Ectasia is a condition that occurs when the cornea is so thin that intraocular pressure (IOP) leads to instability and bulging of the cornea. This causes blurring, myopia, and irregular astigmatism.
During laser-assisted in situ keratomileusis (LASIK), the surgeon creates a flap in the outer layer of your cornea and uses the laser to remove some of the lower corneal tissue that is exposed when the flap is moved aside. If your corneas are thinner than normal, you may be at an increased risk for ectasia following LASIK, especially if you require additional LASIK procedures to fine-tune your vision correction. It is even possible (though extremely rare) for ectasia to develop following photorefractive keratectomy (PRK), a surface laser procedure that does not involve creating a corneal flap.
If you have thin corneas, you may not be a good candidate for LASIK. Ask your eye doctor if alternative refractive procedures such as epi-LASIK or PRK might offer you a better chance at improved vision without any unnecessary risk of adverse side effects.