Role of Corneal Epithelial Measurements in Differentiating Eyes with Stable Keratoconus from Eyes that Are Progressing

PURPOSE: To evaluate measures of corneal epithelium in eyes that showed documented signs of keratoconus (KC) progression and compare with stable eyes and healthy controls. Also, to determine the correlation of these epithelial parameters with maximum keratometry (K max) and pachymetry. DESIGN: Prospective, observational, comparative study. PARTICIPANTS: One-hundred and fifty eyes from 150 patients. The study included 50 eyes from patients with documented KC progression, 50 eyes with stable KC, and 50 clinically normal eyes to serve as controls. METHODS: A spectral–domain (SD)-OCT imaging was obtained in all eyes, and mean values were compared between the groups. The correlation of epithelial parameters with K max and thinnest pachymetry was also investigated. MAIN OUTCOME MEASURES: For the purposes of this study, the epithelial measures maximum, minimum, superior, and inferior values as well as the difference between the minimum and maximum (min–max) and epithelial standard deviation were considered, obtained from SD-OCT and compared between groups. Measurements of the thinnest point and min–max in pachymetry were also recorded. RESULTS: The only epithelial parameter that presented a statistically significant difference between stable and progressive KC was epithelium min–max. Although stable KC presented epithelium min–max mean values of −18.2 ± 6.6, progressive KC eyes presented mean values of −23.4 ± 10.3 (P < 0.0001). Epithelial maximum (P = 0.16), minimum (P = 0.25), superior (P = 0.28), inferior (P = 0.23), and standard deviation (P = 0.25) values were not significantly different between stable and progressive eyes. Difference min–max pachymetry points in stable (−108.3 ± 33.5) and progressive KC (−115.2 ± 56.0) were not significantly different (P = 0.723). There was no significant correlation between epithelium min–max with corneal thinning (P = 0.39) or K max (P = 0.09) regardless of disease progression. CONCLUSIONS: Epithelial measures are useful to identify KC eyes that are progressing; the parameters that measure the difference between min–max epithelium points were significantly different between stable and progressive groups, unlike this difference in pachymetry. Finally, this epithelial parameter seems to be independent of corneal thinning and K max. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.