What is a thin flap? (Posted: jan 2005)

A thin flap is a LASIK flap which is in fact cut thinner than the microkeratome was programmed for.

What causes it? (posted: jan 2005)

Microkeratome accuracy tolerances are not very good, as has been well documented in the medical literature. Differences of 20% or even more from the programmed thickness are not at all unusual. Additionally, anatomical features will affect the thickness of a flap. Studies have shown that thinner corneas will typically have thinner flaps. Eye size, corneal steepness or flatness also may play a role.

What does it mean for the patient? (posted: jan 2005)

A thin flap in and of itself is not a problem, unless it is so thin that it cannot be handled safely without, for example, a buttonhole; or it is both thin and irregular - or thinner in one part than another; or it is thinner than the basic threshold for a good visual outcome.

How is it measured? (posted: jan 2005)

Flap thickness cannot be measured accurately with any equipment that is in common use in ophthalmologists' or optometrists' offices. It can be measured with confocal microscopy or Artemis VHF digital ultrasound. The latter analyses the features of the epithelium, flap and stroma in great detail.