New Model for Predicting Ectasia Risk

During Friday’s Refractive Surgery Subspecialty Day, Steven C. Schallhorn, MD, chief medical officer at Zeiss and chief medical director of Optical Express, presented predictive modeling data that bring into focus the true risk of developing post-LASIK ectasia.

He developed a logistic regression model using a database of 199 LASIK eyes of 146 patients who developed ectasia and a control group of 361,848 eyes of 184,728 consecutive LASIK patients treated at the same time (5-9 years ago), as well as topography of 3,700 eyes of 1,850 patients who underwent LASIK 7 years ago. Univariate analysis produced many hits, but multivariate logistic regression indicated that the most significant risk factors for ectasia after LASIK were abnormal corneal shape and age:

Abnormal corneal shape

• Odds ratio (OR) for forme fruste keratoconus (FFKC) is 21:1; predicted incidence is 1:161.
• OR for inferior steepening or skewed radial axis is 5:1; predicted incidence is 1:484.

Age:

• OR for age less than 30 years old is 2.5:1; predicted incidence is 1:830.
• Chance of developing ectasia in a young patient with FFKC is 1:151 (1:80-1:550).

“We can now really talk about the chance of developing ectasia after refractive surgery, not just increased risk,” Dr. Schallhorn said. “A patient with forme fruste keratoconus is 20 times more likely to develop ectasia, but the incidence is 1 in 161. It’s still less than 1%.” —Susanne Medeiros

Financial disclosure. Dr. Schallhorn: Abbott: C; Zeiss: C.

Disclosure key. C = Consultant/Advisor; E = Employee; L = Speakers bureau; O = Equity owner; P = Patents/Royalty; S = Grant support.