The eye has an internal pressure that helps it maintain its shape. The cornea accounts for 80% of the refractive power of the eye. Refractive surgery attempts to reshape the cornea by removing some of its tissue. When the internal pressure of the eye overcomes the strength of the thinned cornea, the result is ectasia. Typically, ectasia manifests in the inferior, or lower, portion of the cornea, and is easily observed from the side, as shown in these pictures.
Ectasia may develop months or years following what appears to be a successful LASIK. The industry maintains that ectasia is rare, but the true rate is probably much higher.
Advanced ectasia is often treated with cornea transplant. This is the wrong approach, but surgeons like to cut. There's an old saying: When all you have is a hammer, everything looks like a nail. Transplants typically have a lifetime of approximately 15 years, and must be repeated several times during the life of the patient. Healing takes up to a year, and there is no guarantee that visual quality will be acceptable, meaning that the patient may have a transplant and require specialty lenses anyway.
Because a scleral lens functions as an artificial cornea, it is possible to restore vision while avoiding a transplant.
Click on any image below to view that image in high resolution. This a small sample of patients from my practice.[widgetkit id=1]
Ectasia can also be seen on topography. Our equipment generates a 3-dimensional topography of the post-LASIK eye. The patient below was a -18 before LASIK, meaning that an extraordinary amount of tissue was removed in an attempt to flatten the cornea correct the patient's vision. Unfortunately, this excessive thinning resulted in ectasia, a progressive bulging of the cornea under the influence of intraocular pressure.
This patient's other eye had -15.00 of myopia. The 3-D topography of that eye looks pretty much the same. This patient underwent LASIK in 2000. He developed this highly distorted cornea shortly after undergoing LASIK. Sadly, this patient also developed open angle glaucoma in both eyes. It is difficult to say if the LASIK hastened the glaucoma. He is currently wearing scleral lenses which is providing him with 20/40 vision in each eye.
Another 3-dimensional topography of an eye with ectasia.