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Pattanaik DK, Lakshminarayanan V, Sharma NK, Sahu AP. Leading edge of the a-wave of the electroretinogram and sodium iodate-induced age-related macular degeneration: A model. J Theor Biol 2024; 592:111879. [PMID: 38909882 DOI: 10.1016/j.jtbi.2024.111879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 05/12/2024] [Accepted: 06/10/2024] [Indexed: 06/25/2024]
Abstract
BACKGROUND Iron-induced oxidative stress was thought to be the reason why the a-wave amplitude of the electroretinogram (ERG) dropped when iron ions were present. It is assumed that reactive oxygen species (ROS) are generated in the presence of iron ions, and this leads to a decrease in hyperpolarization of the photoreceptor. It is known that in age-related macular degeneration (AMD), sodium iodate can induce oxidative stress, apoptosis, and retinal damage, which mimic the effects of clinical AMD. Here, the reduction of the a-wave amplitude in mice with sodium iodate-induced age-related macular degeneration is explained. METHODS The leading edge of the a-wave is divided into voltages developed by cones and rods. The same oxidative stress model is applied here since sodium iodate causes the creation of ROS in a manner similar to that caused by iron ions, with the exception that the retina is treated as a circuit of various resistances when computing the photoresponse. Moreover, sodium iodate also leads to apoptosis and, hence, may cause misalignment in cones (not in rods) during the initial stage of apoptosis in AMD. To include the effects of apoptosis and shortening in cones and rods, we have used a factor representing the fraction of total cones and rods that are alive. To include the effect of misalignment of cones on the reduction of the a-wave amplitude, we have used the Stiles-Crawford function to calculate the number of photoisomerizations occurring in a photoreceptor misaligned at an angle θ. The results are compared with experimental data. RESULTS In sodium iodate-treated eyes, the ROS produced can attract calcium ions in the photoreceptor, which increases the calcium influx. In the case of the cones, the inclusion of the misalignment angle in the phototransduction process helps in determining the voltage and slope of the voltage vs. time graph.The smaller the fraction of active photoreceptors, the smaller the amplitude of the a-wave. The calcium influx, misaligned photoreceptors, and total photoreceptor loss all cause the amplitude of the a-wave to decrease, and at any time from the beginning of phototransduction cascade, the calcium influx causes the slope of the a-wave to increase. CONCLUSION The reduction in the a-wave amplitude in the eyes of sodium iodate-treated mice is attributed to oxidative stress in both cones and rods and cone misalignment, which ultimately lead to apoptosis and vision loss in AMD.
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Affiliation(s)
| | - Vasudevan Lakshminarayanan
- School of Optometry and Vision Science and Departments of Physics, Electrical and Computer Engineering and System Design Engineering, University of Waterloo, Waterloo, Canada.
| | | | - Amir Prasad Sahu
- Centurion University of Technology and Management, Bhubaneswar, OR, India.
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Bang SP, Lyu J, Ng CJ, Yoon G. Visual Axis and Stiles-Crawford Effect Peak Show a Positional Correlation in Normal Eyes: A Cohort Study. Invest Ophthalmol Vis Sci 2022; 63:26. [PMID: 36306143 PMCID: PMC9624269 DOI: 10.1167/iovs.63.11.26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 10/03/2022] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of this study was to locate the visual axis and evaluate its correlation with the Stiles-Crawford effect (SCE) peak. Methods Ten young, healthy individuals (20 eyes) were enrolled. An optical system was developed to locate the visual axis and measure SCE. To locate the visual axis, 2 small laser spots at 450 nm and 680 nm were co-aligned and delivered to the retina. The participants were asked to move a translatable pinhole until these spots were perceived to overlap each other. The same system assessed SCE at 680 nm using a bipartite, 2-channel (reference and test) Maxwellian-view optical system. The peak positions were estimated using a two-dimensional Gaussian fitting function and correlated with the visual axis positions. Results Both the visual axis (x = 0.24 ± 0.35 mm, y = -0.16 ± 0.34 mm) and the SCE peak (x = 0.27 ± 0.35 mm, y = -0.15 ± 0.31 mm) showed intersubject variability among the cohort. The SCE peak positions were highly correlated in both the horizontal and vertical meridians to the visual axes (R2 = 0.98 and 0.96 for the x and y coordinates, respectively). Nine of the 10 participants demonstrated mirror symmetry for the coordinates of the visual axis and the SCE peak between the eyes (R2 = 0.71 for the visual axis and 0.76 for the SCE peak). Conclusions The visual axis and SCE peak locations varied among the participants; however, they were highly correlated with each other for each individual. These findings suggest a potential mechanism underlying the foveal cone photoreceptor alignment.
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Affiliation(s)
- Seung Pil Bang
- Department of Biomedical Engineering, University of Rochester, Rochester, New York, USA
| | - Jiakai Lyu
- Institute of Optics, University of Rochester, Rochester, New York, USA
| | - Cherlyn J. Ng
- College of Optometry, University of Houston, Houston, Texas, USA
| | - Geunyoung Yoon
- College of Optometry, University of Houston, Houston, Texas, USA
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NoroozOliaei M, Riazi Esfahani H, Abrishamian MS. Graphene coated dielectric resonator antenna for modeling the photoreceptors at visible spectrum. Heliyon 2022; 8:e09611. [PMID: 35928439 PMCID: PMC9344327 DOI: 10.1016/j.heliyon.2022.e09611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/16/2022] [Accepted: 05/27/2022] [Indexed: 11/19/2022] Open
Abstract
The absorption of light is very important task for retina photoreceptors. Graphene is an energy harvesting material and one of the best models for the electromagnetic wave absorption and its conversion into signals. In this paper, an electromagnetic modeling of human retinal photoreceptors has been presented based on graphene coated material as a receiver antenna. The proposed electromagnetic model based on dielectric resonator antenna (DRA) is being analyzed for retina photoreceptors of human eye (cones and rods) by Finite Integral Method (FIM) collaborated with CST MWS. The results show that the model is good for vision spectrum with a proper field enhancement in cone photoreceptor due to its sensitivity to light. The results indicate proper S11 (return loss below −10 dB) with invaluable resonances in a wide range of frequencies from 405 THz to 790 THz (vision spectrum), suitable S21 (insertion loss 3-dB bandwidth), very good field distribution for flowing the power within desired radiation characteristics. The drawbacks of conventional model (no coating) have been resolved by presenting this one at blue spectrum specifically. Finally, mfERG clinical and experimental results show that this model can stimulate the electrochemical voltages and currents in photoreceptor cells.
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Affiliation(s)
- Mahdi NoroozOliaei
- Electrical & Computer Engineering Department, K. N. Toosi University of Technology, Tehran, Iran
- Corresponding author.
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Vohnsen B. Geometrical scaling of the developing eye and photoreceptors and a possible relation to emmetropization and myopia. Vision Res 2021; 189:46-53. [PMID: 34619411 DOI: 10.1016/j.visres.2021.09.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/10/2021] [Accepted: 09/22/2021] [Indexed: 10/20/2022]
Abstract
In this study the role of vergence in relation to age-dependent scaling of eye and photoreceptor parameters is studied. The underlying hypothesis is that the size and packing of outer segments is matched to the pupil size outdoors in photopic conditions. Vergence is analysed in relation to the angular spectrum of waves being incident using age-dependent data from the literature for the actual geometry and density of photoreceptor cones and rods. This approach is used to derive simple relations for the angular confinement of light along outer segments. Only with a small photopic pupil can leakage and crosstalk for both central and peripheral photoreceptors be entirely ruled out due to the finite length of the outer segments. A limiting 3 mm pupil size is found for children in the school age. Larger pupils will increase the likelihood of leakage and crosstalk that may therefore impact on emmetropization. This study has introduced a new paradigm in myopia research by considering vergence across the 3-D retina as being matched to the angular spectrum of waves being incident from the eye pupil. Emmetropization suggests a delicate balance between photoreceptor outer segment length and density in relation to pupil size. Only when balanced will leakage and crosstalk between adjacent outer segments be effectively suppressed thereby ensuring the highest possible light capture efficiency by visual pigments in the outer segments whether an image is formed on the retina or not.
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Affiliation(s)
- Brian Vohnsen
- Advanced Optical Imaging Group, School of Physics, University College Dublin, Ireland.
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Gaffney M, Cooper RF, Cava JA, Follett HM, Salmon AE, Freling S, Yu CT, Merriman DK, Carroll J. Cone photoreceptor reflectance variation in the northern tree shrew and thirteen-lined ground squirrel. Exp Biol Med (Maywood) 2021; 246:2192-2201. [PMID: 34308656 PMCID: PMC8718250 DOI: 10.1177/15353702211029582] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 06/14/2021] [Indexed: 12/30/2022] Open
Abstract
In vivo images of human cone photoreceptors have been shown to vary in their reflectance both spatially and temporally. While it is generally accepted that the unique anatomy and physiology of the photoreceptors themselves drives this behavior, the exact mechanisms have not been fully elucidated as most studies on these phenomena have been limited to the human retina. Unlike humans, animal models offer the ability to experimentally manipulate the retina and perform direct in vivo and ex vivo comparisons. The thirteen-lined ground squirrel and northern tree shrew are two emerging animal models being used in vision research. Both models feature cone-dominant retinas, overcoming a key limitation of traditional rodent models. Additionally, each possesses unique but well-documented anatomical differences in cone structure compared to human cones, which can be leveraged to further constrain theoretical models of light propagation within photoreceptors. Here we sought to characterize the spatial and temporal reflectance behavior of cones in these species. Adaptive optics scanning light ophthalmoscopy (AOSLO) was used to non-invasively image the photoreceptors of both species at 5 to 10 min intervals over the span of 18 to 25 min. The reflectance of individual cone photoreceptors was measured over time, and images at individual time points were used to assess the variability of cone reflectance across the cone mosaic. Variability in spatial and temporal photoreceptor reflectance was observed in both species, with similar behavior to that seen in human AOSLO images. Despite the unique cone structure in these animals, these data suggest a common origin of photoreceptor reflectance behavior across species. Such data may help constrain models of the cellular origins of photoreceptor reflectance signals. These animal models provide an experimental platform to further explore the morphological origins of light capture and propagation.
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Affiliation(s)
- Mina Gaffney
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Robert F Cooper
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Biomedical Engineering, Marquette University, Milwaukee, WI 53233, USA
| | - Jenna A Cava
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Hannah M Follett
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Alexander E Salmon
- Department of Cell Biology, Neurobiology, & Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Translational Imaging Innovations, Inc., Hickory, NC 28601, USA
| | - Susan Freling
- Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Ching T Yu
- Department of Cell Biology, Neurobiology, & Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Dana K Merriman
- Department of Biology, University of Wisconsin Oshkosh, Oshkosh, WI 54901, USA
| | - Joseph Carroll
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
- Department of Biomedical Engineering, Marquette University, Milwaukee, WI 53233, USA
- Department of Cell Biology, Neurobiology, & Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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Valente D, Vienola KV, Zawadzki RJ, Jonnal RS. Simultaneous directional full-field OCT using path-length and carrier multiplexing. OPTICS EXPRESS 2021; 29:32179-32195. [PMID: 34615295 PMCID: PMC8687100 DOI: 10.1364/oe.435761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 09/02/2021] [Accepted: 09/07/2021] [Indexed: 06/13/2023]
Abstract
Full-field swept-source optical coherence tomography (FF-SS-OCT) is an emerging technology with potential applications in ophthalmic imaging, microscopy, metrology, and other domains. Here we demonstrate a novel method of multiplexing FF-SS-OCT signals using carrier modulation (CM). The principle of CM could be used to inspect various properties of the scattered light, e.g. its spectrum, polarization, Doppler shift, or distribution in the pupil. The last of these will be explored in this work, where CM was used to acquire images passing through two different optical pupils. The two pupils contained semicircular optical windows with perpendicular orientations, with each window permitting measurement of scattering anisotropy in one dimension by inducing an optical delay between the images formed by the two halves of the pupil. Together, the two forms of multiplexing permit measurement of differential scattering anisotropy in the x and y dimensions simultaneously. To demonstrate the feasibility of this technique our carrier multiplexed directional FF-OCT (CM-D-FF-OCT) system was used to acquire images of a microlens array, human hair, onion skin and in vivo human retina. The results of these studies are presented and briefly discussed in the context of future development and application of this technique.
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Affiliation(s)
- Denise Valente
- Vision Science and Advanced Retinal Imaging Laboratory (VSRI), Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, CA 95817, USA
| | - Kari V. Vienola
- Vision Science and Advanced Retinal Imaging Laboratory (VSRI), Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, CA 95817, USA
| | - Robert J. Zawadzki
- Vision Science and Advanced Retinal Imaging Laboratory (VSRI), Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, CA 95817, USA
- EyePod Small Animal Ocular Imaging Laboratory, Department of Cell Biology and Human Anatomy, University of California Davis, Davis, CA 95616, USA
| | - Ravi S. Jonnal
- Vision Science and Advanced Retinal Imaging Laboratory (VSRI), Department of Ophthalmology and Vision Science, University of California Davis, Sacramento, CA 95817, USA
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Nilagiri VK, Suheimat M, Lambert AJ, Atchison DA. Subjective measurement of the Stiles-Crawford effect of the first kind with variation in accommodation. Ophthalmic Physiol Opt 2021; 41:1110-1118. [PMID: 34387885 DOI: 10.1111/opo.12855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 05/31/2021] [Accepted: 06/01/2021] [Indexed: 11/28/2022]
Abstract
PURPOSE To measure the Stiles-Crawford effect of the first kind (SCE-I), corresponding to central vision, with innovative technology to evaluate changes in the directionality and photoreceptor alignment with accommodation. METHODS A uniaxial Maxwellian system (spot size in pupil 0.5 mm diameter) was employed, incorporating a spatial light modulator to flicker at 2 Hz between two 2.3° fields corresponding to test (peripheral pupil) and reference (pupil centre) positions. Participants determined thresholds at 13 positions along the horizontal pupil meridian by indicating if the test field was brighter or dimmer than the reference field. Thresholds were determined by a staircase procedure after four reversals at each pupil location. After pupil dilation, seven emmetropes were tested at 0 D to 6 D accommodation stimulus levels in 2 D intervals. Data were fit by the Gaussian function, both when the fits were unforced or forced to pass through the sensitivity expected for the reference point. Directionality (ρ) and peak location values ( x max ) were determined for unforced and forced fits. RESULTS Regression slopes for ρ as a function of accommodation stimulus were not significant. There was a tendency for x max to shift temporally with increasing accommodation across the 6 D stimulus range. This was not significant for regression fitting (-0.059 mm/D, R2 = 0.06, p = 0.20), but a paired t-test for 0 and 6 D stimuli showed a weakly significant change of 0.62 mm (p = 0.05). The differences between the two fitting approaches were small and non-significant. CONCLUSIONS Directionality did not change with accommodation, but the pupil peak location showed a significant temporal shift of approximately 0.62 mm with 6 D accommodation stimulus. It is possible that substantial changes in the directionality and a shift in the direction of peak location might occur at very high levels of accommodation.
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Affiliation(s)
- Vinay Kumar Nilagiri
- Centre for Vision and Eye Research, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Marwan Suheimat
- Centre for Vision and Eye Research, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Andrew J Lambert
- School of Engineering and Information Technology, The University of New South Wales, Canberra, Australian Capital Territory, Australia
| | - David A Atchison
- Centre for Vision and Eye Research, Queensland University of Technology, Brisbane, Queensland, Australia
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8
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Nilagiri VK, Suheimat M, Lambert AJ, Turpin A, Vohnsen B, Atchison DA. Subjective measurement of the Stiles-Crawford effect with different field sizes. BIOMEDICAL OPTICS EXPRESS 2021; 12:4969-4981. [PMID: 34513236 PMCID: PMC8407820 DOI: 10.1364/boe.427834] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 07/07/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
The Stiles-Crawford effect of the first kind (SCE) is the phenomenon in which light entering the eye near the center of the pupil appears brighter than light entering near the edge. Previous investigations have found an increase in the directionality (steepness) of the effect as the testing location moves from the center of the visual field to parafoveal positions, but the effect of central field size has not been considered. The influence of field size on the SCE was investigated using a uniaxial Maxwellian system in which stimulus presentation was controlled by an active-matrix liquid crystal display. SCE directionality increased as field size increased from 0.5° to 4.7° diameter, although this was noted in four mild myopes and not in two emmetropes. The change with field size was supported by a geometric optics absorption model.
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Affiliation(s)
- Vinay Kumar Nilagiri
- Institute of Health and Biomedical Innovation, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
| | - Marwan Suheimat
- Institute of Health and Biomedical Innovation, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
| | - Andrew J. Lambert
- School of Engineering and Information Technology, The University of New South Wales, Canberra, ACT, Australia
| | - Andrew Turpin
- School of Computing and Information Systems, The University of Melbourne, Melbourne, VIC, Australia
| | - Brian Vohnsen
- Advanced Optical Imaging Group, School of Physics, University College Dublin, Dublin 4, Ireland
| | - David A. Atchison
- Institute of Health and Biomedical Innovation, School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
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Sredar N, Razeen M, Kowalski B, Carroll J, Dubra A. Comparison of confocal and non-confocal split-detection cone photoreceptor imaging. BIOMEDICAL OPTICS EXPRESS 2021; 12:737-755. [PMID: 33680539 PMCID: PMC7901313 DOI: 10.1364/boe.403907] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 12/18/2020] [Accepted: 12/19/2020] [Indexed: 05/06/2023]
Abstract
Quadrant reflectance confocal and non-confocal scanning light ophthalmoscope images of the photoreceptor mosaic were recorded in a subject with congenital achromatopsia (ACHM) and a normal control. These images, captured with various circular and annular apertures, were used to calculate split-detection images, revealing two cone photoreceptor contrast mechanisms. The first contrast mechanism, maximal in the non-confocal 5.5-10 Airy disk diameter annular region, is unrelated to the cone reflectivity in confocal or flood illumination imaging. The second mechanism, maximal for confocal split-detection, is related to the cone reflectivity in confocal or flood illumination imaging that originates from the ellipsoid zone and/or inner-outer segment junction. Seeking to maximize image contrast, split-detection images were generated using various quadrant detector combinations, with opposite (diagonal) quadrant detectors producing the highest contrast. Split-detection generated with the addition of adjacent quadrant detector pairs, shows lower contrast, while azimuthal split-detection images, calculated from adjacent quadrant detectors, showed the lowest contrast. Finally, the integration of image pairs with orthogonal split directions was used to produce images in which the photoreceptor contrast does not change with direction.
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Affiliation(s)
- Nripun Sredar
- Department of Ophthalmology, Stanford University, Palo Alto, CA 94303, USA
| | - Moataz Razeen
- Department of Ophthalmology, Stanford University, Palo Alto, CA 94303, USA
| | | | - Joseph Carroll
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Alfredo Dubra
- Department of Ophthalmology, Stanford University, Palo Alto, CA 94303, USA
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Kumar A, Yaduvanshi RS. Quantum antenna operating at 430 to 750 THz band, inspired through human eye. JOURNAL OF INFORMATION & OPTIMIZATION SCIENCES 2020. [DOI: 10.1080/02522667.2020.1809093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Ashok Kumar
- University School of Information, Communication & Technology, Guru Gobind Singh Inderprastha University, Sector 16 C, Dwarka, New Delhi 110078, India
| | - Rajveer S. Yaduvanshi
- Department of Electronics & Communication Engineering, Ambedkar Institute of Advanced Communication Technologies & Research Geeta Colony, New Delhi 110031, India
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Subtype-differentiated impacts of subretinal drusenoid deposits on photoreceptors revealed by adaptive optics scanning laser ophthalmoscopy. Graefes Arch Clin Exp Ophthalmol 2020; 258:1931-1940. [PMID: 32488329 DOI: 10.1007/s00417-020-04774-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 05/17/2020] [Accepted: 05/26/2020] [Indexed: 02/02/2023] Open
Abstract
PURPOSE To examine the structure of photoreceptors surrounding two subtypes of subretinal drusenoid deposits (SDD), namely, dot and ribbon SDD, using multimodal imaging including adaptive optics scanning laser ophthalmoscopy (AOSLO) and spectral-domain optical coherence tomography (SD-OCT). METHODS Twenty-six eyes of 13 patients with age-related macular degeneration (AMD) and SDD and 16 eyes of 8 subjects in normal chorioretinal health were studied. SDD presence, stage, and subtype were determined using color fundus photographs, infrared reflectance, autofluorescence imaging, and SD-OCT. SDD and surrounding photoreceptors were imaged using AOSLO. The structure of cone photoreceptors and SDD was examined at the baseline and at 2-year follow-up studies in 6 patients. RESULTS Dot SDD were identified in 18 eyes of 9 patients and coexisting dot and ribbon SDD were observed in 8 eyes of 4 patients. While a characteristic photoreceptor mosaic was clearly revealed by AOSLO in the area unaffected by lesions in those eyes with dot-only SDD, in unaffected areas adjacent to retinal regions with predominantly ribbon SDD, photoreceptors could no longer be visualized. CONCLUSION The invisibility of the photoreceptor mosaic in unaffected areas adjacent to retinal regions with predominantly ribbon SDD suggests degeneration in the outer segment and the interdigitation zone, which impairs the waveguiding ability of the photoreceptors. Our study implies possible differentiation of disease outcome and functional impact in different types of SDD.
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Menghini M, Cehajic-Kapetanovic J, MacLaren RE. Monitoring progression of retinitis pigmentosa: current recommendations and recent advances. Expert Opin Orphan Drugs 2020; 8:67-78. [PMID: 32231889 PMCID: PMC7104334 DOI: 10.1080/21678707.2020.1735352] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 02/24/2020] [Indexed: 10/24/2022]
Abstract
INTRODUCTION Retinitis pigmentosa (RP) is the most common form of inherited retinal degenerations with an estimated prevalence of 1 in 4,000 and more than 1 million individuals affected worldwide. With the introduction of the first retinal gene therapy in 2017 the importance of understanding the mechanisms of retinal degeneration and its natural progression has shifted from being of academic interest to being of pivotal for the development of new therapies. AREAS COVERED This review covers standard and innovative diagnostic techniques and complementary examinations needed for the evaluation and treatment of RP. It includes chapters on the assessment of visual function, retinal morphology, and genotyping. EXPERT OPINION Monitoring the progression of RP can best be achieved by combining assessments of both visual function and morphology. Visual acuity testing using ETDRS charts should be complemented by low-luminance visual acuity and colour vision tests. Assessment of the visual field can also be useful in less advanced cases. In those with central RP involvement measuring retinal sensitivity using microperimetry is recommended. Retinal morphology is best assessed by OCT and autofluorescence. Genetic testing is pivotal as it contributes to the pathophysiological understanding and can guide clinical management as well as identify individuals that could benefit from retinal gene therapy.
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Affiliation(s)
- Moreno Menghini
- Oxford Eye Hospital and Nuffield Department of Clinical Neurosciences, Oxford University, The John Radcliffe Hospital, West Wing, Oxford OX3 9DU, United Kingdom, +41 79 704 52 58
| | - Jasmina Cehajic-Kapetanovic
- Oxford Eye Hospital and Nuffield Department of Clinical Neurosciences, Oxford University, The John Radcliffe Hospital, West Wing, Oxford OX3 9DU, United Kingdom, +44 7725 197054
| | - Robert E MacLaren
- Oxford Eye Hospital and Nuffield Department of Clinical Neurosciences, Oxford University, The John Radcliffe Hospital, West Wing, Oxford OX3 9DU, United Kingdom, +44 1865 228974
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Meadway A, Sincich LC. Light reflectivity and interference in cone photoreceptors. BIOMEDICAL OPTICS EXPRESS 2019; 10:6531-6554. [PMID: 31853415 PMCID: PMC6913404 DOI: 10.1364/boe.10.006531] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 10/31/2019] [Accepted: 11/03/2019] [Indexed: 05/04/2023]
Abstract
In several modes of retinal imaging, the primary means of visualizing cone photoreceptors is from reflected light. Understanding how such images are formed, particularly when adaptive optics techniques are used, will help to guide their interpretation. Toward this end, we used finite difference beam propagation to model reflections from cone photoreceptors. We investigated the formation of cone images in adaptive optics scanning laser ophthalmoscopy (AOSLO) and optical coherence tomography (AOOCT). Three cone models were tested, one made up of three segments of varying refractive index, the other two having additional boundaries at the inner/outer segment junction and outer segment tip. Images formed by the first model did not correspond to AOOCT observations in the literature, while the latter two did. The predicted distributions of reflected light intensity from the latter cone models were compared to the distribution from AOSLO images, both studied with light sources of varied coherence length. The cone model with the most reflections at the inner/outer segment junction best fit the data measured in vivo. These results show that variance in cone reflection can originate from light interfering from reflectors much more closely spaced than the outer segment length. We also show that subtracting images taken with different coherence length sources highlights these changes in interference. Differential coherence images of cones occasionally revealed an annular reflection profile, which modeling showed to be very sensitive to cone size and the gaps bracketing the outer segment, suggesting that such imaging may be useful for probing photoreceptor morphology.
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Affiliation(s)
- Alexander Meadway
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Lawrence C. Sincich
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Monocular accommodation response to random defocus changes induced by a tuneable lens. Vision Res 2019; 165:45-53. [PMID: 31634733 DOI: 10.1016/j.visres.2019.10.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 09/20/2019] [Accepted: 10/01/2019] [Indexed: 11/23/2022]
Abstract
Accommodation of the human eye relies on multiple factors and visual cues that include object size, monochromatic and chromatic aberrations, and vergence. Yet, even in monocular conditions, accommodation corrects for defocus. Studies of eye growth in chicks have addressed whether the retina can decode the sign of defocus as this may play a role for emmetropization and possibly also accommodation. However, findings have not been unambiguous and questions remain. Here, we report on monocular accommodation studies of emmetropic and myopic human subjects to clarify whether foveal vision drives accommodation in the correct direction by removing out-of-focus blur potentially before relying on other cues. Subjects viewed monocularly a green target at 1-meter distance while being presented with a random sequence of negative defocus step changes induced by a pupil-conjugated current-driven tuneable lens. The natural pupil was constricted by a pupil-conjugated motorized iris using three different diameters and target brightness was set with a liquid crystal variable attenuator. A Hartmann-Shack wavefront sensor with an infrared beacon captured real-time changes of defocus and Zernike polynomial coefficients up to 4th radial order. We find that the young adult eye accommodates reliably in the correct direction but with a latency of 300-700 ms. The findings are discussed in relation to an absorption model of light in outer segments that breaks the defocus symmetry and thus may serve as a plausible guide for accommodation and emmetropization.
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15
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Martins AC, Vohnsen B. Directional light-capture efficiency of the foveal and parafoveal photoreceptors at different luminance levels: an experimental and analytical study. BIOMEDICAL OPTICS EXPRESS 2019; 10:3760-3772. [PMID: 31452973 PMCID: PMC6701552 DOI: 10.1364/boe.10.003760] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 06/24/2019] [Accepted: 06/25/2019] [Indexed: 06/10/2023]
Abstract
A gradual drop in visibility with obliquely incident light on retinal photoreceptors is namely described by the Stiles-Crawford effect of the first kind and characterized by a directionality parameter. Using a digital micromirror device in a uniaxial flicker system, here we report on variations of this effect with luminance levels, wavelengths within the visible and near-infrared spectrum and retinal regions ranging from the fovea to 7.5° parafoveal. Results show a consistent directionality in mesopic and photopic conditions. Higher directionality is measured for longer wavelengths, and a decrease with retinal eccentricity is observed. Results are discussed in relation to an absorption model for the visual pigments taking the outer-segment packing and thickness of the neural retina into account. Good correspondence is found without enforcing photoreceptor waveguiding.
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16
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Del Águila-Carrasco AJ, Kruger PB, Lara F, López-Gil N. Aberrations and accommodation. Clin Exp Optom 2019; 103:95-103. [PMID: 31284325 DOI: 10.1111/cxo.12938] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 12/26/2022] Open
Abstract
Modern methods of measuring the refractive state of the eye include wavefront sensors which make it possible to monitor both static and dynamic changes of the ocular wavefront while the eye observes a target positioned at different distances away from the eye. In addition to monitoring the ocular aberrations, wavefront refraction methods allow measurement of the accommodative response while viewing with the eye's habitual chromatic and monochromatic aberrations present, with these aberrations removed, and with specific aberrations added or removed. A large number of experiments describing the effects of accommodation on aberrations and vice versa are reviewed, pointing out the implications for fundamental questions related to the mechanism of accommodation.
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Affiliation(s)
| | - Philip B Kruger
- College of Optometry, The State University of New York, New York, NY, USA
| | - Francisco Lara
- Vision Science Research Group (CiViUM), Instituto Universitario de Investigación en Envejecimiento (IUIE), University of Murcia, Murcia, Spain
| | - Norberto López-Gil
- Vision Science Research Group (CiViUM), Instituto Universitario de Investigación en Envejecimiento (IUIE), University of Murcia, Murcia, Spain
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17
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García-Guerra CE, Martínez-Roda JA, Aldaba M, Díaz-Doutón F, Vilaseca M, Vohnsen B, Pujol J. Method to reduce undesired multiple fundus scattering effects in double-pass systems. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2019; 36:918-924. [PMID: 31045021 DOI: 10.1364/josaa.36.000918] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 03/26/2019] [Indexed: 06/09/2023]
Abstract
Double-pass systems rely on backscattering of light by the human ocular fundus to assess the optical quality of the eye. In this work, we present a method to reduce double-pass image degradation caused by undesired multiple scattering effects in the eye fundus. The reduction is based on combined data processing of simultaneous measurements using two different configurations: one symmetric with equal entrance and exit pupils and another asymmetric with unequal entrance and exit pupils. Under certain conditions, such scattering effects may be effectively suppressed. Measurements of human eyes show that, although multiple fundus scattering imposes a shift on the estimations, double-pass systems can be used to predict the optical quality of the eye within a population.
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Kedia N, Liu Z, Sochol RD, Tam J, Hammer DX, Agrawal A. 3-D printed photoreceptor phantoms for evaluating lateral resolution of adaptive optics imaging systems. OPTICS LETTERS 2019; 44:1825-1828. [PMID: 30933157 DOI: 10.1364/ol.44.001825] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 03/10/2019] [Indexed: 06/09/2023]
Abstract
With adaptive optics (AO), optical coherence tomography and scanning laser ophthalmoscopy imaging systems can resolve individual photoreceptor cells in living eyes, due to enhanced lateral spatial resolution. However, no standard test method exists for experimentally quantifying this parameter in ophthalmic AO imagers. Here, we present three-dimensional (3-D) printed phantoms, which enable the measurement of lateral resolution in an anatomically relevant manner. We used two-photon polymerization to fabricate two phantoms, which mimic the mosaic of cone photoreceptor outer segments at multiple retinal eccentricities. With these phantoms, we demonstrated that the resolution of two multimodal AO systems is similar to theoretical predictions, with some intriguing speckle effects.
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19
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Kirschfeld K. Do Müller Cells Act as Optical Fibers in the Primate Retina? ACTA ACUST UNITED AC 2019; 60:345-348. [DOI: 10.1167/iovs.18-25831] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Kuno Kirschfeld
- Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany
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20
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Qaysi S, Valente D, Vohnsen B. Differential detection of retinal directionality. BIOMEDICAL OPTICS EXPRESS 2018; 9:6318-6330. [PMID: 31065431 PMCID: PMC6490981 DOI: 10.1364/boe.9.006318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 11/11/2018] [Accepted: 11/12/2018] [Indexed: 05/06/2023]
Abstract
An adaptive optics fundus camera has been developed that uses simultaneous capture of multiple images via adjacent pupil sectors to provide directional sensitivity. In the chosen realization, a shallow refractive pyramid prism is used to subdivide backscattered light from the retina into four solid angles. Parafoveal fundus images have been captured for the eyes of three healthy subjects and directional scattering has been determined using horizontal and vertical differentials. The results for the photoreceptor cones, blood vessels, and the optic disc are discussed. In the case of cones, the observations are compared with numerical simulations based on a simplistic light-scattering model. Ultimately, the method may have diagnostic potential for diseases that perturb the microscopic structure of the retina.
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Affiliation(s)
- Salihah Qaysi
- Advanced Optical Imaging Group, School of Physics, University College Dublin, Dublin 4, Ireland
| | - Denise Valente
- Vision Science and Advanced Retinal Imaging Laboratory, University of California-Davis, Sacramento, CA, USA
| | - Brian Vohnsen
- Advanced Optical Imaging Group, School of Physics, University College Dublin, Dublin 4, Ireland
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21
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Meadway A, Sincich LC. Light propagation and capture in cone photoreceptors. BIOMEDICAL OPTICS EXPRESS 2018; 9:5543-5565. [PMID: 30460146 PMCID: PMC6238909 DOI: 10.1364/boe.9.005543] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/21/2018] [Accepted: 10/08/2018] [Indexed: 05/21/2023]
Abstract
The light capturing properties of cone photoreceptors create the elementary signals that form the basis of vision. Variation in the amplitude of individual cone signals has been found physiologically as part of normal retinal circuit processing. Less well characterized is how cone signals may vary due to purely optical properties. We present a model of light propagation in cones using a finite difference beam propagation method to simulate how light from a small stimulus travels through a cone plus its immediate neighbors. The model calculates the amount of light absorbed in the cone outer segments, from which an estimate of the photoresponse can be made. We apply the method to adaptive optics microstimulation to find the optimum optical conditions that will confine the most light into a single cone in the human retina. We found that light capture is especially sensitive to beam size at the pupil and to the cone diameter itself, with the two factors having a complex relationship leading to sizable variation in light capture. Model predictions were validated with two types of psychophysical data. The model can be employed with arbitrary stimuli and photoreceptor parameters, making it a useful tool for studying photoreceptor function in normal or diseased conditions.
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Affiliation(s)
- Alexander Meadway
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Lawrence C. Sincich
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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22
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Song W, Zhou L, Zhang S, Ness S, Desai M, Yi J. Fiber-based visible and near infrared optical coherence tomography (vnOCT) enables quantitative elastic light scattering spectroscopy in human retina. BIOMEDICAL OPTICS EXPRESS 2018; 9:3464-3480. [PMID: 29984110 PMCID: PMC6033571 DOI: 10.1364/boe.9.003464] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/09/2018] [Accepted: 06/21/2018] [Indexed: 05/18/2023]
Abstract
Elastic light scattering spectroscopy (ELSS) has been proven a powerful method in measuring tissue structures with exquisite nanoscale sensitivity. However, ELSS contrast in the living human retina has been relatively underexplored, primarily due to the lack of imaging tools with a large spectral bandwidth. Here, we report a simple all fiber-based setup to implement dual-channel visible and near infrared (NIR) optical coherence tomography (vnOCT) for human retinal imaging, bridging over a 300nm spectral gap. Remarkably, the fiber components in our vnOCT system support single-mode propagation for both visible and NIR light, both of which maintain excellent interference efficiencies with fringe visibility of 97% and 90%, respectively. The longitudinal chromatic aberration from the eye is corrected by a custom-designed achromatizing lens. The elegant fiber-based design enables simultaneous imaging for both channels and allows comprehensive ELSS analysis on several important anatomical layers, including nerve fiber layer, outer segment of the photoreceptors and retinal pigment epithelium. This vnOCT platform and method of ELSS analysis open new opportunities in understanding structure-function relationship in the human retina and in exploring new biomarkers for retinal diseases.
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Affiliation(s)
- Weiye Song
- Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, MA 02118, USA
| | - Libo Zhou
- College of Electronic Science and Engineering, Jilin University, Changchun, Jilin, 130012, China
| | - Sui Zhang
- Danna-Farber Cancer Institute, Boston, MA 02215, USA
| | - Steven Ness
- Department of Ophthalmology, Boston Medical Center, Boston University School of Medicine, Boston, MA 02118, USA
| | - Manishi Desai
- Department of Ophthalmology, Boston Medical Center, Boston University School of Medicine, Boston, MA 02118, USA
| | - Ji Yi
- Department of Medicine, Boston University School of Medicine, Boston Medical Center, Boston, MA 02118, USA
- Department of Biomedical Engineering, Boston University, Boston, MA 02118, USA
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23
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Valente D, Vohnsen B. Retina-simulating phantom produced by photolithography. OPTICS LETTERS 2017; 42:4623-4626. [PMID: 29140328 DOI: 10.1364/ol.42.004623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 10/10/2017] [Indexed: 05/22/2023]
Abstract
Cone photoreceptors have a narrow acceptance angle that is well matched to the size of the eye pupil and dampens the visual impact of aberrations and scattering. However, the structure of the human retina is not replicated in existing eye models used to test refractive designs or retinal implants that restore partial vision to the blind. Here, we report on an artificial waveguide-based retinal phantom manufactured by photolithography in photoresist film with dimensions and refractive index contrast similar to the retinal receptor layer. The optical performance of the waveguide array is analyzed in terms of angular coupling efficiency, and it is experimentally verified that the structure leads to improved resolution and contrast of optical images transmitted through the layer when defocus is present.
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24
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Marín-Franch I, Del Águila-Carrasco AJ, Bernal-Molina P, Esteve-Taboada JJ, López-Gil N, Montés-Micó R, Kruger PB. There is more to accommodation of the eye than simply minimizing retinal blur. BIOMEDICAL OPTICS EXPRESS 2017; 8:4717-4728. [PMID: 29082097 PMCID: PMC5654812 DOI: 10.1364/boe.8.004717] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 09/02/2017] [Indexed: 06/07/2023]
Abstract
Eyes of children and young adults change their optical power to focus nearby objects at the retina. But does accommodation function by trial and error to minimize blur and maximize contrast as is generally accepted? Three experiments in monocular and monochromatic vision were performed under two conditions while aberrations were being corrected. In the first condition, feedback was available to the eye from both optical vergence and optical blur. In the second, feedback was only available from target blur. Accommodation was less precise for the second condition, suggesting that it is more than a trial-and-error function. Optical vergence itself seems to be an important cue for accommodation.
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Affiliation(s)
- I. Marín-Franch
- Department of Optics and Optometry and Vision Sciences, University of Valencia, Spain
- Interuniversity Laboratory for Research in Vision and Optometry, Mixed Group UVEG-UMU, Valencia-Murcia, Spain
- Department of Ophthalmology, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, USA
| | - A. J. Del Águila-Carrasco
- Department of Optics and Optometry and Vision Sciences, University of Valencia, Spain
- Interuniversity Laboratory for Research in Vision and Optometry, Mixed Group UVEG-UMU, Valencia-Murcia, Spain
| | - P. Bernal-Molina
- Department of Optics and Optometry and Vision Sciences, University of Valencia, Spain
- Interuniversity Laboratory for Research in Vision and Optometry, Mixed Group UVEG-UMU, Valencia-Murcia, Spain
| | - J. J. Esteve-Taboada
- Department of Optics and Optometry and Vision Sciences, University of Valencia, Spain
- Interuniversity Laboratory for Research in Vision and Optometry, Mixed Group UVEG-UMU, Valencia-Murcia, Spain
| | - N. López-Gil
- Interuniversity Laboratory for Research in Vision and Optometry, Mixed Group UVEG-UMU, Valencia-Murcia, Spain
- Science Vision Group (CiViUM), Instituto Universitario de Investigación en Envejecimiento, University of Murcia, Spain
| | - R. Montés-Micó
- Department of Optics and Optometry and Vision Sciences, University of Valencia, Spain
- Interuniversity Laboratory for Research in Vision and Optometry, Mixed Group UVEG-UMU, Valencia-Murcia, Spain
| | - P. B. Kruger
- State College of Optometry, State University of New York, New York, USA
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25
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Badhani A, Behera UC. Regeneration of Photoreceptor Outer Segments After Scleral Buckling Surgery for Rhegmatogenous Retinal Detachment. Am J Ophthalmol 2017; 180:178. [PMID: 28577755 DOI: 10.1016/j.ajo.2017.05.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2017] [Revised: 04/26/2017] [Accepted: 05/01/2017] [Indexed: 10/19/2022]
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26
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Bernal-Molina P, Marín-Franch I, Del Águila-Carrasco AJ, Esteve-Taboada JJ, López-Gil N, Kruger PB, Montés-Micó R. Human eyes do not need monochromatic aberrations for dynamic accommodation. Ophthalmic Physiol Opt 2017; 37:602-609. [PMID: 28681436 PMCID: PMC5600112 DOI: 10.1111/opo.12398] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 05/26/2017] [Indexed: 12/28/2022]
Abstract
Purpose To determine if human accommodation uses the eye's own monochromatic aberrations to track dynamic accommodative stimuli. Methods Wavefront aberrations were measured while subjects monocularly viewed a monochromatic Maltese cross moving sinusoidally around 2D of accommodative demand with 1D amplitude at 0.2 Hz. The amplitude and phase (delay) of the accommodation response were compared to the actual vergence of the stimulus to obtain gain and temporal phase, calculated from wavefront aberrations recorded over time during experimental trials. The tested conditions were as follows: Correction of all the subject's aberrations except defocus (C); Correction of all the subject's aberrations except defocus and habitual second‐order astigmatism (AS); Correction of all the subject's aberrations except defocus and odd higher‐order aberrations (HOAs); Correction of all the subject's aberrations except defocus and even HOAs (E); Natural aberrations of the subject's eye, i.e., the adaptive‐optics system only corrected the optical system's aberrations (N); Correction of all the subject's aberrations except defocus and fourth‐order spherical aberration (SA). The correction was performed at 20 Hz and each condition was repeated six times in randomised order. Results Average gain (±2 standard errors of the mean) varied little across conditions; between 0.55 ± 0.06 (SA), and 0.62 ± 0.06 (AS). Average phase (±2 standard errors of the mean) also varied little; between 0.41 ± 0.02 s (E), and 0.47 ± 0.02 s (O). After Bonferroni correction, no statistically significant differences in gain or phase were found in the presence of specific monochromatic aberrations or in their absence. Conclusions These results show that the eye's monochromatic aberrations are not necessary for accommodation to track dynamic accommodative stimuli.
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Affiliation(s)
- Paula Bernal-Molina
- Departamento de Óptica y Optometría y Ciencias de la Visión, Facultad de Física, Universidad de Valencia, Burjassot, Spain.,Laboratorio Interuniversitario de Investigación en Visión y Optometría - Unidad Mixta UVEG-UMU, Valencia-Murcia, Spain
| | - Iván Marín-Franch
- Departamento de Óptica y Optometría y Ciencias de la Visión, Facultad de Física, Universidad de Valencia, Burjassot, Spain.,Laboratorio Interuniversitario de Investigación en Visión y Optometría - Unidad Mixta UVEG-UMU, Valencia-Murcia, Spain
| | - Antonio J Del Águila-Carrasco
- Departamento de Óptica y Optometría y Ciencias de la Visión, Facultad de Física, Universidad de Valencia, Burjassot, Spain.,Laboratorio Interuniversitario de Investigación en Visión y Optometría - Unidad Mixta UVEG-UMU, Valencia-Murcia, Spain
| | - Jose J Esteve-Taboada
- Departamento de Óptica y Optometría y Ciencias de la Visión, Facultad de Física, Universidad de Valencia, Burjassot, Spain.,Laboratorio Interuniversitario de Investigación en Visión y Optometría - Unidad Mixta UVEG-UMU, Valencia-Murcia, Spain
| | - Norberto López-Gil
- Laboratorio Interuniversitario de Investigación en Visión y Optometría - Unidad Mixta UVEG-UMU, Valencia-Murcia, Spain.,Instituto Universitario de Investigación en Envejecimiento, Universidad de Murcia, Murcia, Spain
| | - Philip B Kruger
- Department of Biological & Vision Sciences, State University of New York, State College of Optometry, New York, USA
| | - Robert Montés-Micó
- Departamento de Óptica y Optometría y Ciencias de la Visión, Facultad de Física, Universidad de Valencia, Burjassot, Spain.,Laboratorio Interuniversitario de Investigación en Visión y Optometría - Unidad Mixta UVEG-UMU, Valencia-Murcia, Spain
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27
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Litts KM, Cooper RF, Duncan JL, Carroll J. Photoreceptor-Based Biomarkers in AOSLO Retinal Imaging. Invest Ophthalmol Vis Sci 2017; 58:BIO255-BIO267. [PMID: 28873135 PMCID: PMC5584616 DOI: 10.1167/iovs.17-21868] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 07/28/2017] [Indexed: 01/08/2023] Open
Abstract
Improved understanding of the mechanisms underlying inherited retinal degenerations has created the possibility of developing much needed treatments for these relentless, blinding diseases. However, standard clinical indicators of retinal health (such as visual acuity and visual field sensitivity) are insensitive measures of photoreceptor survival. In many retinal degenerations, significant photoreceptor loss must occur before measurable differences in visual function are observed. Thus, there is a recognized need for more sensitive outcome measures to assess therapeutic efficacy as numerous clinical trials are getting underway. Adaptive optics (AO) retinal imaging techniques correct for the monochromatic aberrations of the eye and can be used to provide nearly diffraction-limited images of the retina. Many groups routinely are using AO imaging tools to obtain in vivo images of the rod and cone photoreceptor mosaic, and it now is possible to monitor photoreceptor structure over time with single cell resolution. Highlighting recent work using AO scanning light ophthalmoscopy (AOSLO) across a range of patient populations, we review the development of photoreceptor-based metrics (e.g., density/geometry, reflectivity, and size) as candidate biomarkers. Going forward, there is a need for further development of automated tools and normative databases, with the latter facilitating the comparison of data sets across research groups and devices. Ongoing and future clinical trials for inherited retinal diseases will benefit from the improved resolution and sensitivity that multimodal AO retinal imaging affords to evaluate safety and efficacy of emerging therapies.
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Affiliation(s)
- Katie M. Litts
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Robert F. Cooper
- Department of Psychology, University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Jacque L. Duncan
- Department of Ophthalmology, University of California, San Francisco, California, United States
| | - Joseph Carroll
- Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
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28
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Dong ZM, Wollstein G, Wang B, Schuman JS. Adaptive optics optical coherence tomography in glaucoma. Prog Retin Eye Res 2017; 57:76-88. [PMID: 27916682 PMCID: PMC5350038 DOI: 10.1016/j.preteyeres.2016.11.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 11/14/2016] [Accepted: 11/19/2016] [Indexed: 02/07/2023]
Abstract
Since the introduction of commercial optical coherence tomography (OCT) systems, the ophthalmic imaging modality has rapidly expanded and it has since changed the paradigm of visualization of the retina and revolutionized the management and diagnosis of neuro-retinal diseases, including glaucoma. OCT remains a dynamic and evolving imaging modality, growing from time-domain OCT to the improved spectral-domain OCT, adapting novel image analysis and processing methods, and onto the newer swept-source OCT and the implementation of adaptive optics (AO) into OCT. The incorporation of AO into ophthalmic imaging modalities has enhanced OCT by improving image resolution and quality, particularly in the posterior segment of the eye. Although OCT previously captured in-vivo cross-sectional images with unparalleled high resolution in the axial direction, monochromatic aberrations of the eye limit transverse or lateral resolution to about 15-20 μm and reduce overall image quality. In pairing AO technology with OCT, it is now possible to obtain diffraction-limited resolution images of the optic nerve head and retina in three-dimensions, increasing resolution down to a theoretical 3 μm3. It is now possible to visualize discrete structures within the posterior eye, such as photoreceptors, retinal nerve fiber layer bundles, the lamina cribrosa, and other structures relevant to glaucoma. Despite its limitations and barriers to widespread commercialization, the expanding role of AO in OCT is propelling this technology into clinical trials and onto becoming an invaluable modality in the clinician's arsenal.
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Affiliation(s)
- Zachary M Dong
- University of Pittsburgh Medical Center (UPMC) Eye Center, Eye and Ear Institute, Department of Ophthalmology, University of Pittsburgh School of Medicine, Ophthalmology and Visual Science Research Center, Pittsburgh, PA, United States.
| | - Gadi Wollstein
- New York University (NYU) Langone Eye Center, NYU Langone Medical Center, Department of Ophthalmology, NYU School of Medicine, New York, NY, United States.
| | - Bo Wang
- University of Pittsburgh Medical Center (UPMC) Eye Center, Eye and Ear Institute, Department of Ophthalmology, University of Pittsburgh School of Medicine, Ophthalmology and Visual Science Research Center, Pittsburgh, PA, United States.
| | - Joel S Schuman
- New York University (NYU) Langone Eye Center, NYU Langone Medical Center, Department of Ophthalmology, NYU School of Medicine, New York, NY, United States; Department of Electrical and Computer Engineering, New York University Tandon School of Engineering, Brooklyn, NY, United States.
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29
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Mariotti L, Devaney N, Lombardo G, Lombardo M. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years. BIOMEDICAL OPTICS EXPRESS 2016; 7:2807-22. [PMID: 27446708 PMCID: PMC4948632 DOI: 10.1364/boe.7.002807] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 05/12/2016] [Accepted: 05/12/2016] [Indexed: 05/18/2023]
Abstract
Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation.
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Affiliation(s)
- Letizia Mariotti
- Applied Optics Group, School of Physics, National University of Ireland, Galway,
Ireland
| | - Nicholas Devaney
- Applied Optics Group, School of Physics, National University of Ireland, Galway,
Ireland
| | - Giuseppe Lombardo
- Istituto per i Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche, Viale F. Stagno D’Alcontres 37, 98158, Messina,
Italy
- Vision Engineering Italy srl, Via Adda 7, 00198 Rome,
Italy
| | - Marco Lombardo
- Fondazione G.B. Bietti IRCCS, Via Livenza 3, 00198 Rome,
Italy
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Ramamirtham R, Akula JD, Soni G, Swanson MJ, Bush JN, Moskowitz A, Swanson EA, Favazza TL, Tavormina JL, Mujat M, Ferguson RD, Hansen RM, Fulton AB. Extrafoveal Cone Packing in Eyes With a History of Retinopathy of Prematurity. Invest Ophthalmol Vis Sci 2016; 57:467-75. [PMID: 26868749 PMCID: PMC4758295 DOI: 10.1167/iovs.15-17783] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Purpose To study the density and packing geometry of the extrafoveal cone photoreceptors in eyes with a history of retinopathy of prematurity (ROP). We used a multimodal combination of adaptive optics (AO) scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT). Methods Cones were identified in subjects (aged 14–26 years) with a history of ROP that was either severe and treated by laser ablation of avascular peripheral retina (TROP; n = 5) or mild and spontaneously resolved, untreated (UROP; n = 5), and in term-born controls (CT; n = 8). The AO-SLO images were obtained at temporal eccentricities 4.5°, 9°, 13.5°, and 18° using both confocal and offset apertures with simultaneous, colocal OCT images. Effects of group, eccentricity, and aperture were evaluated and the modalities compared. Results In the SLO images, cone density was lower and the packing pattern less regular in TROP, relative to CT and UROP retinae. Although SLO image quality appeared lower in TROP, root mean square (RMS) wavefront error did not differ among the groups. In TROP eyes, cone discrimination was easier in offset aperture images. There was no evidence of cone loss in the TROP OCT images. Conclusions Low cone density in TROP confocal SLO images may have resulted from lower image quality. Since AO correction in these eyes was equivalent to that of the control group, and OCT imaging showed no significant cone loss, the optical properties of the inner retina or properties of the cones themselves are likely altered in a way that affects photoreceptor imaging.
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Affiliation(s)
- Ramkumar Ramamirtham
- Boston Children's Hospital, Boston, Massachusetts, United States 2Harvard Medical School, Boston, Massachusetts, United States
| | - James D Akula
- Boston Children's Hospital, Boston, Massachusetts, United States 2Harvard Medical School, Boston, Massachusetts, United States
| | - Garima Soni
- Boston Children's Hospital, Boston, Massachusetts, United States 3Northeastern University, Boston, Massachusetts, United States
| | - Matthew J Swanson
- Boston Children's Hospital, Boston, Massachusetts, United States 4Air Force Academy, Colorado, United States
| | - Jennifer N Bush
- Boston Children's Hospital, Boston, Massachusetts, United States
| | - Anne Moskowitz
- Boston Children's Hospital, Boston, Massachusetts, United States 2Harvard Medical School, Boston, Massachusetts, United States
| | - Emily A Swanson
- Boston Children's Hospital, Boston, Massachusetts, United States
| | - Tara L Favazza
- Boston Children's Hospital, Boston, Massachusetts, United States
| | - Jena L Tavormina
- Boston Children's Hospital, Boston, Massachusetts, United States
| | - Mircea Mujat
- Physical Sciences, Inc., Andover, Massachusetts, United States
| | | | - Ronald M Hansen
- Boston Children's Hospital, Boston, Massachusetts, United States 2Harvard Medical School, Boston, Massachusetts, United States
| | - Anne B Fulton
- Boston Children's Hospital, Boston, Massachusetts, United States 2Harvard Medical School, Boston, Massachusetts, United States
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Morris HJ, Blanco L, Codona JL, Li SL, Choi SS, Doble N. Directionality of individual cone photoreceptors in the parafoveal region. Vision Res 2015; 117:67-80. [PMID: 26494187 DOI: 10.1016/j.visres.2015.10.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 10/02/2015] [Accepted: 10/03/2015] [Indexed: 11/29/2022]
Abstract
The pointing direction of cone photoreceptors can be inferred from the Stiles-Crawford Effect of the First Kind (SCE-I) measurement. Healthy retinas have tightly packed cones with a SCE-I function peak either centered in the pupil or with a slight nasal bias. Various retinal pathologies can change the profile of the SCE-I function implying that the arrangement or the light capturing properties of the cone photoreceptors are affected. Measuring the SCE-I may reveal early signs of photoreceptor change before actual cell apoptosis occurs. In vivo retinal imaging with adaptive optics (AO) was used to measure the pointing direction of individual cones at eight retinal locations in four control human subjects. Retinal images were acquired by translating an aperture in the light delivery arm through 19 different locations across a subject's entrance pupil. Angular tuning properties of individual cones were calculated by fitting a Gaussian to the reflected intensity profile of each cone projected onto the pupil. Results were compared to those from an accepted psychophysical SCE-I measurement technique. The maximal difference in cone directionality of an ensemble of cones, ρ¯, between the major and minor axes of the Gaussian fit was 0.05 versus 0.29mm(-2) in one subject. All four subjects were found to have a mean nasal bias of 0.81mm with a standard deviation of ±0.30mm in the peak position at all retinal locations with mean ρ¯ value decreasing by 23% with increasing retinal eccentricity. Results show that cones in the parafoveal region converge towards the center of the pupillary aperture, confirming the anterior pointing alignment hypothesis.
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Affiliation(s)
- Hugh J Morris
- College of Optometry, The Ohio State University, 338 West Tenth Avenue, Columbus, OH 43210, USA.
| | - Leonardo Blanco
- College of Optometry, The Ohio State University, 338 West Tenth Avenue, Columbus, OH 43210, USA.
| | - Johanan L Codona
- Steward Observatory, University of Arizona, Tucson, AZ 85721, USA.
| | - Simone L Li
- Laboratory of Visual and Ocular Motor Physiology, Akron Children's Hospital, Akron, OH 44224, USA.
| | - Stacey S Choi
- College of Optometry, The Ohio State University, 338 West Tenth Avenue, Columbus, OH 43210, USA.
| | - Nathan Doble
- College of Optometry, The Ohio State University, 338 West Tenth Avenue, Columbus, OH 43210, USA.
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Carrasco-Zevallos O, Nankivil D, Keller B, Viehland C, Lujan BJ, Izatt JA. Pupil tracking optical coherence tomography for precise control of pupil entry position. BIOMEDICAL OPTICS EXPRESS 2015; 6:3405-19. [PMID: 26417510 PMCID: PMC4574666 DOI: 10.1364/boe.6.003405] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/10/2015] [Accepted: 08/12/2015] [Indexed: 05/20/2023]
Abstract
To maximize the collection efficiency of back-scattered light, and to minimize aberrations and vignetting, the lateral position of the scan pivot of an optical coherence tomography (OCT) retinal scanner should be imaged to the center of the ocular pupil. Additionally, several retinal structures including Henle's Fiber Layer (HFL) exhibit reflectivities that depend on illumination angle, which can be controlled by varying the pupil entry position of the OCT beam. In this work, we describe an automated method for controlling the lateral pupil entry position in retinal OCT by utilizing pupil tracking in conjunction with a 2D fast steering mirror placed conjugate to the retinal plane. We demonstrate that pupil tracking prevents lateral motion artifacts from impeding desired pupil entry locations, and enables precise pupil entry positioning and therefore control of the illumination angle of incidence at the retinal plane. We use our prototype pupil tracking OCT system to directly visualize the obliquely oriented HFL.
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Affiliation(s)
- Oscar Carrasco-Zevallos
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
| | - Derek Nankivil
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
| | - Brenton Keller
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
| | - Christian Viehland
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
| | - Brandon J. Lujan
- Department of Vision Science, School of Optometry, University of California, Berkeley, CA 94701, USA
- West Coast Retina Medical Group, San Francisco, CA 94109, USA
| | - Joseph A. Izatt
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
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Ziccardi L, Giannini D, Lombardo G, Serrao S, Dell'Omo R, Nicoletti A, Bertelli M, Lombardo M. Multimodal Approach to Monitoring and Investigating Cone Structure and Function in an Inherited Macular Dystrophy. Am J Ophthalmol 2015; 160:301-312.e6. [PMID: 25908487 DOI: 10.1016/j.ajo.2015.04.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Revised: 04/11/2015] [Accepted: 04/14/2015] [Indexed: 12/30/2022]
Abstract
PURPOSE To examine a female subject, her father, and a brother harboring a missense mutation of the retinitis pigmentosa 1-like 1 (RP1L1) gene, over 2 years of follow-up. DESIGN Observational case series. METHODS setting: Fondazione G.B. Bietti IRCCS, Rome, Italy. STUDY POPULATION RP1L1 family members and controls. MAIN OUTCOME MEASURES Images of the cone mosaic acquired with an adaptive optics retinal camera, spectral-domain optical coherence tomography (SD OCT), and full-field and multifocal electroretinography (mfERG). RESULTS In the proband, best-corrected visual acuity (≤0.7 logMAR) was stable in both eyes during follow-up, though analysis of adaptive optics images showed decreased cone density in the central 9 degrees from the fovea with respect to controls (P < .05) and cone density loss in the parafoveal area (2 degrees; <12%-16%) during follow-up. Texture analysis of SD OCT images identified abnormalities of the ellipsoid zone in the central 7 degrees, while mfERG response amplitudes were reduced only in the central 5 degrees relative to controls. In the proband's father, who had 0.0 logMAR visual acuity, significant cone loss was found in the central 7 degrees from the fovea (P < .05); abnormal SD OCT and mfERG values with respect to controls were found in corresponding retinal areas. No defects in the cone structure and function were found in the proband's brother, who had 0.0 logMAR visual acuity. CONCLUSIONS Occult macular dystrophy was diagnosed based on genetic and multimodal ophthalmic findings. The quantitative assessment of photoreceptor survival or loss, based on analysis of adaptive optics retinal images, was valuable to monitor disease progression at a cellular level.
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