Epithelial Measures Demonstrate Usefulness for Detecting Keratoconus Progression

Epithelial measurements may identify keratoconus (KC) progression — particularly those that measure differences between minimum and maximum epithelium points, according to a study published in Ophthalmology Science.

Researchers enrolled 150 patients in a prospective, observational study which included individuals with progressive KC (maximum keratometry [Kmax] increase of 1.00 diopters [D] per year; n=50; mean age, 22.7 years) patients with stable KC (n=50; mean age, 23.3 years) and control group participants (n=50; mean age, 23.6 years). All participants underwent spectral domain-optical coherence tomography (SD-OCT) imaging to obtain pachymetry and epithelial thickness maps. Minimum and maximum epithelial thicknesses of the map (epithelial min and epithelial max, respectively), the difference between minimum and maximum epithelial thicknesses of the map (min-max), and superior, inferior, and epithelial standard deviations were compared between groups. 

Epithelial min-max was the only epithelial parameter that was significantly different between individuals with stable and progressive KC. Patients with stable KC presented with mean [SD] epithelial min-max mean values of -18.2 [6.6] compared with -23.4 [10.3] among individuals with progressive KC (P <.0001). 

The epithelial max (P =.16), epithelial min (P =.25), superior (P =.28), inferior (P =.23), and standard deviation (P =.25) values were not significantly different between patients with stable and progressive KC. There was no significant correlation between epithelial min-max with corneal thinning (P =.39) or k max (P =0.09) regardless of whether KC was progressing. 

Epithelial min and inferior presented a significant correlation with corneal thinning (P =.0010 and P =.0014 respectively) and kmax (P =.0041 and P =.0008 respectively) in eyes experiencing KC progression, according to the report. 

“The meaningful difference in the Min-Max variable between stable and progression eyes is even more interesting as there is no significant correlation between this epithelial parameter and corneal thinning or K max regardless of disease stage,” according to the researchers. “In other words, this variable behaves independently and, therefore, can be a valuable tool in monitoring these patients.”

Study limitations include variability in both objective measures and speed among individuals with KC progression and the failure to perform tensile strength measurements or biomechanics.