Abstract
Purpose :
A new therapy approach to encounter presbyopia by treating the crystalline lens with patterns of femtosecond (fs) laser pulses is called fs-lentotomy. Its effectiveness of restoring the accommodation amplitude could not yet be systematically investigated in a laboratory environment. We developed an experimental measuring setup, supported by optics and biomechanical simulations, which now allows studying the impact of fs-lentotomy on individual ex vivo crystalline lenses during simulated accommodation, with the goal of predicting the outcoming results.
Methods :
Porcine ex vivo crystalline lenses can be mounted via the ciliary body into a stretching device to simulate different accommodation states while monitoring the occurring forces. A dual optical coherence tomography (OCT) system is used to obtain volume scans of the central anterior and posterior lens surfaces and further geometrical parameters. These surfaces are extracted from the generated data sets by segmentation techniques. The shapes are used to reconstruct the entire lens shape and as input for a finite element model (FEM) to calculate an individual biomechanics model of that lens inside the setup. A scanning laser ray tracing (LRT) system transmits sequentially parallel beams through the crystalline lens onto an observed diffuser in variable distance in order to detect ray angles and impact points. Zernike polynomials are used to reconstruct the wavefront from this data and to estimate visual aberrations. The optical data together with the lens shape serves as input to generate an optics simulation of the individual lens in the setup with the aim of reconstructing the gradient refractive index with optimization methods. Additionally, the crystalline lens can be treated with fs-laser pulses while situated in the setup.
Results :
The experimental setup was successfully tested by a study on porcine crystalline lenses during simulated accommodation, but it can also be used on isolated human lenses. Furthermore, we developed the methodology to generate individual optics and biomechanics simulations of every single lens undergoing fs-lentotomy in our accommodation setup.
Conclusions :
The measurement setup and simulations allow studying ex vivo porcine crystalline lenses during simulated accommodation and support the understanding and effectiveness of fs-lentotomy.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.