Corneal Laser Eye Surgery
Biomechanical Model Calculator
The treatment of high prescriptions in the past has been linked to problems with night vision (due to excess spherical aberration) and the long term safety risks of ectasia due to excessively reduced corneal strength. PRK and LASEK have been proposed to reduce the weakening of the cornea for higher prescriptions but such surface procedures possess their own disadvantages for high myopia corrections. ReLEx SMILE is a keyhole form or corneal laser eye surgery which is less invasive than LASIK and leaves the cornea even stronger than with PRK.
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Mathematical Model to Compare the Relative Tensile Strength of the Cornea After PRK, LASIK, and Small Incision Lenticule Extraction DZ Reinstein, TJ Archer, JB Randleman J Refract Surg. 2013;29(7):454-460.
This model calculates the postoperative tensile strength of the cornea as a percentage of the preoperative tensile strength after PRK, LASIK and SMILE. The model calculates this value for any particular corneal thickness and ablation depth / lenticule thickness as well as flap and cap thicknesses. It is derived from the stromal depth-dependent tensile strength data from Randleman et al (JRS 2008) by calculating the area under the curve for the residual uncut stroma as demonstrated in the figures below for PRK, LASIK and SMILE. As the anterior stroma is stronger than the posterior stroma, SMILE has a biomechanical advantage over both PRK and LASIK as the anterior-most stroma remains intact.