Gauging Fuchs Prognosis With Scheimpflug Tomography

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Researchers at Mayo Clinic have harnessed a common imaging technology in a way that may be a game-changer in assessing Fuchs endotheli­al corneal dystrophy (FECD).¹ Using Scheimpflug imaging, they found that the presence of three parameters—loss of regular isopachs, displacement of the thinnest point of the cornea, and focal posterior surface depression—could be used to predict risk of disease progres­sion or need for surgical intervention.

And although central corneal thickness (CCT) is often used to gauge whether keratoplasty is needed, CCT proved to be a weak predictor of prog­nosis, especially in the absence of pre­vious CCT measurements and clinically definite edema. Another prognostic factor—anterior corneal backscatter—also proved to be weakly predictive.

“Clinicians should recognize that Scheimpflug tomography can deter­mine if corneas with FECD might be contributing to visual symptoms, es­pecially in the absence of an advanced cataract, other comorbidity, or clinically obvious edema at the slit lamp,” said Sanjay V. Patel, MD, FRCOphth, at the Mayo Clinic in Rochester, Minnesota. “The images are easy to acquire and interpret in clinical practice, and they help determine prognosis.”

FUCHS PROGRESSION. (Left column) Pachymetry maps were evaluated for loss of parallel or almost circular isopachs and for displacement of the thinnest point of the cornea (small circle). (Right column) Posterior elevation maps were evaluated for focal posterior surface depression. All images taken in the same eye.

Study specifics. For this study, Dr. Patel and his colleagues used the Pentacam HR (Oculus) to evaluate 56 patients (96 eyes) who had a range of FECD sever­ity. The patients were followed for a median of five years to determine whether imaging find­ings, anterior corneal backscatter, or CCT could predict disease prognosis. Progression was defined as the new onset of clinically definite edema, a 5% or more increase in CCT, or surgical intervention with endothelial keratoplasty (EK).

Evaluating risk. At five years, when none of the three Scheimpflug param­eters were present, the cumulative risk of progression was 7%, reflecting the natural progression of the disease. This increased to 48% when one or two parameters were present and to 89% when all three parameters were present.

Loss of regular isopachs and displacement of the thinnest point of the cornea were independent and clinically important risk factors for progression, conferring an 8-and 4-fold risk of progres­sion, respectively. In contrast, anterior corneal backscatter was a weak predic­tor of FECD progression/intervention, and CCT was a risk factor only in eyes with definite edema at slit-lamp exam.

Risk after cataract surgery. Research­ers also considered the 27 eyes that underwent uncomplicated cataract surgery after enrollment. The four-year cumulative risk of progression/inter­vention was 0% when no tomographic parameters were present, 50% with one or two parameters, and 75% with all three parameters.

Who should be imaged? Patients who have clinically obvious edema at the slit lamp do not need Scheimpflug imaging, Dr. Patel said. Neither do patients who do not appear to have edema and are asymptomatic with normal vision. “For other patients with FECD, or when cataract surgery is being considered, we strongly recom­mend imaging.”

He suggested that clinicians might use the results to counsel patients about whether EK may be appropriate. He added that the study’s findings might prevent unnecessary EK procedures, including those undertaken too early in the course of the disease.

A note on CCT cutoffs. “There are published articles that suggest proceed­ing to keratoplasty above different CCT cutoffs,” Dr. Patel. “I hope that these notions can be abandoned given our findings that CCT was very weakly pre­dictive of prognosis, if at all, whereas the tomographic features were highly predictive.”

—Miriam Karmel

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1 Patel SV et al. Ophthalmology. Published online Sept. 27, 2019.

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Relevant financial disclosures—Dr. Patel: None.

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