Early diagnosis is the first step in effective keratoconus treatment

June 28, 2013

 

San Diego-Barry Eiden, OD, and Clark Chang, OD, presented the Pat Cummings Memorial Course at the American Optometric Association annual meeting on Friday morning. The course-titled Contemporary Concepts in the Diagnosis and Treatment of Keratoconus and Keratoectasia-was a call to action to eyecare professionals to pay attention to the earlier signs and symptoms of this very serious condition.

“If you’re seeing Vogt’s striae as the initial presentation, it’s too late,” warned Dr. Chang. Hydrops is another sure sign that you’re too late, he added.

Keratoconus is the number one reason for penetrating keratoplasty. What’s more, as Dr. Eiden pointed out, some 7000 penetrating keratoplasties occurred in the Unites States alone last year, secondary to keratoconus. The presenters agreed that’s far too many cases, and called for optometrists to understand how to interpret the many warning signs so that earlier intervention can be possible.

“The diagnosis of keratoconus is like dry eye disease,” said Dr. Chang. “The earlier you can diagnose, the better the outcome will be.”

One of the most obvious warning signs is family history, the presenters said. Among the 1065 participants of the collaborative longitudinal evaluation of keratoconus (CLEK) study, 13.5% reported a family history at baseline. The CLEK study was strictly observational; in this same group 9.3% had penetrating keratoplasty in one eye during the 8-year study period.

Drs. Eiden and Chang identified several optical symptoms of keratoconus, including diplopia and polyopia (monocular especially). A non-traumatic rapid increase in myopia should also be a red flag. When performing retinoscopy, optometrists should pay special attention to the scissors reflex and Charleaux oil droplet signs. Another key sign: the telltale crab-claw pattern.

The presenters emphasized that topography is not the be-all-end-all and cited these limitations to placido topography:

  • There is no analysis of posterior surface.

  • There is no representation of thickness.

  • It does not measure central cornea.

  • It has problems with irregular surfaces and unstable tear films.

  • You get limited corneal area measures.

  • Curvature has its own limitations.

Some newer technologies that can be used to help diagnose keratoconus include epithelial remodeling (wavefront analyzer), the Artemis high frequency B-scan, the Optiwave Refractive Analysis (ORA), and Corneal Biomechanics (Corvis ST).

Dr. Eiden also discussed the differences in topography versus tomography. Tomography is a direct measure of corneal elevation,” he said. “Our Pentagram scanner is like a topographer on steroids.”

Global pachymetry is also very important. Pachymetry indicates the thinnest spot and shows pachymetric progression. The percentage thickness increase is very telling and is more sensitive than thickness measures alone. Note that the thinnest part of the cornea is generally not central.

When diagnosing and managing keratoconus, the story is often on the back side, said Dr. Eiden. “The anterior surface is only half the exam. If you’re only looking at the anterior surface, it can really hurt you.” He added that sometimes, a clinician may think a case is unilateral when it’s not.

“We have the possibility to intervene early,” Dr. Eiden said. “Not to do so is a crime.”ODT