Analysis of thermal damage caused by retinal implant in a feline eye

Resumo

The advancement of the technology in the detection of some pathologies has provided several types of treatments that have been studied and applied to humans. Even hereditary diseases with no cure prognosis can be alleviated with the use of implanted devices. This is the case of Retinitis Pigmentosa, which has no cure. However, the use of retinal implants can help in partial recovery of the patient's vision. Several types of treatments have been studied and applied in humans. The present work was developed with the objective of obtaining insights that can help and guide a safe procedure for retinal implantation in patients with Retinitis Pigmentosa. In this process, certain precautions must be taken to avoid thermal damage of the patient's residual vision. Therefore, this work aims to calculate the thermal damage that may occur due to temperature increases as a result of the electrical power dissipated by the implant. To allow the validation of the three-dimensional geometry of the human eye, a previous study of a feline eye model with an epiretinal chip was carried out for which numerical simulation of temperature profiles and the calculation of thermal damage were done. In addition to temperature values, thermal damage is a function that quantifies the degree of cellular denaturation as a function of the power applied to the implant and its use time. Among some results presented, the main one proved that with the continuous application of an electrical power of 36.6 mW, the feline eye presented irreversible thermal damage after 5h12min. Furthermore, even after the implant is turned off, the thermal damage continues to increase, until the entire eye returns to its former thermal equilibrium. With the same methodology, an additional study is being carried out to calculate the advancement of the thermal damage in a human eye submitted to the ARGUS II implant, which was approved by the FDA (Foods and Drugs Administration USA) for use in humans. In this work, the SolidWorks® software was used for three-dimensional geometric modeling of the eyeball, its respective tissues and the epiretinal implant. The Ansys-Fluent® was adopted for simulation of temperature profiles. The calculation of the thermal damage as well as the heat source term due to the blood perfusion were programmed and inserted into the Ansys-Fluent® program, using the Finite Volume Method and unstructured meshes.