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The estimation of intraocular pressure after refractive surgery. Statistical and simulation data
Author(s) -
BAUER SM,
KACHANOV AB,
SEMENOV BN
Publication year - 2008
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2008.4355.x
Subject(s) - cornea , refractive surgery , intraocular pressure , ophthalmology , sclera , lasik , medicine , materials science , optometry
Purpose To estimate the change in intraocular pressure (IOP) measured by either Maklakov tonometer or by Goldmann tonometer after refractive surgery for myopia and hypermetropia. In contrast to Goldmann tonometer, which measures the IOP by estimating the force needed to apply for prescribed deformation of the cornea, with Maklakov tonometer IOP is measured by estimating the diameter of the circular contact area of the cornea and the flat bottom of a tonometer. Methods Numerical simulations have been carried out using finite element package ANSYS. The eye shell is modeled as two joint shells (cornea and sclera) with different mechanical properties. The results of mechanical simulation and statistical data were compared. For statistics the measurements of IOP were made for both eyes of 110 patients before and one month after corneal refractive surgery Results Applanation tonometry after refractive surgery for both myopia and hypermetropia shows reduction of IOP, since in both cases the bending stiffness of the cornea decreases. For some parameters of refractive surgery for myopia (with decreasing corneal thickness less than 0.1 mm) the reduction of IOP is correlated with central corneal thickness. But in general the current model predicts nonlinear relations between new central corneal thickness and IOP reading Conclusion All parameters of refractive surgery (the depth, the width and the place of ablation, the thickness of flap for Lasik surgery) have an effect on IOP reading obtained with both Goldmann and Maklakov tonometry. The results obtained by Goldmann tonometer are significantly more sensitive to all parameters of refractive surgery than those found with the Maklakov tonometer with load 10 g.