Researchers from New Zealand challenge the longstanding concept that the corneal epithelium plays an insigniﬁcant role in corneal biomechanics after noting signiﬁcant alterations in these parameters after epithelium removal for corneal crosslinking (CXL). They found that epithelial debridement seems to alter corneal integrity and make the cornea more prone to deformation.
In their study, the researchers used an ultrahigh-speed Scheimpﬂug camera equipped with a non-contact tonometer to analyze the in vivo biomechanical effect of the corneal epithelial removal in keratoconic eyes undergoing CXL.
The comparative analysis of 45 eyes demonstrated a signiﬁcant alteration to corneal stiffness after epithelial removal. The cornea was 23.7±15.7μm thinner after epithelial removal, and it was more deeply deformed after the air puff test. The team noted reduced corneal stiffness after epithelial removal using several parameters.
While the researchers do not fully understand the reasons for the reduction in biomechanical integrity, they believe the changes are unrelated to biochemical changes or to a wound healing response in the cornea after epithelial removal since the measurements before and after epithelial removal were taken only minutes apart.
“We hypothesize that corneal epithelial debridement may lead to changes in the anterior stromal collagen arrangement because a proportion of anterior lamellae insert directly into Bowman layer, and this subsequently leads to a measurable reduction in corneal stiffness,” the researchers concluded in their paper.
|Ziaei M, Gokul A, Vellara H, et al. Measurement of in vivo biomechanical changes attributable to epithelial removal in keratoconus using a noncontact tonometer. Cornea. April 29, 2020. [Epub ahead of print].|