Corneal Ectasia – A Clearer Understanding of Vision Distortion
Corneal ectasia occurs when the inner layers of your cornea become weak, causing the cornea to change shape, protrude forward and distort your vision. In rare cases, it can be a complication of LASIK.
If you are one of the few people to experience post-LASIK ectasia, the good news is that new methods are available that may allow your surgeon to treat it. However, it is important to understand that corneal ectasia is a serious condition that can cause permanent loss of vision if not treated, and may require a corneal transplant. It cannot be corrected with glasses.
Though ectasia is uncommon — and advances in technology and treatment have made it even less common in recent years — experts are unsure as to what percentage of patients are at risk of developing the condition as a result of LASIK.
LASIK patients are more likely to develop corneal ectasia than are patients undergoing other refractive surgeries.
Post-LASIK Ectasia Causes
Experts believe that post-LASIK ectasia is caused by removing too much corneal tissue during LASIK surgery. When this happens, the remaining corneal tissue, or “residual corneal bed,” ends up being too thin, in turn weakening the cornea and allowing it to bulge under normal eye pressure. The bulging can distort your vision.
The following are potential risk factors for post-LASIK ectasia:
Severe Myopia. If you have severe myopia (nearsightedness) you are at greater risk of developing ectasia following LASIK because more tissue will need to be removed from the center of your corneas to correct your refractive error.
Thin Corneas. The thickness of the central portion of the cornea prior to surgery is an important factor. If you have thin corneas you are at higher risk of developing ectasia following LASIK.
Unusual Corneal Shape. This is a possible risk factor even if the thickness of the cornea is normal. For this and other reasons, refractive surgeons measure the curvature of the corneas in a test called corneal topography (prior to performing LASIK).
Young Age. There is some evidence to suggest that younger patients are at higher risk for ectasia.
Disparity in Corneal Thickness. If the thickness of the central portion of your right eye’s cornea is different from the thickness in the left eye, you are at higher risk of developing ectasia.
To test for risk factors, LASIK surgeons measure the thickness of your central cornea to determine how much tissue needs to be removed to correct vision. This allows them to estimate how much residual corneal bed will be left following the procedure.
The main symptoms of post-LASIK ectasia are blurry and distorted vision. The onset of these symptoms may take place anywhere from a month to a year and a half following surgery, and sometimes even longer.
The post-operative exams conducted by your surgeon will help him or her determine if you are experiencing complications such as ectasia.
Ectasia can usually be treated. Treatments for ectasia are similar to those used to treat a condition called keratoconus (another distortion of the eye’s shape).
Thanks to advancements in technology, some patients with ectasia can now benefit from a procedure called corneal collagen cross-linking (CXL). Read more in the article about CXL.
Alternatives to LASIK for Patients at Risk
If pre-operative tests show that you are not a good candidate for LASIK due to the risk of ectasia, you may still have options. Refractive procedures that don’t involve a deep corneal flap — such as PRK, LASEK and epi-LASIK — may be a good bet. These procedures remove less corneal tissue, so the residual stromal bed is thicker than it is with LASIK.
Other alternatives to LASIK include lens-based treatments such as phakic IOLs (intraocular lenses) and refractive lens exchange, which do not remove any corneal tissue.
Finally, some refractive surgeons are offering a new procedure that combines PRK with corneal cross-linking. This procedure leaves a thick residual stromal bed and makes the corneal tissue stronger at the same time.