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Kaushik V, Dąbrowski M, Gessa L, Kumar N, Fernandes H. Two-photon excitation fluorescence in ophthalmology: safety and improved imaging for functional diagnostics. Front Med (Lausanne) 2024; 10:1293640. [PMID: 38235268 PMCID: PMC10791900 DOI: 10.3389/fmed.2023.1293640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 12/11/2023] [Indexed: 01/19/2024] Open
Abstract
Two-photon excitation fluorescence (TPEF) is emerging as a powerful imaging technique with superior penetration power in scattering media, allowing for functional imaging of biological tissues at a subcellular level. TPEF is commonly used in cancer diagnostics, as it enables the direct observation of metabolism within living cells. The technique is now widely used in various medical fields, including ophthalmology. The eye is a complex and delicate organ with multiple layers of different cell types and tissues. Although this structure is ideal for visual perception, it generates aberrations in TPEF eye imaging. However, adaptive optics can now compensate for these aberrations, allowing for improved imaging of the eyes of animal models for human diseases. The eye is naturally built to filter out harmful wavelengths, but these wavelengths can be mimicked and thereby utilized in diagnostics via two-photon (2Ph) excitation. Recent advances in laser-source manufacturing have made it possible to minimize the exposure of in vivo measurements within safety, while achieving sufficient signals to detect for functional images, making TPEF a viable option for human application. This review explores recent advances in wavefront-distortion correction in animal models and the safety of use of TPEF on human subjects, both of which make TPEF a potentially powerful tool for ophthalmological diagnostics.
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Affiliation(s)
- Vineeta Kaushik
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Michał Dąbrowski
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
- International Centre for Translational Eye Research, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Luca Gessa
- International Centre for Translational Eye Research, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Nelam Kumar
- International Centre for Translational Eye Research, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Humberto Fernandes
- International Centre for Translational Eye Research, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
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Palczewska G, Wojtkowski M, Palczewski K. From mouse to human: Accessing the biochemistry of vision in vivo by two-photon excitation. Prog Retin Eye Res 2023; 93:101170. [PMID: 36787681 PMCID: PMC10463242 DOI: 10.1016/j.preteyeres.2023.101170] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 02/03/2023] [Accepted: 02/06/2023] [Indexed: 02/13/2023]
Abstract
The eye is an ideal organ for imaging by a multi-photon excitation approach, because ocular tissues such as the sclera, cornea, lens and neurosensory retina, are highly transparent to infrared (IR) light. The interface between the retina and the retinal pigment epithelium (RPE) is especially informative, because it reflects the health of the visual (retinoid) cycle and its changes in response to external stress, genetic manipulations, and drug treatments. Vitamin A-derived retinoids, like retinyl esters, are natural fluorophores that respond to multi-photon excitation with near IR light, bypassing the filter-like properties of the cornea, lens, and macular pigments. Also, during natural aging some retinoids form bisretinoids, like diretinoid-pyridiniumethanolamine (A2E), that are highly fluorescent. These bisretinoids appear to be elevated concurrently with aging. Vitamin A-derived retinoids and bisretinoidss are detected by two-photon ophthalmoscopy (2PO), using a new class of light sources with adjustable spatial, temporal, and spectral properties. Furthermore, the two-photon (2P) absorption of IR light by the visual pigments in rod and cone photoreceptors can initiate visual transduction by cis-trans isomerization of retinal, enabling parallel functional studies. Recently we overcame concerns about safety, data interpretation and complexity of the 2P-based instrumentation, the major roadblocks toward advancing this modality to the clinic. These imaging and retina-function assessment advancements have enabled us to conduct the first 2P studies with humans.
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Affiliation(s)
- Grazyna Palczewska
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA, USA; International Center for Translational Eye Research, Polish Academy of Sciences, Warsaw, Poland; Polgenix, Inc., Department of Medical Devices, Cleveland, OH, USA; Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.
| | - Maciej Wojtkowski
- International Center for Translational Eye Research, Polish Academy of Sciences, Warsaw, Poland; Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland; Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland.
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA, USA; Department of Physiology & Biophysics, School of Medicine, And Chemistry, Molecular Biology and Biochemistry, University of California, Irvine, CA, USA.
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Fluorescence Angiography with Dual Fluorescence for the Early Detection and Longitudinal Quantitation of Vascular Leakage in Retinopathy. Biomedicines 2023; 11:biomedicines11020293. [PMID: 36830829 PMCID: PMC9953145 DOI: 10.3390/biomedicines11020293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/03/2023] [Accepted: 01/18/2023] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Diabetic retinopathy (DR) afflicts more than 93 million people worldwide and is a leading cause of vision loss in working adults. While DR therapies are available, early DR development may go undetected without treatment due to the lack of sufficiently sensitive tools. Therefore, early detection is critically important to enable efficient treatment before progression to vision-threatening complications. A major clinical manifestation of early DR is retinal vascular leakage that may progress from diffuse to more localized focal leakage, leading to increased retinal thickness and diabetic macular edema (DME). In preclinical research, a hallmark of DR in mouse models is diffuse retinal leakage without increased thickness or DME, which limits the utility of optical coherence tomography and fluorescein angiography (FA) for early detection. The Evans blue assay detects diffuse leakage but requires euthanasia, which precludes longitudinal studies in the same animals. METHODS We developed a new modality of ratiometric fluorescence angiography with dual fluorescence (FA-DF) to reliably detect and longitudinally quantify diffuse retinal vascular leakage in mouse models of induced and spontaneous DR. RESULTS These studies demonstrated the feasibility and sensitivity of FA-DF in detecting and quantifying retinal vascular leakage in the same mice over time during DR progression in association with chronic hyperglycemia and age. CONCLUSIONS These proof-of-concept studies demonstrated the promise of FA-DF as a minimally invasive method to quantify DR leakage in preclinical mouse models longitudinally.
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Hong S, Lee J, Moon J, Kong E, Jeon J, Kim YS, Kim HR, Kim P. Intravital longitudinal cellular visualization of oral mucosa in a murine model based on rotatory side-view confocal endomicroscopy. BIOMEDICAL OPTICS EXPRESS 2022; 13:4160-4174. [PMID: 36032579 PMCID: PMC9408257 DOI: 10.1364/boe.462269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/21/2022] [Accepted: 06/25/2022] [Indexed: 06/15/2023]
Abstract
Oral mucosa is a soft tissue lining the inside of the mouth, protecting the oral cavity from microbiological insults. The mucosal immune system is composed of diverse types of cells that defend against a wide range of pathogens. The pathophysiology of various oral mucosal diseases has been studied mostly by ex vivo histological analysis of harvested specimens. However, to analyze dynamic cellular processes in the oral mucosa, longitudinal in vivo observation of the oral mucosa in a single mouse during pathogenesis is a highly desirable and efficient approach. Herein, by utilizing micro GRIN lens-based rotatory side-view confocal endomicroscopy, we demonstrated non-invasive longitudinal cellular-level in vivo imaging of the oral mucosa, visualizing fluorescently labeled cells including various immune cells, pericytes, nerve cells, and lymphatic and vascular endothelial cells. With rotational and sliding movement of the side-view endomicroscope on the oral mucosa, we successfully achieved a multi-color wide-area cellular-level visualization in a noninvasive manner. By using a transgenic mouse expressing photoconvertible protein, Kaede, we achieved longitudinal repetitive imaging of the same microscopic area in the buccal mucosa of a single mouse for up to 10 days. Finally, we performed longitudinal intravital visualization of the oral mucosa in a DNFB-derived oral contact allergy mouse model, which revealed highly dynamic spatiotemporal changes of CSF1R or LysM expressing immune cells such as monocytes, macrophages, and granulocytes in response to allergic challenge for one week. This technique can be a useful tool to investigate the complex pathophysiology of oral mucosal diseases.
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Affiliation(s)
- Sujung Hong
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- KI for Health Science and Technology (KIHST), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Jingu Lee
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- KI for Health Science and Technology (KIHST), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Jieun Moon
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- KI for Health Science and Technology (KIHST), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Eunji Kong
- KI for Health Science and Technology (KIHST), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Jehwi Jeon
- KI for Health Science and Technology (KIHST), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Yeon soo Kim
- Department of Otorhinolaryngology, Konyang University College of Medicine, Konyang University Hospital, Daejeon, 35365, Republic of Korea
| | - Hyung-Ryong Kim
- Department of Pharmacology, College of Dentistry, Jeonbuk National University, Jeonju, 54896, Republic of Korea
| | - Pilhan Kim
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- KI for Health Science and Technology (KIHST), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
- Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
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Schultz R, Schwanengel L, Klemm M, Meller D, Hammer M. Spectral fundus autofluorescence peak emission wavelength in ageing and AMD. Acta Ophthalmol 2021; 100:e1223-e1231. [PMID: 34850573 DOI: 10.1111/aos.15070] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 10/26/2021] [Accepted: 11/19/2021] [Indexed: 01/18/2023]
Abstract
PURPOSE To investigate the spectral characteristics of fundus autofluorescence (FAF) in AMD patients and controls. METHODS Fundus autofluorescence spectral characteristics was described by the peak emission wavelength (PEW) of the spectra. Peak emission wavelength (PEW) was derived from the ratio of FAF recordings in two spectral channels at 500-560 nm and 560-720 nm by fluorescence lifetime imaging ophthalmoscopy. The ratio of FAF intensity in both channels was related to PEW by a calibration procedure. Peak emission wavelength (PEW) measurements were done in 44 young (mean age: 24.0 ± 3.8 years) and 18 elderly (mean age: 67.5 ± 10.2 years) healthy subjects as well as 63 patients with AMD (mean age: 74.0 ± 7.3 years) in each pixel of a 30° imaging field. The values were averaged over the central area, the inner and the outer ring of the ETDRS grid. RESULTS There was no significant difference between PEW in young and elderly controls. However, PEW was significantly shorter in AMD patients (ETDRS grid centre: 571 ± 26 nm versus 599 ± 17 nm for elderly controls, inner ring: 596 ± 17 nm versus 611 ± 11 nm, outer ring: 602 ± 16 nm versus 614 ± 11 nm). After a mean follow-up time of 50.8 ± 10.8 months, the PEW in the patients decreased significantly by 9 ± 19 nm in the inner ring of the grid. Patients, showing progression to atrophic AMD in the follow up, had significantly (p ≤ 0.018) shorter PEW at baseline than non-progressing patients. CONCLUSIONS Peak emission wavelength (PEW) is related to AMD pathology and might be a diagnostic marker in AMD. Possibly, a short PEW can predict progression to retinal and/or pigment epithelium atrophy.
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Affiliation(s)
- Rowena Schultz
- Department of Ophthalmology University Hospital Jena Jena Germany
| | | | - Matthias Klemm
- Institute of Biomedical Engineering and Informatics Technical Univ. Ilmenau Ilmenau Germany
| | - Daniel Meller
- Department of Ophthalmology University Hospital Jena Jena Germany
| | - Martin Hammer
- Department of Ophthalmology University Hospital Jena Jena Germany
- Center for Medical Optics and Photonics Univ. of Jena Jena Germany
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Qin Z, He S, Yang C, Yung JSY, Chen C, Leung CKS, Liu K, Qu JY. Adaptive optics two-photon microscopy enables near-diffraction-limited and functional retinal imaging in vivo. LIGHT, SCIENCE & APPLICATIONS 2020; 9:79. [PMID: 32411364 PMCID: PMC7203252 DOI: 10.1038/s41377-020-0317-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/11/2020] [Accepted: 04/15/2020] [Indexed: 05/08/2023]
Abstract
In vivo fundus imaging offers non-invasive access to neuron structures and biochemical processes in the retina. However, optical aberrations of the eye degrade the imaging resolution and prevent visualization of subcellular retinal structures. We developed an adaptive optics two-photon excitation fluorescence microscopy (AO-TPEFM) system to correct ocular aberrations based on a nonlinear fluorescent guide star and achieved subcellular resolution for in vivo fluorescence imaging of the mouse retina. With accurate wavefront sensing and rapid aberration correction, AO-TPEFM permits structural and functional imaging of the mouse retina with submicron resolution. Specifically, simultaneous functional calcium imaging of neuronal somas and dendrites was demonstrated. Moreover, the time-lapse morphological alteration and dynamics of microglia were characterized in a mouse model of retinal disorder. In addition, precise laser axotomy was achieved, and degeneration of retinal nerve fibres was studied. This high-resolution AO-TPEFM is a promising tool for non-invasive retinal imaging and can facilitate the understanding of a variety of eye diseases as well as neurodegenerative disorders in the central nervous system.
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Affiliation(s)
- Zhongya Qin
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Sicong He
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Chao Yang
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Jasmine Sum-Yee Yung
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Congping Chen
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | | | - Kai Liu
- Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
- State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
- Center of Systems Biology and Human Health, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Jianan Y. Qu
- Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
- State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
- Center of Systems Biology and Human Health, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Wahl DJ, Ju MJ, Jian Y, Sarunic MV. Non-invasive cellular-resolution retinal imaging with two-photon excited fluorescence. BIOMEDICAL OPTICS EXPRESS 2019; 10:4859-4873. [PMID: 31565530 PMCID: PMC6757458 DOI: 10.1364/boe.10.004859] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/13/2019] [Accepted: 08/13/2019] [Indexed: 05/02/2023]
Abstract
Two-photon excited fluorescence (TPEF) imaging of the retina is a developing technique that provides non-invasive compound-specific measurements from the retina. In this report, we demonstrate high-resolution TPEF imaging of the mouse retina using sensorless adaptive optics (SAO) and optical coherence tomography (OCT). A single near-infrared light source was used for simultaneous multi-modal imaging with OCT and TPEF. The image-based SAO could be performed using the en face OCT or the TPEF for aberration correction. Our results demonstrate OCT and TPEF for angiography. Also, we demonstrate non-invasive cellular-resolution imaging of fluorescently labelled cells and the Retinal Pigment Epithelium (RPE) mosaic.
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Affiliation(s)
- Daniel J. Wahl
- Engineering Science, Simon Fraser University, Burnaby, BC, Canada
| | - Myeong Jin Ju
- Engineering Science, Simon Fraser University, Burnaby, BC, Canada
| | - Yifan Jian
- Engineering Science, Simon Fraser University, Burnaby, BC, Canada
- Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA
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Jayabalan GS, Bille JF, Mao XW, Gimbel HV, Rauser ME, Wenz F, Fan JT. Retinal safety evaluation of two-photon laser scanning in rats. BIOMEDICAL OPTICS EXPRESS 2019; 10:3217-3231. [PMID: 31467775 PMCID: PMC6706040 DOI: 10.1364/boe.10.003217] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 05/10/2019] [Indexed: 05/03/2023]
Abstract
Safe use of retinal imaging with two-photon excitation in human eyes is crucial, as the effects of ultrashort pulsed lasers on the retina are relatively unknown. At the time of the study, the laser safety standards were inadequate due to the lack of biological data. This article addresses the feasibility of two-photon retinal imaging with respect to laser safety. In this study, rat retinas were evaluated at various laser exposure levels and with different laser parameters to determine the effects of laser-induced optical damage. The results were experimentally verified using confocal reflectance imaging, two-photon fluorescein angiography, immunohistochemistry, and correlated to the IEC 60825-1 laser safety standard.
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Affiliation(s)
- Gopal Swamy Jayabalan
- Clinic for Radiotherapy and Radiation Oncology, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany
- Loma Linda University Eye Institute, Loma Linda, CA 92354, USA
| | - Josef F. Bille
- Clinic for Radiotherapy and Radiation Oncology, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany
| | - Xiao Wen Mao
- Department of basic sciences, Loma Linda University, CA 92350, USA
| | | | | | - Frederik Wenz
- Clinic for Radiotherapy and Radiation Oncology, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany
| | - Joseph T. Fan
- Loma Linda University Eye Institute, Loma Linda, CA 92354, USA
- Department of basic sciences, Loma Linda University, CA 92350, USA
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Noninvasive Two-Photon Microscopy Imaging of Mouse Retina and Retinal Pigment Epithelium. Methods Mol Biol 2019; 1834:333-343. [PMID: 30324453 DOI: 10.1007/978-1-4939-8669-9_21] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Two-photon excitation microscopy is perfectly suited for imaging deep into the retina due to its use of infrared (IR) wavelengths to excite endogenous fluorophores such as vitamin A-derived retinoids present in this tissue. Furthermore, two-photon excitation occurs only around a small focal volume, and scattered IR photons cannot excite retinal chromophores. These characteristics contribute to subcellular resolution and low noise of images obtained from deep within retinal layers. Here we describe how to customize a two-photon microscope for noninvasive imaging of the retina and retinal pigment epithelium (RPE) in the mouse eye, along with detailed instructions for mouse handling and retinal imaging, and we provide examples of mouse retinal two-photon microscopy data.
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Şencan İ, Esipova TV, Yaseen MA, Fu B, Boas DA, Vinogradov SA, Shahidi M, Sakadžić S. Two-photon phosphorescence lifetime microscopy of retinal capillary plexus oxygenation in mice. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-9. [PMID: 30516039 PMCID: PMC6278707 DOI: 10.1117/1.jbo.23.12.126501] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 11/07/2018] [Indexed: 05/23/2023]
Abstract
Impaired oxygen delivery and/or consumption in the retinal tissue underlies the pathophysiology of many retinal diseases. However, the essential tools for measuring oxygen concentration in retinal capillaries and studying oxygen transport to retinal tissue are still lacking. We show that two-photon phosphorescence lifetime microscopy can be used to map absolute partial pressures of oxygen (pO2) in the retinal capillary plexus. Measurements were performed at various retinal depths in anesthetized mice under systemic normoxic and hyperoxic conditions. We used a newly developed two-photon phosphorescent oxygen probe, based on a two-photon absorbing platinum tetraphthalimidoporphyrin, and commercially available optics without correction for optical aberrations of the eye. The transverse and axial distances within the tissue volume were calibrated using a model of the eye's optical system. We believe this is the first demonstration of in vivo depth-resolved imaging of pO2 in retinal capillaries. Application of this method has the potential to advance our understanding of oxygen delivery on the microvascular scale and help elucidate mechanisms underlying various retinal diseases.
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Affiliation(s)
- İkbal Şencan
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Tatiana V. Esipova
- University of Pennsylvania, Departments of Biochemistry and Biophysics and of Chemistry, Philadelphia, Pennsylvania, United States
| | - Mohammad A. Yaseen
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - Buyin Fu
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
| | - David A. Boas
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
- Boston University, Department of Biomedical Engineering, Boston, Massachusetts, United States
| | - Sergei A. Vinogradov
- University of Pennsylvania, Departments of Biochemistry and Biophysics and of Chemistry, Philadelphia, Pennsylvania, United States
| | - Mahnaz Shahidi
- University of Southern California, Departments of Ophthalmology and Biomedical Engineering, Los Angeles, California, United States
| | - Sava Sakadžić
- Massachusetts General Hospital, Harvard Medical School, Athinuola A. Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown, Massachusetts, United States
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Palczewska G, Stremplewski P, Suh S, Alexander N, Salom D, Dong Z, Ruminski D, Choi EH, Sears AE, Kern TS, Wojtkowski M, Palczewski K. Two-photon imaging of the mammalian retina with ultrafast pulsing laser. JCI Insight 2018; 3:121555. [PMID: 30185665 DOI: 10.1172/jci.insight.121555] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 07/24/2018] [Indexed: 12/13/2022] Open
Abstract
Noninvasive imaging of visual system components in vivo is critical for understanding the causal mechanisms of retinal diseases and for developing therapies for their treatment. However, ultraviolet light needed to excite endogenous fluorophores that participate in metabolic processes of the retina is highly attenuated by the anterior segment of the human eye. In contrast, 2-photon excitation fluorescence imaging with pulsed infrared light overcomes this obstacle. Reducing retinal exposure to laser radiation remains a major barrier in advancing this technology to studies in humans. To increase fluorescence intensity and reduce the requisite laser power, we modulated ultrashort laser pulses with high-order dispersion compensation and applied sensorless adaptive optics and custom image recovery software and observed an over 300% increase in fluorescence of endogenous retinal fluorophores when laser pulses were shortened from 75 fs to 20 fs. No functional or structural changes to the retina were detected after exposure to 2-photon excitation imaging light with 20-fs pulses. Moreover, wide bandwidth associated with short pulses enables excitation of multiple fluorophores with different absorption spectra and thus can provide information about their relative changes and intracellular distribution. These data constitute a substantial advancement for safe 2-photon fluorescence imaging of the human eye.
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Affiliation(s)
| | - Patrycjusz Stremplewski
- Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Susie Suh
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Nathan Alexander
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - David Salom
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Zhiqian Dong
- Polgenix, Inc., Department of Medical Devices, Cleveland, Ohio, USA
| | - Daniel Ruminski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Elliot H Choi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Avery E Sears
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Timothy S Kern
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Maciej Wojtkowski
- Department of Physical Chemistry of Biological Systems, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
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In vivo two-photon imaging of retina in rabbits and rats. Exp Eye Res 2018; 166:40-48. [DOI: 10.1016/j.exer.2017.04.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 04/25/2017] [Accepted: 04/25/2017] [Indexed: 11/21/2022]
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13
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Zhang L, Song W, Shao D, Zhang S, Desai M, Ness S, Roy S, Yi J. Volumetric fluorescence retinal imaging in vivo over a 30-degree field of view by oblique scanning laser ophthalmoscopy (oSLO). BIOMEDICAL OPTICS EXPRESS 2018; 9:25-40. [PMID: 29359085 PMCID: PMC5772579 DOI: 10.1364/boe.9.000025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 11/24/2017] [Accepted: 11/25/2017] [Indexed: 05/03/2023]
Abstract
While fluorescent contrast is widely used in ophthalmology, three-dimensional (3D) fluorescence retinal imaging over a large field of view (FOV) has been challenging. In this paper, we describe a novel oblique scanning laser ophthalmoscopy (oSLO) technique that provides 3D volumetric fluorescence retinal imaging with only one raster scan. The technique utilizes scanned oblique illumination and angled detection to obtain fluorescent cross-sectional images, analogous to optical coherence tomography (OCT) line scans (or B-scans). By breaking the coaxial optical alignment used in conventional retinal imaging modalities, depth resolution is drastically improved. To demonstrate the capability of oSLO, we have performed in vivo volumetric fluorescein angiography (FA) of the rat retina with ~25μm depth resolution and over a 30° FOV. Using depth segmentation, oSLO can obtain high contrast images of the microvasculature down to single capillaries in 3D. The multi-modal nature of oSLO also allows for seamless combination with simultaneous OCT angiography.
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Affiliation(s)
- Lei Zhang
- Department of Medicine, Boston University School of Medicine, Boston MA, 02118, USA
- These authors contributed equally to this work
| | - Weiye Song
- Department of Medicine, Boston University School of Medicine, Boston MA, 02118, USA
- These authors contributed equally to this work
| | - Di Shao
- Department of Medicine, Boston University School of Medicine, Boston MA, 02118, USA
| | - Sui Zhang
- Danna-Farber Cancer Institute, Boston MA, 02215, USA
| | - Manishi Desai
- Department of Ophthalmology, Boston University School of Medicine, Boston MA, 02118, USA
| | - Steven Ness
- Department of Ophthalmology, Boston University School of Medicine, Boston MA, 02118, USA
| | - Sayon Roy
- Department of Medicine, Boston University School of Medicine, Boston MA, 02118, USA
- Department of Ophthalmology, Boston University School of Medicine, Boston MA, 02118, USA
| | - Ji Yi
- Department of Medicine, Boston University School of Medicine, Boston MA, 02118, USA
- Center of Regenerative Medicine, Boston University, Boston, MA, 02118, USA
- Boston University Photonics Center, Boston MA, 02215, USA
- These authors contributed equally to this work
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14
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Bremer D, Pache F, Günther R, Hornow J, Andresen V, Leben R, Mothes R, Zimmermann H, Brandt AU, Paul F, Hauser AE, Radbruch H, Niesner R. Longitudinal Intravital Imaging of the Retina Reveals Long-term Dynamics of Immune Infiltration and Its Effects on the Glial Network in Experimental Autoimmune Uveoretinitis, without Evident Signs of Neuronal Dysfunction in the Ganglion Cell Layer. Front Immunol 2016; 7:642. [PMID: 28066446 PMCID: PMC5179567 DOI: 10.3389/fimmu.2016.00642] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 12/13/2016] [Indexed: 12/12/2022] Open
Abstract
A hallmark of autoimmune retinal inflammation is the infiltration of the retina with cells of the innate and adaptive immune system, leading to detachment of the retinal layers and even to complete loss of the retinal photoreceptor layer. As the only optical system in the organism, the eye enables non-invasive longitudinal imaging studies of these local autoimmune processes and of their effects on the target tissue. Moreover, as a window to the central nervous system (CNS), the eye also reflects general neuroinflammatory processes taking place at various sites within the CNS. Histological studies in murine neuroinflammatory models, such as experimental autoimmune uveoretinitis (EAU) and experimental autoimmune encephalomyelitis, indicate that immune infiltration is initialized by effector CD4+ T cells, with the innate compartment (neutrophils, macrophages, and monocytes) contributing crucially to tissue degeneration that occurs at later phases of the disease. However, how the immune attack is orchestrated by various immune cell subsets in the retina and how the latter interact with the target tissue under in vivo conditions is still poorly understood. Our study addresses this gap with a novel approach for intravital two-photon microscopy, which enabled us to repeatedly track CD4+ T cells and LysM phagocytes during the entire course of EAU and to identify a specific radial infiltration pattern of these cells within the inflamed retina, starting from the optic nerve head. In contrast, highly motile CX3CR1+ cells display an opposite radial motility pattern, toward the optic nerve head. These inflammatory processes induce modifications of the microglial network toward an activated morphology, especially around the optic nerve head and main retinal blood vessels, but do not affect the neurons within the ganglion cell layer. Thanks to the new technology, non-invasive correlation of clinical scores of CNS-related pathologies with immune infiltrate behavior and subsequent tissue dysfunction is now possible. Hence, the new approach paves the way for deeper insights into the pathology of neuroinflammatory processes on a cellular basis, over the entire disease course.
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Affiliation(s)
- Daniel Bremer
- German Rheumatism Research Center , Berlin , Germany
| | - Florence Pache
- German Rheumatism Research Center, Berlin, Germany; NeuroCure Clinical Research Center, Clinical and Experimental Multiple Sclerosis Research Center, Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | | | | | | | - Ruth Leben
- German Rheumatism Research Center , Berlin , Germany
| | - Ronja Mothes
- German Rheumatism Research Center, Berlin, Germany; Department of Neuropathology, Charité - Universitätsmedizin, Berlin, Germany
| | - Hanna Zimmermann
- NeuroCure Clinical Research Center, Clinical and Experimental Multiple Sclerosis Research Center, Department of Neurology, Charité - Universitätsmedizin Berlin , Berlin , Germany
| | - Alexander U Brandt
- NeuroCure Clinical Research Center, Clinical and Experimental Multiple Sclerosis Research Center, Department of Neurology, Charité - Universitätsmedizin Berlin , Berlin , Germany
| | - Friedemann Paul
- NeuroCure Clinical Research Center, Clinical and Experimental Multiple Sclerosis Research Center, Department of Neurology, Charité - Universitätsmedizin Berlin , Berlin , Germany
| | - Anja E Hauser
- German Rheumatism Research Center, Berlin, Germany; Immundynamics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Helena Radbruch
- Department of Neuropathology, Charité - Universitätsmedizin , Berlin , Germany
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15
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Cua M, Wahl DJ, Zhao Y, Lee S, Bonora S, Zawadzki RJ, Jian Y, Sarunic MV. Coherence-Gated Sensorless Adaptive Optics Multiphoton Retinal Imaging. Sci Rep 2016; 6:32223. [PMID: 27599635 PMCID: PMC5013266 DOI: 10.1038/srep32223] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 08/04/2016] [Indexed: 11/09/2022] Open
Abstract
Multiphoton microscopy enables imaging deep into scattering tissues. The efficient generation of non-linear optical effects is related to both the pulse duration (typically on the order of femtoseconds) and the size of the focused spot. Aberrations introduced by refractive index inhomogeneity in the sample distort the wavefront and enlarge the focal spot, which reduces the multiphoton signal. Traditional approaches to adaptive optics wavefront correction are not effective in thick or multi-layered scattering media. In this report, we present sensorless adaptive optics (SAO) using low-coherence interferometric detection of the excitation light for depth-resolved aberration correction of two-photon excited fluorescence (TPEF) in biological tissue. We demonstrate coherence-gated SAO TPEF using a transmissive multi-actuator adaptive lens for in vivo imaging in a mouse retina. This configuration has significant potential for reducing the laser power required for adaptive optics multiphoton imaging, and for facilitating integration with existing systems.
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Affiliation(s)
- Michelle Cua
- School of Engineering Science, Simon Fraser University, Burnaby, BC V5A 1S6 Canada
| | - Daniel J Wahl
- School of Engineering Science, Simon Fraser University, Burnaby, BC V5A 1S6 Canada
| | - Yuan Zhao
- School of Engineering Science, Simon Fraser University, Burnaby, BC V5A 1S6 Canada
| | - Sujin Lee
- School of Engineering Science, Simon Fraser University, Burnaby, BC V5A 1S6 Canada
| | - Stefano Bonora
- CNR-Institute for Photonics and Nanotechnology, Via Trasea 7, 35131, Padova, Italy
| | - Robert J Zawadzki
- UC Davis RISE Small Animal Ocular Imaging Facility, Department of Cell Biology and Human Anatomy, University of California Davis, Davis, CA 95616, USA.,Vision Science and Advanced Retinal Imaging laboratory (VSRI), Department of Ophthalmology &Vision Science, University of California Davis, Sacramento, CA 95817 USA
| | - Yifan Jian
- School of Engineering Science, Simon Fraser University, Burnaby, BC V5A 1S6 Canada
| | - Marinko V Sarunic
- School of Engineering Science, Simon Fraser University, Burnaby, BC V5A 1S6 Canada
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16
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Alexander NS, Palczewska G, Stremplewski P, Wojtkowski M, Kern TS, Palczewski K. Image registration and averaging of low laser power two-photon fluorescence images of mouse retina. BIOMEDICAL OPTICS EXPRESS 2016; 7:2671-91. [PMID: 27446697 PMCID: PMC4948621 DOI: 10.1364/boe.7.002671] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 06/11/2016] [Accepted: 06/11/2016] [Indexed: 05/18/2023]
Abstract
Two-photon fluorescence microscopy (TPM) is now being used routinely to image live cells for extended periods deep within tissues, including the retina and other structures within the eye . However, very low laser power is a requirement to obtain TPM images of the retina safely. Unfortunately, a reduction in laser power also reduces the signal-to-noise ratio of collected images, making it difficult to visualize structural details. Here, image registration and averaging methods applied to TPM images of the eye in living animals (without the need for auxiliary hardware) demonstrate the structural information obtained with laser power down to 1 mW. Image registration provided between 1.4% and 13.0% improvement in image quality compared to averaging images without registrations when using a high-fluorescence template, and between 0.2% and 12.0% when employing the average of collected images as the template. Also, a diminishing return on image quality when more images were used to obtain the averaged image is shown. This work provides a foundation for obtaining informative TPM images with laser powers of 1 mW, compared to previous levels for imaging mice ranging between 6.3 mW [Palczewska G., Nat Med.20, 785 (2014) Sharma R., Biomed. Opt. Express4, 1285 (2013)].
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Affiliation(s)
- Nathan S Alexander
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA;
| | | | - Patrycjusz Stremplewski
- Faculty of Physics, Astronomy and Informatics, Institute of Physics, Nicolaus Copernicus University, 87-100 Torun, Poland
| | - Maciej Wojtkowski
- Faculty of Physics, Astronomy and Informatics, Institute of Physics, Nicolaus Copernicus University, 87-100 Torun, Poland
| | - Timothy S Kern
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; Polgenix Inc., 11000 Cedar Ave, Cleveland, Ohio 44106, USA;
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17
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Sen D, SoRelle ED, Liba O, Dalal R, Paulus YM, Kim TW, Moshfeghi DM, de la Zerda A. High-resolution contrast-enhanced optical coherence tomography in mice retinae. JOURNAL OF BIOMEDICAL OPTICS 2016; 21:66002. [PMID: 27264492 PMCID: PMC4893203 DOI: 10.1117/1.jbo.21.6.066002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 05/02/2016] [Indexed: 05/14/2023]
Abstract
Optical coherence tomography (OCT) is a noninvasive interferometric imaging modality providing anatomical information at depths of millimeters and a resolution of micrometers. Conventional OCT images limit our knowledge to anatomical structures alone, without any contrast enhancement. Therefore, here we have, for the first time, optimized an OCT-based contrast-enhanced imaging system for imaging single cells and blood vessels in vivo inside the living mouse retina at subnanomolar sensitivity. We used bioconjugated gold nanorods (GNRs) as exogenous OCT contrast agents. Specifically, we used anti-mouse CD45 coated GNRs to label mouse leukocytes and mPEG-coated GNRs to determine sensitivity of GNR detection in vivo inside mice retinae. We corroborated OCT observations with hyperspectral dark-field microscopy of formalin-fixed histological sections. Our results show that mouse leukocytes that otherwise do not produce OCT contrast can be labeled with GNRs leading to significant OCT intensity equivalent to a 0.5 nM GNR solution. Furthermore, GNRs injected intravenously can be detected inside retinal blood vessels at a sensitivity of ∼0.5 nM, and GNR-labeled cells injected intravenously can be detected inside retinal capillaries by enhanced OCT contrast. We envision the unprecedented resolution and sensitivity of functionalized GNRs coupled with OCT to be adopted for longitudinal studies of retinal disorders.
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Affiliation(s)
- Debasish Sen
- Stanford University, Department of Structural Biology, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Molecular Imaging Program at Stanford, 299 Campus Drive, Stanford, California 94305, United States
| | - Elliott D. SoRelle
- Stanford University, Department of Structural Biology, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Biophysics Program, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Department of Electrical Engineering, 299 Campus Drive, Stanford, California 94305, United States
| | - Orly Liba
- Stanford University, Department of Structural Biology, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Molecular Imaging Program at Stanford, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Department of Electrical Engineering, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Bio-X Program, 299 Campus Drive, Stanford, California, 94305, United States
| | - Roopa Dalal
- Stanford University, Department of Ophthalmology, 300 Pasteur Drive, Palo Alto, California 94304, United States
| | - Yannis M. Paulus
- Stanford University, Department of Structural Biology, 299 Campus Drive, Stanford, California 94305, United States
| | - Tae-Wan Kim
- Stanford University, Department of Structural Biology, 299 Campus Drive, Stanford, California 94305, United States
| | - Darius M. Moshfeghi
- Stanford University, Bio-X Program, 299 Campus Drive, Stanford, California, 94305, United States
- Stanford University, Department of Ophthalmology, Stanford Byers Eye Institute, 2452 Watson Court, Palo Alto, California 94303, United States
| | - Adam de la Zerda
- Stanford University, Department of Structural Biology, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Molecular Imaging Program at Stanford, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Biophysics Program, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Department of Electrical Engineering, 299 Campus Drive, Stanford, California 94305, United States
- Stanford University, Bio-X Program, 299 Campus Drive, Stanford, California, 94305, United States
- Address all correspondence to: Adam de la Zerda, E-mail:
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18
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Zhang P, Goswami M, Zam A, Pugh EN, Zawadzki RJ. Effect of scanning beam size on the lateral resolution of mouse retinal imaging with SLO. OPTICS LETTERS 2015; 40:5830-3. [PMID: 26670523 PMCID: PMC4915368 DOI: 10.1364/ol.40.005830] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Scanning laser ophthalmoscopy (SLO) employs the eye's optics as a microscope objective for retinal imaging in vivo. The mouse retina has become an increasingly important object for investigation of ocular disease and physiology with optogenetic probes. SLO imaging of the mouse eye, in principle, can achieve submicron lateral resolution thanks to a numerical aperture (NA) of ∼0.5, about 2.5 times larger than that of the human eye. In the absence of adaptive optics, however, natural ocular aberrations limit the available optical resolution. The use of a contact lens, in principle, can correct many aberrations, permitting the use of a wider scanning beam and, thus, achieving greater resolution then would otherwise be possible. In this Letter, using an SLO equipped with a rigid contact lens, we report the effect of scanning beam size on the lateral resolution of mouse retinal imaging. Theory predicts that the maximum beam size full width at half-maximum (FWHM) that can be used without any deteriorating effects of aberrations is ∼0.6 mm. However, increasing the beam size up to the diameter of the dilated pupil is predicted to improve lateral resolution, though not to the diffraction limit. To test these predictions, the dendrites of a retinal ganglion cell expressing YFP were imaged, and transverse scans were analyzed to quantify the SLO system resolution. The results confirmed that lateral resolution increases with the beam size as predicted. With a 1.3 mm scanning beam and no high-order aberration correction, the lateral resolution is ∼1.15 μm, superior to that achievable by most human AO-SLO systems. Advantages of this approach include stabilization of the mouse eye and simplified optical design.
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Affiliation(s)
- Pengfei Zhang
- UC Davis RISE Eye-Pod Small Animal Imaging Laboratory, Department of Cell Biology and Human Anatomy, University of California Davis, 4320 Tupper Hall, Davis, California 95616, USA
| | - Mayank Goswami
- UC Davis RISE Eye-Pod Small Animal Imaging Laboratory, Department of Cell Biology and Human Anatomy, University of California Davis, 4320 Tupper Hall, Davis, California 95616, USA
| | - Azhar Zam
- UC Davis RISE Eye-Pod Small Animal Imaging Laboratory, Department of Cell Biology and Human Anatomy, University of California Davis, 4320 Tupper Hall, Davis, California 95616, USA
| | - Edward N. Pugh
- UC Davis RISE Eye-Pod Small Animal Imaging Laboratory, Department of Cell Biology and Human Anatomy, University of California Davis, 4320 Tupper Hall, Davis, California 95616, USA
| | - Robert J. Zawadzki
- UC Davis RISE Eye-Pod Small Animal Imaging Laboratory, Department of Cell Biology and Human Anatomy, University of California Davis, 4320 Tupper Hall, Davis, California 95616, USA
- UC Davis Eye Center, Department of Ophthalmology & Vision Science, University of California Davis, 4860 Y Street, Suite 2400, Sacramento, California 95817, USA
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