Corneal K-Values as a Diagnostic Screening Tool for Marfan Syndrome

Marfan syndrome (MFS) is diagnosed based on Ghent nosology, including major and minor criteria such as increased axial length (AXL) and flattened corneal curvature (higher K-values) or myopia of more than -3 diopters (D) in its latest revision. Because corneal flattening may, in part, be caused by AXL increase, it may be helpful to consider K-values separately. We present statistical evaluation of using corneal K-values for identifying MFS.

A retrospective study of K-values of 74 right eyes of 74 patients with MFS, who were compared with an age- and AXL-matched group of 74 right eyes of 74 patients without MFS. After multivariate analysis, receiver operating characteristic curves were calculated.

Mean age was 44.1 years versus 44.9 years (P = 0.834). Mean AXL was 25.22 mm versus 25.47 mm (P = 0.661). K-values showed significant differences: mean Kmax was 8.25 mm (40.91 D) versus 7.9 mm (42.72 D) (P < 0.001) and mean Kmin was 8.22 mm (41.06 D) versus 7.69 mm (43.89 D) (P < 0.001). The area under the curve in receiver operating characteristic analysis was 0.82 for Kmax and 0.78 for Kmin; the best cutoff was seen at a Kmax of at least 8.16 mm (41.36 D; sensitivity 73% and specificity 81%).

Although both K-values differ significantly, Kmax is the better marker to identify MFS. A Kmax of more than 8.16 mm (41.36 D) seems to be a reasonable cutoff (specificity of 81% and sensitivity of 73%). Because this biometric value is easily obtained and standardized, we see it as a good supporting screening tool for MFS suspects.