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Combating corneal ectasia demands that surgeons expand their notions about the disease
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HONG KONG — Surgeons have more advanced and targeted tools at their disposal to precisely screen patients for corneal ectasia, a speaker said here. Bradley J. Randleman, MD, discussed known and presumed risk factors of the disease, as well as screening strategies, in a presentation at the World Ophthalmology Congress.
Dr. Randleman and colleagues at Emory University in Atlanta created a risk assessment model for ectasia, which assigns a point value to a variety of parameters including age, sex, manifest refraction spherical equivalent, preoperative corneal thickness, predicted residual stromal bed and topographic patterns.
They sought to better identify patients who are at high risk of ectasia but might not have presumed risk factors.
"Our goal is to identify 100% of [high-risk] patients. I don't [know] that we will ever achieve that, but it is certainly our goal," he said.
The estimated incidence of corneal ectasia is about one in 2,500, but Dr. Randleman said this number might not be accurate.
"This could be an overestimate because of current exclusion criteria, and we certainly hope this is case. It also could be an underestimate because of the limited follow-up and underreporting because we know ectasia can be a later onset complication," Dr. Randleman said.
The primary risk factors for postoperative ectasia include topographic abnormalities and low residual stromal bed thickness, although Dr. Randleman warned that the conventional wisdom declaring 250 µm as a cutoff value should be eliminated.
"We should wash this number out of our heads as being a cutoff value because we know that a number of cases developed ectasia with a residual stromal bed greater than that, and many normal patients have been lower than that," he said. "It does not have a significant value as a safety cutoff or a risk factor in itself."
Other warning signs include patient age — because corneal tensile strength increases with age — and extreme myopia.
Overall, a comprehensive weighted scale is preferable to looking at individual cutoff values. However, surgeons should be aware that postoperative ectasia can still develop in patients without risk factors or other known intraoperative incidents. This could be due to unidentified ectatic disorders at the time of surgery, patient-related factors such as eye rubbing or other factors that have yet to be determined, Dr. Randleman said.
He encouraged surgeons to carefully screen all patients, eliminate microkeratomes that produce unpredictable flaps and discourage eye rubbing in patients postoperatively. He also urged them to search for additional risk factors and to utilize resources such as Ectasiaregistry.com to enhance the body of knowledge about the disease.