A thin, irregular, or buttonhole flap is a significant complication of lamellar surgery that typically calls for aborting the case. Thin, irregular or buttonhole flaps can occur with all keratomes, including the new femtosecond devices. The cause of a thin, irregular, or buttonhole flap is often unclear and can be multifactorial. Causes of a thin, irregular, or buttonhole flap may include low pressure, poor corneal lubrication, poor blade quality, preexisting corneal pathology, or a keratome malfunction. Most thin, irregular, or buttonhole flap cases can be redone with either LASIK or PRK and do have a good prognosis. Remember, the key when faced with a poor flap typically is not to ablate.