Date of the defence: 18 october 2024 / Degree Awarded: 18 February 2025

Brief summary:

The eye lens is a vital part of vision that can change its shape to help focus on objects at different distances, a process known as accommodation. However, around the age of 50, the lens loses this ability, making it harder to focus on nearby objects, a condition called presbyopia. To develop solutions for restoring accommodation, it’s essential to understand how it works. Observing this process in a living eye is difficult because the lens is located behind the sclera. One feasible solution is modelling using the finite element method, which constructs a model that simulates the accommodative system and the process of accommodation. An accurate model can effectively simulate the physical and optical behaviour of the lens, which requires accurate input parameters. Models in the literature use varying input parameters to construct lens models with different simulation software, and the results obtained can therefore also vary.

In my work, I constructed gradient refractive index lens models at different ages. By controlling the insertion position of the zonules, the material properties of the lens, and the thickness of the capsule, the influence of biological parameters on accommodation was explored. The same models were constructed in different simulation software, and the influence of the software on the simulation results was verified by comparing the results.

The findings show that the insertion position of the zonule and the properties of the lens material significantly affect the stress magnitude of the lens and can also change the optical power of the lens. However, the effects of the capsule thickness on the mechanical and optical properties of the lens are not obvious in all models. Additionally, there are variations between individual lenses. Lenses of different ages, even lenses of different shapes of the same age, have great differences in mechanical and optical behaviour. Software has a subtle effect on the results, which is mainly reflected in the internal stresses of the lens. Therefore, when using the finite element method, it is necessary to understand the differences between individual lenses, the influence of the input parameters and the possible impact of the software.