Research Project: Cataract Simulator Diagnostics Device Development Using Computational Holographic Displays
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Contributors
Funders
ID
EC.00160
Authors
Ürey, Hakan
Faculty Member
Publications
Intraocular lens simulator using computational holographic display for cataract patients
(Public Library of Science, 2024) Akyazı, Deniz; Aygün, Uğur; Şahin, Afsun; Ürey, Hakan; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; School of Medicine; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; SCHOOL OF MEDICINE
Purpose To develop and validate a holography based vision simulator for the demonstration of expected postoperative vision corresponding to monofocal and multifocal intraocular lenses (IOL) to cataract patients before surgery.Methods An artificial eye model is used to measure the optical performance of different IOL types. The resultant aberrations and degradations are then modeled using phase holograms and shown to subjects on a holographic display. We measure the contrast and resolution loss, halos around the light sources, and point spread function (PSF) corresponding to three different IOLs. We tested the holography based vision simulator on 13 healthy subjects and 6 cataract patients.Results Monofocal, bifocal, and trifocal IOLs exhibited a contrast decrease of 5%, 42%, and 45% and a resolution limit of 4.49, 4.00, and 4.00 lp/mm (using 0.05 MTF criteria), respectively. Monofocal IOLs have the best resolution and contrast at the optimal focus distance, and multifocal lenses offer extended depth-of-field but exhibit prominent halos and reduced contrast/resolution.Conclusion We confirmed that the visual functions of IOLs could be successfully modeled using phase holograms and simulated using a holographic display without using a physical IOL. Patients can experience the effects of different IOL options prior to surgery, which helps with IOL selection, expectation management, and patient satisfaction.
Wearable multi-color RAPD screening device
(Society of Photo-optical Instrumentation Engineers (SPIE), 2023) Aygün, Uğur; Hasanreisoğlu, Murat; Kavaklı, Koray; Küçüködük, Abdullah; Şahin, Afsun; Ürey, Hakan; Gülersoy, Arda; Tuzcu, Ahmet Berk; Gündüzalp, Doğa; Güleser, Ümit Yaşar; Department of Electrical and Electronics Engineering; School of Medicine; Yes; College of Engineering; SCHOOL OF MEDICINE
In this work, we developed a wearable, head-mounted device that automatically calculates the precise Relative Afferent Pupillary Defect (RAPD) value of a patient. The device consists of two RGB LEDs, two infrared cameras, and one microcontroller. In the RAPD test, the parameters like LED on-off durations, brightness level, and color of the light can be controlled by the user. Upon data acquisition, a computational unit processes the data, calculates the RAPD score and visualizes the test results with a user-friendly interface. Multiprocessing methods used on GUI to optimize the processing pipeline. We have shown that our head-worn instrument is easy to use, fast, and suitable for early-diagnostics and screening purposes for various neurological conditions such as RAPD, glaucoma, asymmetric glaucoma, and anisocoria.
Fabrication and characterization of a 2D PZT MEMS resonant scanner
(Iop Publishing Ltd, 2025) Zolfaghari, Parviz; Khodapanahandeh, Mehrdad; Ürey, Hakan; Khodapanahandeh, Mehrdad; Optical Microsystems Laboratory (MEMS); Graduate School of Sciences and Engineering; Department of Electrical and Electronics Engineering; Yes; Research Center; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; College of Engineering
This work presents the design, simulation, fabrication, and characterization of a novel architectural compact two-dimensional (2D) resonant MEMS scanning mirror actuated by thin-film lead zirconate titanate (PZT). The device employs an innovative mechanically coupled dual-axis architecture fabricated using a three-mask process on an silicon-on-insulator PZT deposited wafer, significantly reducing system complexity while achieving high performance. The scanner integrates a 1 x 1.4 mm oval mirror within a 7 x 4.7 mm die, actuated by PZT thin-film elements optimized for resonant operation at 3.6 kHz (vertical) and 54.2 kHz (horizontal) under 12 Vp-p periodic pulse driving. The system achieves optical scan angles of 4.8 degrees and 11.5 degrees in vertical and horizontal directions, respectively, with quality factors of 750 (vertical) and 1050 (horizontal). These values contribute to high scanning bandwidth-efficiency products of 24.2 degrees mm kHz (vertical) and 623 degrees mm kHz (horizontal), among the higher values reported for 2D PZT-MEMS scanners. Finite element analysis confirmed minimal stress and mirror deformation, and experimental validation demonstrated excellent agreement with simulation results. This architecture demonstrates the feasibility of high-resolution laser scanning, as required in applications such as optical coherence tomography, light detection and ranging, and displays, by achieving performance levels in line with those used in such systems.
Improving defocus blur in holographic displays
(John Wiley and Sons, 2023) Kavaklı, Koray; Ürey, Hakan; Itoh, Yuta; Akşit, Kaan; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
In this paper we present a novel multiplane computer generated hologram calculation approach that enables artifact free and realistic-looking defocus blur for optical reconstructions in a holographic display. We introduce a new targeting method and a loss function that evaluates the focused and defocused parts of the reconstructed images. We demonstrate that our method is applicable to various standard hologram generation routines such for both iterative and non-iterative CGH calculation methods. We also demonstrate our new gradient descent-based optimization with double phase constraint combined with our targeting scheme and loss function provides the best image quality. We validate our findings for both the numerical reconstructions and optical captures that are acquired from our holographic display prototype. © 2023, John Wiley and Sons Inc. All rights reserved.
Dynamic accommodation measurement using Purkinje reflections and machine learning
(Nature Research, 2023) Aygün, Uğur; Özhan, Faik Ozan; Ürey, Hakan; Şahin, Afsun; KUTTAM (Koç University Research Center for Translational Medicine); Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; School of Medicine; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center; SCHOOL OF MEDICINE
Quantifying eye movement is important for diagnosing various neurological and ocular diseases as well as AR/VR displays. We developed a simple setup for real-time dynamic gaze tracking and accommodation measurements based on Purkinje reflections, which are the reflections from front and back surfaces of the cornea and the eye lens. We used an accurate eye model in ZEMAX to simulate the Purkinje reflection positions at different focus distances of the eye, which matched the experimental data. A neural network was trained to simultaneously predict vergence and accommodation using data collected from 9 subjects. We demonstrated that the use of Purkinje reflection coordinates in machine learning resulted in precise estimation. The proposed system accurately predicted the accommodation with an accuracy better than 0.22 D using subject’s own data and 0.40 D using other subjects’ data with two-point calibration in tests performed with 9 subjects in our setup. © 2023, The Author(s).
