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Anita Nevyas-Wallace, Harald Patrick Studer, Cynthia J Roberts; Laser Bridge AK: Novel Architecture for Femtosecond Laser Astigmatic Keratotomy - Comparison and Validation of Patient-Specific Computational Modeling. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3922.
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© ARVO (1962-2015); The Authors (2016-present)
Computational modeling of corneal incisions may help in identifying and developing incision architecture to maximize astigmatic effect while minimizing induction of higher order aberrations (HOA). This study validates a patient-specific computational model of a novel astigmatic keratotomy (AK) incision architecture, the Laser Bridge AK, and compares results which this model predicts for Laser Bridge AK with those which it predicts for AK incisions of uniform depth and thickness.
Using finite element modeling, we simulated the novel architecture of Laser Bridge AK in a custom mathematical function which considered corneal incompressibility and nonlinearity, fiber-induced anisotropy, and inhomogeneity, taking into account realistic fiber distribution from x-ray scattering, and recognizing that corneal stroma is denser anteriorly than posteriorly. A 76 year old man underwent phaco/IOL with AK o.s. Using a DuoTrak blade, a 9mm optical zone nasal AK was made 150 microns shallower centrally than at its ends. Incision morphology was measured via Optical Coherence Tomography. Pre-and post-op patient specific Galilei tomography were imported into Optimeyes software. The simulated incisions’ result was calculated with ABAQUS software. Post-operative results were compared to the simulated postoperative model for validation.
The patient’s astigmatism was reduced from 1.75D against the rule to 0.25D with the rule. The simulated outcome was compared with the patient’s postoperative Galilei corneal tomography. The simulated outcome showed a close match to the measured post-operative results. Compared with the model’s predicted outcome for a traditional AK of uniform depth and thickness, the Laser Bridge AK was predicted to have substantially less induced higher order aberrations, as well as greater astigmatic effect.
Patient-Specific Finite Element Modeling of the Laser Bridge AK was validated for the patient modeled. Laser Bridge FS laser AK incision architecture yielded optimal simulation results with less induction of HOA, yet greater astigmatism correction. Future studies include comparing different novel incision architectures.
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