http://www.crstoday.com/

October 2005

Known Risk Factors for Ectasia

What do we know so far?
By William B. Trattler, MD

Summary of article:

The number of post-LASIK ectasia cases continues to increase since this condition was first reported in 1998.

Two broad groups of eyes appear to be at an increased risk for developing the complication. The first group contains normal eyes that were left with thin residual stromal beds after LASIK surgery. The second group includes eyes with decreased tensile strength (keratoconus, pellucid marginal degeneration, forme fruste keratoconus), whereby the creation of the lamellar flap appears to weaken the cornea and increase the risk for developing ectasia.

As we have learned more about ectasia, there are many gray areas when it comes to its causes. Even with careful preoperative testing and care to leave a sufficient residual stromal bed, a number of patients will still develop ectasia.

Factors include:

Collagen strength

LASIK FLAP strength or lack thereof

Not leaving a sufficient stromal bed

Microkeratomes do not always cut a flap at the specified thickness

There is no good test to measure a patient’s corneal tensile strength.

Enhancements

Dr. Trattler stresses in the article the importance for surgeons to understand that although many patients with keratoconus or pellucid marginal degeneration will present with topographic changes in their teens, other patients may not show signs of keratoconus on topography until their late 20s or 30s. This latter group of patients with normal topography, normal corneal thickness, etc., is still at risk for ectasia.