I read the study by Asroui and associates with great interest. The authors evaluated the influence of corneal epithelial thickness mapping on refractive surgery candidacy screening among 100 patients in a single refractive surgical practice. They concluded that the use of epithelial maps changed surgical candidacy in 16% of the study population and altered surgical decision-making in 25%.
Besides the subjective nature of the study and not assessing the impact of the decision changes on actual clinical outcomes, I would like to comment on several additional issues in the article.
The authors failed to provide essential information on the statistical analysis used in the study. The test-retest reliability coefficients and Cohen’s kappa values should have been provided to allow an objective assessment of intra- and inter-observer reliability regarding refractive surgery candidacy.
In this study, a Scheimpflug-based tomographer (Pentacam HR version 6.09r43, Oculus Optikgeräte GmbH) and an anterior segment optical coherence tomographer (AS-OCT) (Avanti RTVue XR version 2018.1.1.63, Optovue) were used for corneal tomography and epithelial thickness mapping, respectively. The authors stated in the methodology that: “soft contact lens wear was discontinued at least 3 days prior to initial screening”. It is well-known that contact lens wear significantly affects both corneal topography and epithelial thickness due to corneal warpage or edema, and thus soft contact lenses should be removed for at least 1 week (actually many researchers advocate 2 weeks) prior to refractive surgery screening. However, the authors ignored this widely accepted rule, which may have significantly altered the results of the current study.
I am also concerned about the explanation for the case presented in Figure 2, which states: Corneal imaging from the right eye of a patient who was initially deemed to not be a candidate for corneal refractive surgery based on clinical evaluation ……….. but was ultimately deemed to be a surgery candidate based on the epithelial thickness map finding of inferior thickening co-located with the region of suspicious steepening on anterior curvature .
The authors should have followed a logical flow to locate the possible “cone” that starts from the thinnest point on the corneal thickness map and proceeds across co-located points (with the thinnest point) on the back elevation, front elevation, and epithelial thickness maps (red arrows in Figure 1 ) rather than looking at the steepening area on the axial curvature map, which does not always coincide with the cone. The Belin/Ambrósio Enhanced Ectasia Display, as one of the most valuable screening tools for detecting subclinical and forme fruste keratoconus, also places a strong emphasis on the front and back elevation values at the thinnest corneal point and the distributional profile of corneal thickness emerging from the thinnest point. Therefore, the authors should have looked for epithelial thinning or thickening at the thinnest corneal point, presumably overlying the “cone” (small red circle in Figure 1 ) as they correctly did when assessing the other case in Figure 3 in the original article. Figure 3 clearly demonstrates the focal epithelial thinning area that perfectly coincides with the thinnest corneal point and suspected elevation islands on topography, validating my aforementioned statement.