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Mechanical Simulation of Corneal Ring Implant Surgery for Keratoconus Treatment

Bagheri Tadi, Hamid Reza | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52769 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Asghari, Mohsen
  7. Abstract:
  8. Keratoconus is a progressive disease in which the cornea becomes thin and due to the presence of internal pressure in the eye and its application to the cornea, the cornea becomes bulging and conical. In recent years, due to the relatively large number of patients with keratoconus and also the ability of this disease to progress over time, the need to study and research on the treatment of this disease is noticeable. Early and non-surgical methods for the treatment of keratocous are use glass and contact lenses, but since the disease is progressive and usually appears more severely over time, ophthalmologists use the method of corneal ring implant for treatment.In this study, 9 types of ring implants with different dimensions inside the cornea were simulated on a patient in the ABAQUS finite element software and finally the optimal ring geometry was obtained to treat that patient. To simulate, the geometry of the cornea is obtained from data scanned by ophthalmologists. The cornea is considered to be a hyperelastic substance with Neo-Hookean behavior, the coefficients of which have been obtained according to the data in previous researches. Also, the ring itself is not modeled and instead a groove with a triangular surface and 0.6 mm width (like the width of the ring) and a very low height (0.01 mm) inside the cornea is considered and then the location of the groove points, used to open the groove surface equal to size of the ring surface. Finally, using MATLAB software and with the help of Genetic algorithm method, the Zernike coefficients obtained for the outer surface of the cornea after simulation and with the help of which the quality of the patient's vision has been determined. Finally, by selecting the appropriate ring for the patient, the Cyl and Sph power parameters related to the patient's vision have improved by 1.05 and 0.4 diopters, respectively, compared to ophthalmic surgery.In order to validate the results of this study, the results were compared with the postoperative data of ophthalmologists
  9. Keywords:
  10. Keratocanic Corneas ; Hyperelasticity ; Finite Element Simulation ; Zernike Coefficients

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