Dr. Enrique Gambra Profile

Dr. Enrique Gambra

at 2EYES VISION

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Publications (2)

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Proceedings Article | 27 March 2023 Poster

Long-range frequency-domain optical delay line based on a spinning tilted mirror for low-cost ocular biometry

Maria Pilar Urizar, Alberto de Castro, Enrique Gambra, Álvaro de la Peña, Onur Cetinkaya, Susana Marcos, Andrea Curatolo

Proceedings Volume PC12367, PC123671S (2023) https://doi.org/10.1117/12.2652952

KEYWORDS: Mirrors, Optical coherence tomography, Integrated optics, Distance measurement, Surgery, Retina, Prototyping, Optical simulations, Manufacturing, Eye models

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Optical biometers are routinely used to measure intraocular distances in ophthalmic applications such as cataract surgery planning. However, due to their high cost and reduced transportability, access to them is still limited in low-resource and remote settings, where the prevalence of cataract is higher. To increase patients’ access to optical biometry we propose a novel low-cost frequency-domain optical delay line (FDODL) based on a stepper motor spinning a tilted mirror, integrated into a time-domain (TD) optical coherence tomography (OCT) system. Optical simulations of the low-cost FDODL demonstrated its capability of axially scanning different ranges simply by selecting different tilt angles of the spinning mirror with respect to the motor shaft direction, without any changes to the motor itself. Considering off-the-shelf components up to 2-inch in aperture and a tilt of 5 mechanical degrees, the optical pathlength range could reach up to 26.63 mm. A prototype of the low-cost FDODL with a 1.5-degree tilt angle and an A-scan frequency of 10 Hz was experimentally implemented and combined with a TD-OCT system. The scanning capability of the system was characterized to be 7.31 mm, in good agreement with the results of the simulation. The TD-OCT sample arm featured a fixed delay unit with two orthogonally polarized sample beams, focusing on the anterior segment and on the retina, respectively. The intraocular distances of a model eye were measured with the proposed low-cost biometer and found in agreement with the manufacturer’s specs, validating our novel design.

Proceedings Article | 12 September 2021 Presentation + Paper

Optical quality evaluation for active afocal systems

Xoana Barcala, Enrique Gambra, Lucie Sawides, Ivan Martinez-Ibarburu, Victor Rodriguez-Lopez, Carlos Dorronsoro

Proceedings Volume 11871, 118710Q (2021) https://doi.org/10.1117/12.2596921

KEYWORDS: Distortion, Image quality, Eye, Visual optics, Active optics, Visualization, Computer simulations, Lenses

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SimVis Gekko is a novel see-through binocular visual simulator that is based on liquid-membrane tunable lenses (TLs) projected onto the pupil of the eye using a twisted miniaturized 4-f system. Following a temporal multiplexing approach that introduces periodic defocus variations in optical power at 50Hz, the TL generates multifocal images on the retina of the observer, that look static. In this study, the image quality of different tentative designs of SimVis Gekko was evaluated for different optical powers. The full optical system of SimVis Gekko was computer simulated to get the spot size, prismatic shift, angular magnification, and field curvature up to 20° of field of view. An image quality bench was developed to capture and process images through the SimVis Gekko simulator. The system comprises a grayscale camera and a 19- mm focal-length lens with an adjustable diaphragm. A high-resolution screen was placed at one meter with two different targets: (1) a checkerboard, imaged through a 1-mm diaphragm, to measure optical quality, prismatic shift, magnification, and optical distortion; (2) a binary noise, imaged through a 5-mm diaphragm, used to measure the local field curvature and image quality. Images were obtained from 1 to 3D of the TL and automatically analyzed. Theoretical simulations and experimental measurements showed good agreement. Magnification and curvature were the major differences across designs. The last version measured was free of optical distortions with a central curvature-free area with high optical quality. The developed system could guide the assembly and fine adjustment of active afocal optical systems.

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