Abstract
Purpose: :
As the concentration of amylase is enhanced in keratoconus patients, the aim of the present study was to investigate the effect of amylase on the biomechanical stiffness of the cornea in vitro.
Methods: :
Corneal strips were prepared from 20 fresh enucleated porcine eyes. Ten strips were treated with amylase solution for 48 hours, 10 other strips served as controls. Stress-strain measurements using a microcomputer-controlled biomaterial tester (MiniMat; Rheonetric Scientific GmbH, Benshaim, Germany) were performed to determine the stiffness of the corneal strips.
Results: :
In contrast to the control corneas, the amylase treated corneas showed a reduced corneal thickness (CCT = 632.1±59.6 µm, P=0.0001). At 10 % strain the stress in the control group was 213.4± 53.1 kPa and in the amylase group 96.5±27.0 kPa which was statistically significantly different between both groups (P=0.0001). The Young’s modulus in the control group was 3.8 MPa and in the amylase group 2.2 MPa.
Conclusions: :
The present study showed a reduction of the corneal stiffness by the effect of amylase leading to a dissolving of the ground substance from the stroma. It is the first study showing the influence of the ground substance on the biomechanical properties of the cornea. As the amount of amylase in the lacrimal gland is enhanced in keratoconus, the reduced corneal stiffness might contribute to the pathogenesis of keratoconus.
Keywords: cornea: basic science • keratoconus • enzymes/enzyme inhibitors