Computergestützte Analysetechnik und individuelle Modellbildung zur optomechanischen Untersuchung laserbehandelter Augenlinsen

Presbyopia affects everyone from around 45 years of age. A novel treatment method attempts to counteract the age-related hardening of the crystalline lens in its original cause. By applying fs-laser pulses to the inside of the lens (fs-lentotomy), the flexibility of the lens should be restored within a few minutes without the need to surgically open the eye. So far, there is a lack of systematically collected data showing the effects of this treatment on the geometrical and optical properties of the lens during accommodation.

In this work, a laboratory environment is set up which allows optical and mechanical investigations on ex vivo crystalline lenses during simulated accommodation. For this purpose, a measuring system consisting of an accommodation simulator, an optical coherence tomography system and an experimental ray tracing system is developed, evaluated on porcine eyes and finally tested with human donor crystalline lenses. The analysis technique determines the lens topography and the refraction properties in different states of accommodation before and after the laser treatment. Through the development of several software modules, the data collected from measurements is processed for visualization and for further processing into experimental simulations.

An individually created optics simulation allows the reconstruction of the homogeneous equivalent refractive index of the crystalline lens. This can give hints about the age-dependent refractive index gradient within the human lens, which is also reflected in the distribution of the mechanical material properties. Based on the reconstructed lens contour, a three-dimensional finite element model is constructed and the gradual distribution of stiffness is calculated by means of changes in the shape of the lens under different stress states. In the biomechanics simulation, the effects of virtually set cutting geometries can be analyzed and compared with measurement data.

The computer-assisted analysis technique for modeling thus enables the optomechanical investigation of \emph{ex vivo} crystalline lenses during simulated accommodation in the context of presbyopia treatment with fs-laser pulses.