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Multifocal intraocular lenses incorporate a variety of design considerations, including dimensioning of the base monofocal shape and the diffraction grating. While studying three different lens models, we present a practical approach for mathematical modelling and evaluation of these geometries. Contrary to typical lens measurement methods, non-contact measurements were performed on the Alcon SN6AD1, HumanOptics MS 612 DAY and the AMO ZMA00 lenses using a confocal microscope. Subsequent data processing includes centering, tilting correction, filtering and an algorithmic decomposition into a conic and polynomial part and the diffraction grating. Lastly, evaluation of fitting parameters and grating shape is done to allow for inferences about further optical properties. Results and analysis show the confocal microscope to be a suitable imaging method for lens measurements. The processing of this data enables the reconstruction of the annular diffraction grating over the complete lens diameter. Apodization, near addition and diffraction efficiency characteristics are found utilizing the grating shape. Additionally, near-optical axis curvature, asphericity and higher order polynomials are identified qualitatively from the reconstruction of the monofocal base form. Derived properties also include the lens optical base and addition power. By making use of the surface geometries, as well as the lens’ material and thickness, a full lens model can be created for further studies. In summary, our analytical approach enables the insight to various intraocular lens design decisions. Furthermore, this procedure is suitable for lens model creation for research and simulation.
This project, which is funded by the German Federal Ministry of Education and Research, attempts to improve the accessibility of diagnostic instruments for glaucoma screening. The presented approach aims to realize real-time near-infrared video fundus imaging that enables the use of targeted fixation stimuli to ensure continuous imaging. The integration of near-infrared illumination with a wavelength of 780 nm not only avoids pupil constriction, but also enables mesopic imaging in darkened ambient light, ensuring optimal visualization of the retinal structure. This innovative system achieves nearly reflection-free imaging through polarized illumination with polarization-dependent beam paths. Its primary aim is to capture extensive fundus areas to facilitate correlations with linear optical coherence tomography (LOCT) measurements. In the future, the fundus setup will be integrated into the LOCT setup. In this research project, the primary aim is to generate images of the optic nerve, but it is also possible to carry out examinations of the macula. Unlike from traditional fundus cameras, this system has a controllable screen for generating individual fixation stimuli, which creates continuous eye movements and enables controlled imaging. The main objective is to capture large fundus areas and track eye positions to combine this information with the LOCT measurements A-scan positions, which enables the creation of B-scans with irregular geometries. This approach replaces the need for complex scanning systems by leveraging natural eye movements. The approach can thus be used to detect retinal pathologies in a different way and could therefore be used for more comprehensive diagnostic and scientific applications.
Development of a Linear Optical Coherence Tomography Low-Cost System for Ophthalmic Applications
(2024)
This publication introduces a prototype of a fiber-based linear optical coherence tomography system (LOCT) that can be used for economical retinal screening in ophthalmology. The system uses standard off-the-shelf components to reduce production costs, complexity, and adjustment efforts while providing high-quality imaging of artificial retinal structures. We present the results of A- and B-scans of technical samples and an artificial eye model that was conducted to assess the system’s performance regarding axial resolution, imaging depth, and dispersion compensation. The study’s findings suggest that LOCT is a cost-effective solution for ophthalmology and shows great potential for monitoring the progression of retina-related diseases such as glaucoma or age-related macular degeneration.
Purpose: To evaluate the differences between two extended depth-of-focus intraocular lenses, the Alcon IQ Vivity and the Bausch & Lomb LuxSmart and to compare them with a simple monofocal lens, the Alcon IQ, using a simulation-based approach.
Methods: A mathematical lens model was created for each lens type based on a measured surface geometry. The lens model was then used in a raytracer to calculate a refractive power map of the lens and a ray propagation image for the focal zone.
Results: The simulations confirm the enhanced depth of focus of these two lenses. There are apparent differences between the models. For the Vivity, more light is directed into the far focus in low light conditions, whereas the LuxSmart behaves more pupil independent and prioritizes intermediate vision.
Conclusions: The simulation-based approach was effective in evaluating and comparing the design aspects of these lenses. It can be positioned as a valuable third tool for lens characterization, complementing in vivo studies and in vitro measurements.
Translational Relevance: With this approach not only focusing on the resulting optical performance, but the underlying functional mechanisms, it paves the way forward for a better adaptation to the individual needs and preferences of patients.