially eliminated when flaps are created with a femtosecond laser rather than a bladed microkeratome.