Interferometric technique to measure biomechanical changes in the cornea induced by refractive surgery

PURPOSE: To develop a technique to quantify biomechanical changes in the cornea after microkeratome incisions as would be performed in laser in situ keratomileusis. SETTING: St Thomas' Hospital, London, and the Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, United Kingdom. METHODS: Corneal displacements of whole sheep eyes were studied under hydrostatic loading using electronic speckle pattern interferometry before and after microkeratome incisions. RESULTS: After hydrostatic loading, there was a 20.7% increase in corneal displacement in corneas with microkeratome incisions compared to unoperated corneas; this was statistically significant (P=.0068, unpaired t test). CONCLUSIONS: Results show that in the formation of the microkeratome flap, collagen fibers are severed and minimal biomechanical loading is distributed through the flap. Corneal biomechanical integrity is compromised after microkeratome incisions.