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P.D. Jaycock, J. Tyrer, L. Lobo, J. Marshall; Pulsed Laser Shearing Interferometry Analysis of Corneal Boimechanics . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2685.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To develop an in vivo system to measure corneal biomechanics using a pulsed laser shearing interferometer, to overcome the problems of mechanical stability in the living cornea. Methods: A shearing interferometer using a 532 nm, 3 mJ per pulse, diode pumped, frequency doubled, single pulsed YAG laser with a pulse duarion of 10 nanoseconds was built to study corneal deformations. Dedicated software allowed analysis of both in-plane and out-of-plane shearing forces in the corneal tissue. Freshly enucleated lamb eyes were trapped in a holder, connnected to a hydraulic manometer and the intraocular pressure was set between 15 and 25 mmHg. The tectonic properties of the cornea were then examined before and after manual microkeratome planar cuts (LSK One, Moria) at depths of 140, 160 and 180 microns. Results: Fringes of high contrast were obtained from the corneal surface. Increasing numbers of fringes were obtained as the intraocular presure was increased from a baseline pressure of 15 mmHg. At 20 mmHg, 9 fringes and at 25 mmHg, 11 fringes were recorded. This correlates with increasing corneal strain. Fringe patterns showed loss of corneal tectonic properties after microkeratome cuts. Conclusions: We demonstrate in principle that pulsed laser interferometry is a useful tool to determine corneal biomechanics in refractive surgery.
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