Journal articles: 'Functional retinal imaging'

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Ganekal, Sunil. "Retinal functional imager (RFI): Non-invasive functional imaging of the retina." Nepalese Journal of Ophthalmology 5, no. 2 (September 25, 2013): 250–57. http://dx.doi.org/10.3126/nepjoph.v5i2.8738.

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Retinal functional imager (RFI) is a unique non-invasive functional imaging system with novel capabilities for visualizing the retina. The objective of this review was to show the utility of non-invasive functional imaging in various disorders. Electronic literature search was carried out using the websites www.pubmed.gov and www.google.com. The search words were retinal functional imager and non-invasive retinal imaging used in combination. The articles published or translated into English were studied. The RFI directly measures hemodynamic parameters such as retinal blood-flow velocity, oximetric state, metabolic responses to photic activation and generates capillary perfusion maps (CPM) that provides retinal vasculature detail similar to flourescein angiography. All of these parameters stand in a direct relationship to the function and therefore the health of the retina, and are known to be degraded in the course of retinal diseases. Detecting changes in retinal function aid early diagnosis and treatment as functional changes often precede structural changes in many retinal disorders. Nepal J Ophthalmol 2013; 5(10): 250-257 DOI: http://dx.doi.org/10.3126/nepjoph.v5i2.8738

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Hunter, Jennifer J., William H. Merigan, and Jesse B. Schallek. "Imaging Retinal Activity in the Living Eye." Annual Review of Vision Science 5, no. 1 (September 15, 2019): 15–45. http://dx.doi.org/10.1146/annurev-vision-091517-034239.

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Retinal function has long been studied with psychophysical methods in humans, whereas detailed functional studies of vision have been conducted mostly in animals owing to the invasive nature of physiological approaches. There are exceptions to this generalization, for example, the electroretinogram. This review examines exciting recent advances using in vivo retinal imaging to understand the function of retinal neurons. In some cases, the methods have existed for years and are still being optimized. In others, new methods such as optophysiology are revealing novel patterns of retinal function in animal models that have the potential to change our understanding of the functional capacity of the retina. Together, the advances in retinal imaging mark an important milestone that shifts attention away from anatomy alone and begins to probe the function of healthy and diseased eyes.

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Yao, Xincheng, Taeyoon Son, Tae-Hoon Kim, and Yiming Lu. "Functional optical coherence tomography of retinal photoreceptors." Experimental Biology and Medicine 243, no. 17-18 (November 27, 2018): 1256–64. http://dx.doi.org/10.1177/1535370218816517.

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Age-related macular degeneration (AMD) is the leading cause of severe vision loss and legal blindness. It is known that retinal photoreceptors are the primary target of AMD. Therefore, a reliable method for objective assessment of photoreceptor function is needed for early detection and reliable treatment evaluation of AMD and other eye diseases such as retinitis pigmentosa that are known to cause photoreceptor dysfunctions. Stimulus-evoked intrinsic optical signal (IOS) changes promise a unique opportunity for objective assessment of physiological function of retinal photoreceptor and inner neurons. Instead of a comprehensive review, this mini-review is to provide a brief summary of our recent in vitro and in vivo optical coherence tomography (OCT) studies of stimulus-evoked IOS changes in animal retinas. By providing excellent axial resolution to differentiate individual retinal layers, depth-resolved OCT revealed rapid IOS response at the photoreceptor outer segment. The fast photoreceptor-IOS occurred almost right away (∼ 2 ms) after the onset of retinal stimulation, differentiating itself from slow IOS changes correlated with inner neural and hemodynamic changes. Further development of the functional IOS instruments and retinal stimulation protocols may provide a feasible solution to pursue clinical application of functional IOS imaging for objective assessment of human photoreceptors. Impact statement Retinal photoreceptors are the primary target of age-related macular degeneration (AMD) which is the leading cause of severe vision loss and legal blindness. An objective method for functional assessment of photoreceptor physiology can benefit early detection and better treatment evaluation of AMD and other eye diseases that are known to cause photoreceptor dysfunctions. This article summarizes in vitro study of IOS mechanisms and in vivo demonstration of IOS imaging of intact animals. Further development of the functional IOS imaging may provide a revolutionary solution to achieve objective assessment of human photoreceptors.

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Barliya, Tilda, Ron Ofri, Shai Sandalon, Dov Weinberger, and Tami Livnat. "Changes in Retinal Function and Cellular Remodeling Following Experimental Retinal Detachment in a Rabbit Model." Journal of Ophthalmology 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/4046597.

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Purpose.To explore functional electroretinographic (ERG) changes and associated cellular remodeling following experimental retinal detachment in a rabbit model.Methods.Retinal detachment was created in ten rabbits by injecting 0.1 ml balanced salt solution under the retina. Fundus imaging was performed 0, 3, 7, 14, and 21 days postoperatively. ERGs were recorded pre- and 7 and 21 days postoperatively. Eyes were harvested on day 21 and evaluated immunohistochemically (IHC) for remodeling of second- and third-order neurons.Results.Retinal reattachment occurred within two weeks following surgery. No attenuation was observed in the photopic or scotopic a- and b-waves. A secondary wavefront on the descending slope of the scotopic b-wave was the only ERG result that was attenuated in detached retinas. IHC demonstrated anatomical changes in both ON and OFF bipolar cells. Bassoon staining was observed in the remodeled dendrites. Amacrine and horizontal cells did not alter, but Muller cells were clearly reactive with marked extension.Conclusion.Retinal detachment and reattachment were associated with functional and anatomical changes. Exploring the significance of the secondary scotopic wavefront and its association with the remodeling of 2nd- and 3rd-order neurons will shade more light on functional changes and recovery of the retina.

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Azuma, Shinnosuke, Shuichi Makita, Deepa Kasaragod, Satoshi Sugiyama, Masahiro Miura, and Yoshiaki Yasuno. "Clinical multi-functional OCT for retinal imaging." Biomedical Optics Express 10, no. 11 (October 14, 2019): 5724. http://dx.doi.org/10.1364/boe.10.005724.

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Nguyen, Van, and Yannis Paulus. "Photoacoustic Ophthalmoscopy: Principle, Application, and Future Directions." Journal of Imaging 4, no. 12 (December 12, 2018): 149. http://dx.doi.org/10.3390/jimaging4120149.

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Photoacoustic ophthalmoscopy (PAOM) is a novel, hybrid, non-ionizing, and non-invasive imaging technology that has been used to assess the retina. PAOM can provide both anatomic and functional retinal characterizations with high resolution, high sensitivity, high contrast, and a high depth of penetration. Thus, ocular diseases can be precisely detected and visualized at earlier stages, resulting in an improved understanding of pathophysiology, improved management, and the improved monitoring of retinal treatment to prevent vision loss. To better visualize ocular components such as retinal vessels, choroidal vessels, choroidal neovascularization, retinal neovascularization, and the retinal pigment epithelium, an advanced multimodal ocular imaging platform has been developed by a combination of PAOM with other optical imaging techniques such as optical coherence tomography (OCT), scanning laser ophthalmoscopy (SLO), and fluorescence microscopy. The multimodal images can be acquired from a single imaging system and co-registered on the same image plane, enabling an improved evaluation of disease. In this review, the potential application of photoacoustic ophthalmoscopy in both research and clinical diagnosis are discussed as a medical screening technique for the visualization of various ocular diseases. The basic principle and requirements of photoacoustic ocular imaging are introduced. Then, various photoacoustic microscopy imaging systems of the retina in animals are presented. Finally, the future development of PAOM and multimodal imaging is discussed.

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Hugo, Juliette, Marie Beylerian, Eric Denion, Aurore Aziz, Pierre Gascon, Danièle Denis, and Frédéric Matonti. "Multimodal imaging of torpedo maculopathy including adaptive optics." European Journal of Ophthalmology 30, no. 2 (February 8, 2019): NP27—NP31. http://dx.doi.org/10.1177/1120672119827772.

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Purpose: The etiology of torpedo maculopathy remains unknown, but it has been recently suggested that it could represent a persistent defect in the development of the retinal pigment epithelium. As retinal pigment epithelium and photoreceptors form a functional unit, an alteration of photoreceptor distribution or function is predictable. The aim of this study is to describe multimodal imaging, including adaptive optics, in three cases of torpedo maculopathy, and discuss its pathogenesis. Methods: Multimodal imaging is presented, including fundus photographs, optical coherence tomography, adaptive optics, autofluorescence, fluorescein angiography, and ultra-widefield retinal imaging in three cases of torpedo maculopathy. Results: An oval-shaped well-delimited chorioretinal lesion both hypopigmented centrally and with a hyperpigmented border in the temporal macula, consistent with torpedo maculopathy, was observed in three patients. Optical coherence tomography showed a preservation of the inner retina, a mild atrophy of the outer retina, an alteration of the ellipsoid zone and of the retinal pigment epithelium layer, and a neurosensory detachment. These lesions were hypoautofluorescent with a hyperautofluorescent border. Fluorescein angiography showed a hyperfluorescence by window effect. Adaptive optics imaging showed an alteration of the cone mosaic within the lesions, with a lower cone density and a higher spacing between cones. Conclusion: The alteration of the cone mosaic suggested by adaptive optics in torpedo maculopathy has never been described and could be explained by the alteration of the retinal pigment epithelium. Our results support the existing hypothesis on the pathogenesis of torpedo maculopathy that a persistent defect in the development of the retinal pigment epithelium may be responsible for this clinical entity.

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Gao, Guanjie, Liwen He, Shengxu Liu, Dandan Zheng, Xiaojing Song, Wenxin Zhang, Minzhong Yu, Guangwei Luo, and Xiufeng Zhong. "Establishment of a Rapid Lesion-Controllable Retinal Degeneration Monkey Model for Preclinical Stem Cell Therapy." Cells 9, no. 11 (November 13, 2020): 2468. http://dx.doi.org/10.3390/cells9112468.

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Background: Retinal degenerative disorders (RDs) are the main cause of blindness without curable treatment. Our previous studies have demonstrated that human-induced pluripotent stem cells can differentiate into retinal organoids with all subtypes of retina, which provides huge promise for treating these diseases. Before these methods can be realized, RD animal models are required to evaluate the safety and efficacy of stem cell therapy and to develop the surgical tools and procedures for cell transplantation in patients. This study involved the development of a monkey model of RD with controllable lesion sites, which can be rapidly prepared for the study of preclinical stem cell therapy among other applications. Methods: Sodium nitroprusside (SNP) in three doses was delivered into the monkey eye by subretinal injection (SI), and normal saline was applied as control. Structural and functional changes of the retinas were evaluated via multimodal imaging techniques and multifocal electroretinography (mfERG) before and after the treatment. Histological examination was performed to identify the target layer of the affected retina. The health status of monkeys was monitored during the experiment. Results: Well-defined lesions with various degrees of retinal degeneration were induced at the posterior pole of retina as early as 7 days after SNP SI. The damage of SNP was dose dependent. In general, 0.05 mM SNP caused mild structural changes in the retina; 0.1 mM SNP led to the loss of outer retinal layers, including the outer plexiform layer (OPL), outer nuclear layer (ONL), and retinal pigment epithelium (RPE); while 0.2 mM SNP impacted the entire layer of the retina and choroid. MfERG showed reduced amplitude in the damaged region. The structural and functional damages were not recovered at 7-month follow-up. Conclusion: A rapidly induced lesion site-controllable retinal degeneration monkey model was established by the subretinal administration of SNP, of which the optimal dose is 0.1 mM. This monkey model mimics the histological changes of advanced RDs and provides a valuable platform for preclinical assessment of stem cell therapy for RDs.

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Yao, Xincheng, and Tae-Hoon Kim. "Fast intrinsic optical signal correlates with activation phase of phototransduction in retinal photoreceptors." Experimental Biology and Medicine 245, no. 13 (June 19, 2020): 1087–95. http://dx.doi.org/10.1177/1535370220935406.

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Quantitative assessment of physiological condition of retinal photoreceptors is desirable for better detection and treatment evaluation of eye diseases that can cause photoreceptor dysfunctions. Functional intrinsic optical signal (IOS) imaging, also termed as optoretinography (ORG) or optophysiology, has been proposed as a high-resolution method for objective assessment of retinal physiology. Fast IOS in retinal photoreceptors shows a time course earlier than that of electroretinography a-wave, promising an objective marker for noninvasive ORG of early phototransduction process in retinal photoreceptors. In this article, recent observations of fast photoreceptor-IOS in animal and human retinas are summarized, and the correlation of fast photoreceptor-IOS to five steps of phototransduction process is discussed. Transient outer segment conformational change, due to inter-disc space shrinkage correlated with activation phase of phototransduction, has been disclosed as a primary source of the fast photoreceptor-IOS. Impact statement As the center of phototransduction, retinal photoreceptors are responsible for capturing and converting photon energy to bioelectric signals for following visual information processing in the retina. This article summarizes experimental observation and discusses biophysical mechanism of fast photoreceptor-intrinsic optical signal (IOS) correlated with early phase of phototransduction. Quantitative imaging of fast photoreceptor-IOS may provide objective optoretinography to advance the study and diagnosis of age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy, and other eye diseases that can cause photoreceptor dysfunctions.

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de Carvalho, Emanuel R., Richelle J. M. Hoveling, Cornelis J. F. van Noorden, Reinier O. Schlingemann, and Maurice C. G. Aalders. "Functional Imaging of the Ocular Fundus Using an 8-Band Retinal Multispectral Imaging System." Instruments 4, no. 2 (May 7, 2020): 12. http://dx.doi.org/10.3390/instruments4020012.

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Application of functional imaging in ophthalmology requires efficient imaging techniques that can detect and quantify chromophores to visualise processes in vivo. The aim of the present study was to develop and evaluate a fast and affordable imaging system. We describe an eight-band retinal multispectral imaging (MSI) system and compare it with a hyperspectral imaging (HSI) device. Determination of blood oxygen saturation was studied as proof of principle. Reflectance of incident light is measured as 1/absorbance at different wavelengths between 440 nm and 580 nm. Both devices have incorporated optical bandpass filters in a mydriatic fundus camera. The MSI system scans the retina at eight pre-defined wavelengths specific for the spectrum of haemoglobin. The HSI system acquires a full scan from 480 to 720 nm in 5 nm steps. A simple assessment of the ratio between the absorbance peaks of oxygenated haemoglobin (HbO2) and reduced haemoglobin (HbR) was not suitable for generating validated oxygenation maps of the retina. However, a correction algorithm that compares the measured reflectance with reflectance spectra of fully oxygenated and fully deoxygenated blood allowed our MSI setup to estimate relative oxygen saturation at higher levels, but underestimated relative oxygen saturation at lower levels. The MSI device generated better quality images than the HSI device. It allows customisation with filter sets optimised for other chromophores of interest, and augmented with extrinsic contrast imaging agents, it has the potential for a wider range of ophthalmic molecular imaging applications.

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Zhuang, Xiaonan, Zhongcui Sun, Fengjuan Gao, Min Wang, Wenyi Tang, Wei Liu, Keyan Wang, Jihong Wu, Rui Jiang, and Gezhi Xu. "Ocular Manifestations in a Chinese Pedigree of Familial Amyloidotic Polyneuropathy Carrying the Transthyretin Mutation c.401A>G (p.Tyr134Cys)." Genes 13, no. 5 (May 16, 2022): 886. http://dx.doi.org/10.3390/genes13050886.

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Familial amyloid polyneuropathy (FAP) caused by a genetic mutation in transthyretin (TTR) is an autosomal dominant hereditary disease. The retrospective, observational case series study presents the ocular clinicopathological findings of five cases carrying the TTR mutation c.401A>G (p.Tyr134Cys). Multimodal retinal imaging and electrophysiological examination, Congo red staining and immunohistochemical analysis of specimens, and genetic analyses were performed. Cases 1 and 2 were symptomatic with vitreous and retinal amyloid deposition and poor visual recovery. Case 3 had a symptomatic vitreous haze in the left eye with good postoperative visual recovery. The right eye of case 3 and the eyes of cases 4 and 5 were asymptomatic. Thicker retinal nerve fiber layer, retinal venous tortuosity with prolonged arteriovenous passage time on fluorescein angiography and retinal dysfunction detected by multifocal electroretinogram occurred even in asymptomatic eyes. Moreover, the internal limiting membrane from patients with FAP was stained positive for Congo red and transforming growth factor-β1. The results highlight the amyloid deposition of mutant TTR in the optic disc and retina, even in the asymptomatic stage. The deposited amyloid leads to increased resistance to venous return and retinal functional abnormalities. Therefore, careful follow-up of structural and functional changes in the retina is needed, even in asymptomatic patients with FAP.

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Heisler-Taylor, Tyler, Richard Wan, Elizabeth G. Urbanski, Sumaya Hamadmad, Mohd Hussain Shah, Hailey Wilson, Julie Racine, and Colleen M. Cebulla. "Multimodal imaging and functional analysis of the chick NMDA retinal damage model." PLOS ONE 16, no. 9 (September 7, 2021): e0257148. http://dx.doi.org/10.1371/journal.pone.0257148.

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Objectives The chick is rapidly becoming a standardized preclinical model in vision research to study mechanisms of ocular disease. We seek to comprehensively evaluate the N-methyl-D-aspartate (NMDA) model of excitotoxic retinal damage using multimodal imaging, functional, and histologic approaches in NMDA-damaged, vehicle-treated, and undamaged chicks. Methods Chicks were either left undamaged in both eyes or were injected with NMDA in the left eye and saline (vehicle) in the right eye. TUNEL assay was performed on chicks to assess levels of retinal cell death one day post-injection of NMDA or saline and on age-matched untreated chicks. Spectral domain optical coherence tomography (SD-OCT) was performed weekly on chicks and age-matched controls day 1 (D1) up to D28 post-injection. Light adapted electroretinograms (ERG) were performed alongside SD-OCT measurements on post-injection chicks along with age-matched untreated controls. Results Untreated and vehicle-treated eyes had no TUNEL positive cells while NMDA-treated eyes accumulated large numbers of TUNEL positive cells in the Inner Nuclear Layer (INL), but not other layers, at D1 post injection. Significant inner retina swelling or edema was found on SD-OCT imaging at D1 post-injection which resolved at subsequent timepoints. Both the INL and the inner plexiform layer significantly thinned by one-week post-injection and did not recover for the duration of the measurements. On ERG, NMDA-treated eyes had significantly reduced amplitudes of all parameters at D1 with all metrics improving over time. The b-wave, oscillatory potentials, and ON/OFF bipolar responses were the most affected with at least 70% reduction immediately after damage compared to the fellow eye control. Conclusion This study establishes a normative baseline on the retinal health and gross functional ability as well as intraocular pressures of undamaged, vehicle-treated, and NMDA-damaged chicks to provide a standard for comparing therapeutic treatment studies in this important animal model.

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BARNARD, ALUN R., JOANNE M. APPLEFORD, SUMATHI SEKARAN, KRISHNA CHINTHAPALLI, AARON JENKINS, MATHEAS SEELIGER, MARTIN BIEL, et al. "Residual photosensitivity in mice lacking both rod opsin and cone photoreceptor cyclic nucleotide gated channel 3 α subunit." Visual Neuroscience 21, no. 5 (September 2004): 675–83. http://dx.doi.org/10.1017/s0952523804215024.

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The mammalian retina contains three classes of photoreceptor. In addition to the rods and cones, a subset of retinal ganglion cells that express the putative sensory photopigment melanopsin are intrinsically photosensitive. Functional and anatomical studies suggest that these inner retinal photoreceptors provide light information for a number of non-image-forming light responses including photoentrainment of the circadian clock and the pupil light reflex. Here, we employ a newly developed mouse model bearing lesions of both rod and cone phototransduction cascades (Rho−/−Cnga3−/−) to further examine the function of these non-rod non-cone photoreceptors. Calcium imaging confirms the presence of inner retinal photoreceptors inRho−/−Cnga3−/−mice. Moreover, these animals retain a pupil light reflex, photoentrainment, and light induction of the immediate early genec-fosin the suprachiasmatic nuclei, consistent with previous findings that pupillary and circadian responses can employ inner retinal photoreceptors.Rho−/−Cnga3−/−mice also show a light-dependent increase in the number of FOS-positive cells in both the ganglion cell and (particularly) inner nuclear layers of the retina. The average number of cells affected is several times greater than the number of melanopsin-positive cells in the mouse retina, suggesting functional intercellular connections from these inner retinal photoreceptors within the retina. Finally, however, while we show that wild types exhibit an increase in heart rate upon light exposure, this response is absent inRho−/−Cnga3−/−mice. Thus, it seems that non-rod non-cone photoreceptors can drive many, but not all, non-image-forming light responses.

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Almonte, Melanie T., Pamela Capellàn, Timothy E. Yap, and Maria Francesca Cordeiro. "Retinal correlates of psychiatric disorders." Therapeutic Advances in Chronic Disease 11 (January 2020): 204062232090521. http://dx.doi.org/10.1177/2040622320905215.

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Diagnosis and monitoring of psychiatric disorders rely heavily on subjective self-reports of clinical symptoms, which are complicated by the varying consistency of accounts reported by patients with an impaired mental state. Hence, more objective and quantifiable measures have been sought to provide clinicians with more robust methods to evaluate symptomology and track progression of disease in response to treatments. Owing to the shared origins of the retina and the brain, it has been suggested that changes in the retina may correlate with structural and functional changes in the brain. Vast improvements in retinal imaging, namely optical coherence tomography (OCT) and electrodiagnostic technology, have made it possible to investigate the eye at a microscopic level, allowing for the investigation of potential biomarkers in vivo. This review provides a summary of retinal biomarkers associated with schizophrenia, bipolar disorder and major depression, demonstrating how retinal biomarkers may be used to complement existing methods and provide structural markers of pathophysiological mechanisms that underpin brain dysfunction in psychiatric disorders.

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Minnella, Angelo Maria, Roberta Rissotto, Martina Maceroni, Angela Romano, Romina Fasciani, Marco Luigetti, Mario Sabatelli, Stanislao Rizzo, and Benedetto Falsini. "Ocular Involvement in Hereditary Transthyretin Amyloidosis: A Case Series Describing Novel Potential Biomarkers." Genes 12, no. 6 (June 18, 2021): 927. http://dx.doi.org/10.3390/genes12060927.

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Hereditary transthyretin amyloidosis (hATTR) is a rare disease caused by a point mutation in the transthyretin (TTR) gene and inherited in an autosomal dominant fashion. TTR is a plasma protein that functions as a carrier for thyroxine (T4) and retinol (vitamin A). Ophthalmological manifestations are due to both the hepatic and ocular production of mutated TTR. In this case series, we report the ocular manifestations of hATTR in eighteen eyes of nine consecutive patients. Corneal nerve abnormalities as well as morphological and functional changes in the retina were investigated. The study was a single-center, retrospective, observational, clinical case series. In all patients, corneal confocal microscopy (CCM), multimodal imaging of the retina, including fundus photography and Optical Coherence Tomography (OCT), as well as rod and cone electroretinography (ERG) were performed. Eight patients had active disease and one was an unaffected carrier. In all study eyes, corneal nerve plexa examined with CCM were poorly represented or absent. Mixed rod-cone and cone ERG b-wave amplitudes were reduced, and photopic b-wave responses were significantly delayed. Photopic Negative Response (PhNR) amplitude was significantly reduced, while PhNR latency was significantly augmented. In 13/18 eyes, vitreous opacities and abnormalities of vitreo-retinal interface were found. The current results highlight the presence of corneal nerve damage. Functional retinal abnormalities, detected by ERG, can be found even in the presence of minimal or absent structural retinal damage. These findings support the use of CCM and ERGs to detect early biomarkers for primary hATTR.

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DOU, PENG, YANG ZHANG, RUI ZHENG, YU YE, JIANBO MAO, LEI LIU, MING WU, and MINGZHAI SUN. "RETINAL IMAGING AND ANALYSIS USING MACHINE LEARNING WITH INFORMATION FUSION OF THE FUNCTIONAL AND STRUCTURAL FEATURES BASED ON A DUAL-MODAL FUNDUS CAMERA." Journal of Mechanics in Medicine and Biology 21, no. 06 (June 2, 2021): 2150030. http://dx.doi.org/10.1142/s0219519421500305.

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Retinal diseases and systemic diseases, such as diabetic retinopathy (DR) and Alzheimer’s disease, may manifest themselves in the retina, changing the retinal oxygen saturation ([Formula: see text]) level or the retinal vascular structures. Recent studies explored the correlation of diseases with either retina vascular structures or [Formula: see text] level, but not both due to the lack of proper instrument or methodology. In this study, we applied a dual-modal fundus camera and developed a deep learning-based analysis method to simultaneously acquire and quantify the [Formula: see text] and vascular structures. Deep learning was used to automatically locate the optic discs and segment arterioles and venules of the blood vessels. We then sought to apply machine learning methods, such as random forest (RF) and support vector machine (SVM), to fuse the [Formula: see text] level and retinal vessel parameters as different features to discriminate against the disease from the healthy controls. We showed that the fusion of the functional (oxygen saturation) and structural (vascular parameters) features offers better performance to classify diseased and healthy subjects. For example, we gained a 13.8% and 2.0% increase in the accuracy with fusion using the RF and SVM to classify the nonproliferative DR and the healthy controls.

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Ochi, Ryosuke, Bunpei Sato, Masashi Mimura, Seita Morishita, Masanori Fukumoto, Teruyo Kida, Jun Sugasawa, and Tsunehiko Ikeda. "A Case of Coats' Disease with Spontaneous Retinal Reattachment after Total Detachment." Case Reports in Ophthalmology 6, no. 2 (June 23, 2015): 200–203. http://dx.doi.org/10.1159/000434676.

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Purpose: To report a case of Coats' disease in which spontaneous reattachment occurred after total retinal detachment. Patient and Methods: A young boy (patient age: 4 years and 11 months) presented with leukocoria in the left eye. Slit-lamp examination revealed total retinal detachment with abnormal retinal blood vessels and subretinal exudation just behind the lens. Computed tomography imaging showed no solid mass lesion in the intraocular space. Secondary total retinal detachment as a complication of Coats' disease was diagnosed. No light perception was detected, so we determined that surgical treatment was not indicated. Results: Four months after the initial diagnosis, the retina showed complete reattachment with a large amount of subretinal hard exudate. Visual acuity remained unchanged, with no light perception. Conclusions: We speculate that the spontaneous retinal reattachment in the present case was caused by the decreased permeability of the abnormal retinal vessels and the good functional effect of the retinal pigment epithelium.

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Bernardes,, Rui, Pedro Serranho, Torcato Santos, Valter Gonçalves, and José Cunha Vaz. "Optical Coherence Tomography ? Automatic Retina Classification Through Support Vector Machines." European Ophthalmic Review 06, no. 04 (2012): 200. http://dx.doi.org/10.17925/eor.2012.06.04.200.

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Optical coherence tomography (OCT) is becoming one of the most important imaging modalities in ophthalmology due to its non-invasiveness and by allowing the visualisation the human retina structure in detail. It was recently proposed that OCT data embeds functional information from the human retina. Specifically, it was proposed that blood-retinal barrier status information is present within OCT data from the human retina. Besides this ability, the authors present data supporting the idea of having the OCT data encoding the ageing of the retina in addition to the disease (diabetes) condition from the healthy status. The methodology followed makes use of a supervised classification procedure, the support vector machine (SVM) classifier – based solely on the statistics of the distribution of OCT data from the human retina (i.e. OCT data between the inner limiting membrane and the retinal pigment epithelium). Results achieved suggest that information on both the healthy status of the blood–retinal barrier and on the ageing process co-exist encoded within the optical properties of the human retina.

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Chen, Andrew X., Thais F. Conti, Grant L. Hom, Tyler E. Greenlee, Raffaele Raimondi, Isaac N. Briskin, Collin A. Rich, et al. "Functional imaging of mitochondria in retinal diseases using flavoprotein fluorescence." Eye 35, no. 1 (July 24, 2020): 74–92. http://dx.doi.org/10.1038/s41433-020-1110-y.

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Urrea-Victoria, Tatiana, Emiliano Fulda-Graue, Miguel A. Quiroz-Reyes, Felipe Esparza-Correa, Alejandra Nieto-Jordan, Erick A. Quiroz-Gonzalez, and Federico Graue-Wiechers. "Postoperative Multimodal Analysis in Successful Gas Displacement of a Submacular Hemorrhage." Case Reports in Ophthalmological Medicine 2021 (June 3, 2021): 1–7. http://dx.doi.org/10.1155/2021/5577826.

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In this report, we describe a case of timely gas vitrectomy to displace a moderate submacular hemorrhage from the submacular space without tPA, release vitreoretinal traction along the borders of a posterior retinal tear, and analyze postoperative multimodal imaging findings in a 34-year-old male patient whose right eye was injured by a stone. The patient underwent a successful nontissue plasminogen activator gas vitrectomy 3 days after the accident. A multimodal evaluation with spectral-domain optical coherence tomography (SD-OCT), 10-2 and 30-2 campimetry, microperimetry, multifocal electroretinography (mfERG), and visual evoked potentials was performed 6 months after the accident. The multimodal imaging tests yielded abnormal foveal SD-OCT patterns, with a fibrous sealed tear in the retinal pigment epithelium. Campimetry showed low levels of retinal sensitivity; microperimetry and mfERG revealed a subnormal retinal response and a reduction in the N1 and P1 wave amplitudes. The visual evoked potential responses were normal. Multidisciplinary examination at 6 months postoperatively revealed a structurally and functionally abnormal macula. The retina remained attached. Our functional findings indicate that submacular hemorrhage should be treated in a timely manner to minimize photoreceptor damage.

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Yin, Lu, Ying Geng, Fumitaka Osakada, Robin Sharma, Ali H. Cetin, Edward M. Callaway, David R. Williams, and William H. Merigan. "Imaging light responses of retinal ganglion cells in the living mouse eye." Journal of Neurophysiology 109, no. 9 (May 1, 2013): 2415–21. http://dx.doi.org/10.1152/jn.01043.2012.

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This study reports development of a novel method for high-resolution in vivo imaging of the function of individual mouse retinal ganglion cells (RGCs) that overcomes many limitations of available methods for recording RGC physiology. The technique combines insertion of a genetically encoded calcium indicator into RGCs with imaging of calcium responses over many days with FACILE (functional adaptive optics cellular imaging in the living eye). FACILE extends the most common method for RGC physiology, in vitro physiology, by allowing repeated imaging of the function of each cell over many sessions and by avoiding damage to the retina during removal from the eye. This makes it possible to track changes in the response of individual cells during morphological development or degeneration. FACILE also overcomes limitations of existing in vivo imaging methods, providing fine spatial and temporal detail, structure-function comparison, and simultaneous analysis of multiple cells.

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Lockhart, C. J., A. J. McCann, R. A. Pinnock, P. K. Hamilton, M. T. Harbinson, and G. E. McVeigh. "Multimodal functional and anatomic imaging identifies preclinical microvascular abnormalities in type 1 diabetes mellitus." American Journal of Physiology-Heart and Circulatory Physiology 307, no. 12 (December 15, 2014): H1729—H1736. http://dx.doi.org/10.1152/ajpheart.00372.2014.

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Structural and functional changes in the microcirculation in type 1 diabetes mellitus predict future end-organ damage and macrovascular events. We explored the utility of novel signal processing techniques to detect and track changes in ocular hemodynamics in patients with this disease. Twenty-four patients with uncomplicated type 1 diabetes mellitus and eighteen age- and sex-matched control subjects were studied. Doppler ultrasound was used to interrogate the carotid and ophthalmic arteries, and digital photography was used to image the retinal vasculature. Frequency analysis algorithms were applied to quantify velocity waveform structure and retinal photographic data at baseline and after inhalation of 100% O2. Frequency data were compared between groups. No significant differences were found in the resistive index between groups at baseline or after inhaled O2. Frequency analysis of Doppler flow velocity waveforms identified significant differences in bands 3–7 between patients and control subjects in data captured from the ophthalmic artery ( P < 0.01 for each band). In response to inhaled O2, changes in frequency band amplitudes were significantly greater in control subjects compared with patients ( P < 0.05). Only control subjects demonstrated a positive correlation ( R = 0.61) between changes in retinal vessel diameter and frequency band amplitudes derived from ophthalmic artery waveform data. The use of multimodal signal processing techniques applied to Doppler flow velocity waveforms and retinal photographic data identified preclinical changes in the ocular microcirculation in patients with uncomplicated diabetes mellitus. An impaired autoregulatory response of the retinal microvasculature may contribute to the future development of retinopathy in such patients.

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Brown, Brian. "Structural and functional imaging of the retina: new ways to diagnose and assess retinal disease*." Clinical and Experimental Optometry 91, no. 6 (November 2008): 504–14. http://dx.doi.org/10.1111/j.1444-0938.2008.00322.x.

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Ts’o, Daniel, Jesse Schallek, Young Kwon, Randy Kardon, Michael Abramoff, and Peter Soliz. "Noninvasive functional imaging of the retina reveals outer retinal and hemodynamic intrinsic optical signal origins." Japanese Journal of Ophthalmology 53, no. 4 (July 2009): 334–44. http://dx.doi.org/10.1007/s10384-009-0687-2.

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An, Lin, Bixuan Yan, Yansong Zhao, Ke He, Xiaocui Wu, Gongpu Lan, Yanping Huang, et al. "Pulsatile retinal nerve fiber layer imaging with functional optical coherence tomography." Optics Continuum 1, no. 2 (February 3, 2022): 283. http://dx.doi.org/10.1364/optcon.450978.

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Yang, Jee Myung, KyungA Yun, Jehwi Jeon, Hae Young Yang, Bora Kim, Sunhong Jeong, Junyeop Lee, et al. "Multimodal evaluation of an interphotoreceptor retinoid-binding protein-induced mouse model of experimental autoimmune uveitis." Experimental & Molecular Medicine 54, no. 3 (March 2022): 252–62. http://dx.doi.org/10.1038/s12276-022-00733-z.

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AbstractWe aimed to characterize the vascular phenotypes of an experimental autoimmune retinal uveitis (EAU) model induced by interphotoreceptor retinoid-binding protein (IRBP) using multimodal imaging techniques. We systemically administered IRBP or vehicle to adult C57BL/6 mice. Fundus photography, optical coherence tomography (OCT), in vivo live confocal imaging using different tracers, OCT angiography (OCTA), and electroretinography (ERG) were performed after IRBP immunization. Hematoxylin and eosin and immunofluorescence staining were performed to characterize the immune response and vascular permeability. Mice with EAU exhibited perivascular inflammation, vitritis, and superficial retinal inflammation on fundus photography and OCT. H&E revealed immune cell infiltration in the perivascular area of the retina and choroid accompanied by a significant degree of perivasculitis that subsequently damaged photoreceptors 3 weeks postimmunization. Immunofluorescence staining showed subsequent transcytosis induction after local microglial activation followed by neutrophil recruitment in the perivascular area. Transcytosis in the superficial and deep vascular areas was improved by immune cell suppression. Intravital in vivo confocal imaging showed signs of neutrophil infiltration and obstructive vasculitis with perivascular leakage 3 weeks postimmunization. OCTA revealed a significant decrease in vascular flow in the deep capillary layer of the retina. Functional analysis showed that scotopic responses were intact at 2 weeks; however, normal photopic and scotopic responses were hardly detected in mice with EAU mice at 3 weeks postimmunization. Our data suggest that inflammatory cell activation and subsequent transcytosis induction in endothelial cells might be a major pathogenic factor for vascular leakage in uveitis, providing new insights into the pathophysiology of retinal vasculitis in noninfectious uveitis.

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Lin, Tai-Chi, Magdalene J. Seiler, Danhong Zhu, Paulo Falabella, David R. Hinton, Dennis O. Clegg, Mark S. Humayun, and Biju B. Thomas. "Assessment of Safety and Functional Efficacy of Stem Cell-Based Therapeutic Approaches Using Retinal Degenerative Animal Models." Stem Cells International 2017 (2017): 1–19. http://dx.doi.org/10.1155/2017/9428176.

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Dysfunction and death of retinal pigment epithelium (RPE) and or photoreceptors can lead to irreversible vision loss. The eye represents an ideal microenvironment for stem cell-based therapy. It is considered an “immune privileged” site, and the number of cells needed for therapy is relatively low for the area of focused vision (macula). Further, surgical placement of stem cell-derived grafts (RPE, retinal progenitors, and photoreceptor precursors) into the vitreous cavity or subretinal space has been well established. For preclinical tests, assessments of stem cell-derived graft survival and functionality are conducted in animal models by various noninvasive approaches and imaging modalities.In vivoexperiments conducted in animal models based on replacing photoreceptors and/or RPE cells have shown survival and functionality of the transplanted cells, rescue of the host retina, and improvement of visual function. Based on the positive results obtained from these animal experiments, human clinical trials are being initiated. Despite such progress in stem cell research, ethical, regulatory, safety, and technical difficulties still remain a challenge for the transformation of this technique into a standard clinical approach. In this review, the current status of preclinical safety and efficacy studies for retinal cell replacement therapies conducted in animal models will be discussed.

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CHEUNG, SING-HANG, and GORDON E. LEGGE. "Functional and cortical adaptations to central vision loss." Visual Neuroscience 22, no. 2 (March 2005): 187–201. http://dx.doi.org/10.1017/s0952523805222071.

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Age-related macular degeneration (AMD), affecting the retina, afflicts one out of ten people aged 80 years or older in the United States. AMD often results in vision loss to the central 15–20 deg of the visual field (i.e. central scotoma), and frequently afflicts both eyes. In most cases, when the central scotoma includes the fovea, patients will adopt an eccentric preferred retinal locus (PRL) for fixation. The onset of a central scotoma results in the absence of retinal inputs to corresponding regions of retinotopically mapped visual cortex. Animal studies have shown evidence for reorganization in adult mammals for such cortical areas following experimentally induced central scotomata. However, it is still unknown whether reorganization occurs in primary visual cortex (V1) of AMD patients. Nor is it known whether the adoption of a PRL corresponds to changes to the retinotopic mapping of V1. Two recent advances hold out the promise for addressing these issues and for contributing to the rehabilitation of AMD patients: improved methods for assessing visual function across the fields of AMD patients using the scanning laser ophthalmoscope, and the advent of brain-imaging methods for studying retinotopic mapping in humans. For the most part, specialists in these two areas come from different disciplines and communities, with few opportunities to interact. The purpose of this review is to summarize key findings on both the clinical and neuroscience issues related to questions about visual adaptation in AMD patients.

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Xue, Yuntian, Magdalene J. Seiler, William C. Tang, Jasmine Y. Wang, Jeffrey Delgado, Bryce T. McLelland, Gabriel Nistor, Hans S. Keirstead, and Andrew W. Browne. "Retinal organoids on-a-chip: a micro-millifluidic bioreactor for long-term organoid maintenance." Lab on a Chip 21, no. 17 (2021): 3361–77. http://dx.doi.org/10.1039/d1lc00011j.

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Yap, Timothy E., Shiama I. Balendra, Melanie T. Almonte, and M. Francesca Cordeiro. "Retinal correlates of neurological disorders." Therapeutic Advances in Chronic Disease 10 (January 2019): 204062231988220. http://dx.doi.org/10.1177/2040622319882205.

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Considering the retina as an extension of the brain provides a platform from which to study diseases of the nervous system. Taking advantage of the clear optical media of the eye and ever-increasing resolution of modern imaging techniques, retinal morphology can now be visualized at a cellular level in vivo. This has provided a multitude of possible biomarkers and investigative surrogates that may be used to identify, monitor and study diseases until now limited to the brain. In many neurodegenerative conditions, early diagnosis is often very challenging due to the lack of tests with high sensitivity and specificity, but, once made, opens the door to patients accessing the correct treatment that can potentially improve functional outcomes. Using retinal biomarkers in vivo as an additional diagnostic tool may help overcome the need for invasive tests and histological specimens, and offers the opportunity to longitudinally monitor individuals over time. This review aims to summarise retinal biomarkers associated with a range of neurological conditions including Alzheimer’s disease (AD), Parkinson’s disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and prion diseases from a clinical perspective. By comparing their similarities and differences according to primary pathological processes, we hope to show how retinal correlates can aid clinical decisions, and accelerate the study of this rapidly developing area of research.

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Giuffrè, Chiara, Elisabetta Miserocchi, Alessandro Marchese, Maria Vittoria Cicinelli, Elena Bruschi, Giuseppe Querques, Francesco M. Bandello, and Giulio M. Modorati. "Widefield OCT angiography and ultra-widefield multimodal imaging of Susac syndrome." European Journal of Ophthalmology 30, no. 5 (April 10, 2019): NP41—NP45. http://dx.doi.org/10.1177/1120672119843281.

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The aim is to present the changes in ultra-widefield and widefield multimodal imaging, including optical coherence tomography angiography of a 33-year-old woman diagnosed with Susac syndrome, over 1 year of follow-up. Fundus examination and multimodal imaging revealed bilateral arterial occlusion of multiple vascular branches with retinal ischemia. Over 1 year follow-up, best-corrected visual acuity improved while retinal ischemia gradually resolved. Widefield optical coherence tomography angiography showed reperfusion of macular large vessels, but not of the small capillaries. Despite anatomical improvement, functional defects of the visual field persisted. In conclusion, widefield and ultra-widefield imaging provided high-resolution details of the central and peripheral damages in Susac syndrome.

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Campagnoli, Thalmon R., Gábor Márk Somfai, Jing Tian, Delia Cabrera DeBuc, and William E. Smiddy. "Noninvasive, High-Resolution Functional Macular Imaging in Subjects With Retinal Vein Occlusion." Ophthalmic Surgery, Lasers and Imaging Retina 48, no. 10 (October 1, 2017): 799–809. http://dx.doi.org/10.3928/23258160-20170928-04.

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Azimipour, Mehdi, Justin V. Migacz, Robert J. Zawadzki, John S. Werner, and Ravi S. Jonnal. "Functional retinal imaging using adaptive optics swept-source OCT at 16 MHz." Optica 6, no. 3 (March 5, 2019): 300. http://dx.doi.org/10.1364/optica.6.000300.

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Mac Grory, Brian, Matthew Schrag, Sven Poli, Chantal J. Boisvert, Martin S. Spitzer, Maximillian Schultheiss, Max Nedelmann, et al. "Structural and Functional Imaging of the Retina in Central Retinal Artery Occlusion – Current Approaches and Future Directions." Journal of Stroke and Cerebrovascular Diseases 30, no. 7 (July 2021): 105828. http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2021.105828.

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Campagnoli, Thalmon R., Jing Tian, Delia Cabrera DeBuc, and William E. Smiddy. "Exploratory study of non-invasive, high-resolution functional macular imaging in subjects with diabetic retinopathy." International Journal of Ophthalmology 14, no. 1 (January 18, 2021): 57–63. http://dx.doi.org/10.18240/ijo.2021.01.08.

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AIM: To evaluate a high-resolution functional imaging device that yields quantitative data regarding macular blood flow and capillary network features in eyes with diabetic retinopathy (DR). METHODS: Prospective, cross-sectional comparative case-series in which blood flow velocities (BFVs) and non-invasive capillary perfusion maps (nCPMs) in macular vessels were measured in patients with DR and in healthy controls using the Retinal Functional Imager (RFI) device. RESULTS: A total of 27 eyes of 21 subjects were studied [9 eyes nonproliferative diabetic retinopathy (NPDR), 9 eyes proliferative diabetic retinopathy (PDR) and 9 controls]. All diabetic patients were type 2. All patients with NPDR and 5 eyes with PDR also had diabetic macular edema (DME). The NPDR group included eyes with severe (n=3) and moderate NPDR (n=6), and were symptomatic. A significant decrease in venular BFVs was observed in the macular region of PDR eyes when compared to controls (2.61±0.6 mm/s and 2.92±0.72 mm/s in PDR and controls, respectively, P=0.019) as well as PDR eyes with DME compared to NPDR eyes (2.36±0.51 mm/s and 2.94±1.09 mm/s in PDR with DME and NPDR, respectively, P=0.01). CONCLUSION: The RFI, a non-invasive imaging tool, provides high-resolution functional imaging of the retinal microvasculature and quantitative measurement of BFVs in visually impaired DR patients. The isolated diminish venular BFVs in PDR eyes compared to healthy eyes and PDR eyes with DME in comparison to NPDR eyes may indicate the possibility of more retinal vein compromise than suspected in advanced DR.

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Bassetto, Marco, Daniel Ajoy, Florent Poulhes, Cathy Obringer, Aurelie Walter, Nadia Messadeq, Amir Sadeghi, et al. "Magnetically Assisted Drug Delivery of Topical Eye Drops Maintains Retinal Function In Vivo in Mice." Pharmaceutics 13, no. 10 (October 9, 2021): 1650. http://dx.doi.org/10.3390/pharmaceutics13101650.

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Barded-Biedl syndrome (BBS) is a rare genetic disorder with an unmet medical need for retinal degeneration. Small-molecule drugs were previously identified to slow down the apoptosis of photoreceptors in BBS mouse models. Clinical translation was not practical due to the necessity of repetitive invasive intravitreal injections for pediatric populations. Non-invasive methods of retinal drug targeting are a prerequisite for acceptable adaptation to the targeted pediatric patient population. Here, we present the development and functional testing of a non-invasive, topical, magnetically assisted delivery system, harnessing the ability of magnetic nanoparticles (MNPs) to cargo two drugs (guanabenz and valproic acid) with anti-unfolded protein response (UPR) properties towards the retina. Using magnetic resonance imaging (MRI), we showed the MNPs’ presence in the retina of Bbs wild-type mice, and their photoreceptor localization was validated using transmission electron microscopy (TEM). Subsequent electroretinogram recordings (ERGs) demonstrated that we achieved beneficial biological effects with the magnetically assisted treatment translating the maintained light detection in Bbs−/− mice (KO). To our knowledge, this is the first demonstration of efficient magnetic drug targeting in the photoreceptors in vivo after topical administration. This non-invasive, needle-free technology expands the application of SMDs for the treatment of a vast spectrum of retinal degenerations and other ocular diseases.

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Zhang, Ling-Li, Eric Delpire, and Noga Vardi. "NKCC1 Does Not Accumulate Chloride in Developing Retinal Neurons." Journal of Neurophysiology 98, no. 1 (July 2007): 266–77. http://dx.doi.org/10.1152/jn.00288.2007.

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GABA excites immature neurons due to their relatively high intracellular chloride concentration. This initial high concentration is commonly attributed to the ubiquitous chloride cotransporter NKCC1, which uses a sodium gradient to accumulate chloride. Here we tested this hypothesis in immature retinal amacrine and ganglion cells. Western blotting detected NKCC1 at birth and its expression first increased, then decreased to the adult level. Immunocytochemistry confirmed this early expression of NKCC1 and localized it to all nuclear layers. In the ganglion cell layer, staining peaked at P4 and then decreased with age, becoming undetectable in adult. In comparison, KCC2, the chloride extruder, steadily increased with age localizing primarily to the synaptic layers. For functional tests, we used calcium imaging with fura-2 and chloride imaging with 6-methoxy- N-ethylquinolinium iodide. If NKCC1 accumulates chloride in ganglion and amacrine cells, deleting or blocking it should abolish the GABA-evoked calcium rise. However, at P0-5 GABA consistently evoked a calcium rise that was not abolished in the NKCC1-null retinas, nor by applying high concentrations of bumetanide (NKCC blocker) for long periods. Furthermore, intracellular chloride concentration in amacrine and ganglion cells of the NKCC1-null retinas was ∼30 mM, same as in wild type at this age. This concentration was not lowered by applying bumetanide or by decreasing extracellular sodium concentration. Costaining for NKCC1 and cellular markers suggested that at P3, NKCC1 is restricted to Müller cells. We conclude that NKCC1 does not serve to accumulate chloride in immature retinal neurons, but it may enable Müller cells to buffer extracellular chloride.

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Godat, Tyler, Nicolas P. Cottaris, Sara Patterson, Kendall Kohout, Keith Parkins, Qiang Yang, Jennifer M. Strazzeri, et al. "In vivo chromatic and spatial tuning of foveolar retinal ganglion cells in Macaca fascicularis." PLOS ONE 17, no. 11 (November 29, 2022): e0278261. http://dx.doi.org/10.1371/journal.pone.0278261.

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The primate fovea is specialized for high acuity chromatic vision, with the highest density of cone photoreceptors and a disproportionately large representation in visual cortex. The unique visual properties conferred by the fovea are conveyed to the brain by retinal ganglion cells, the somas of which lie at the margin of the foveal pit. Microelectrode recordings of these centermost retinal ganglion cells have been challenging due to the fragility of the fovea in the excised retina. Here we overcome this challenge by combining high resolution fluorescence adaptive optics ophthalmoscopy with calcium imaging to optically record functional responses of foveal retinal ganglion cells in the living eye. We use this approach to study the chromatic responses and spatial transfer functions of retinal ganglion cells using spatially uniform fields modulated in different directions in color space and monochromatic drifting gratings. We recorded from over 350 cells across three Macaca fascicularis primates over a time period of weeks to months. We find that the majority of the L vs. M cone opponent cells serving the most central foveolar cones have spatial transfer functions that peak at high spatial frequencies (20–40 c/deg), reflecting strong surround inhibition that sacrifices sensitivity at low spatial frequencies but preserves the transmission of fine detail in the retinal image. In addition, we fit to the drifting grating data a detailed model of how ganglion cell responses draw on the cone mosaic to derive receptive field properties of L vs. M cone opponent cells at the very center of the foveola. The fits are consistent with the hypothesis that foveal midget ganglion cells are specialized to preserve information at the resolution of the cone mosaic. By characterizing the functional properties of retinal ganglion cells in vivo through adaptive optics, we characterize the response characteristics of these cells in situ.

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Asanad, Samuel, Isa Mohammed, Alfredo A. Sadun, and Osamah J. Saeedi. "OCTA in neurodegenerative optic neuropathies: emerging biomarkers at the eye–brain interface." Therapeutic Advances in Ophthalmology 12 (January 2020): 251584142095050. http://dx.doi.org/10.1177/2515841420950508.

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Optical coherence tomography angiography (OCTA) is an emerging technique for non-invasively imaging the ocular vasculature, enabling quantitative measurements of retinal vascular anatomy. As extensions of the central nervous system, the optic nerve and the retina share many vascular characteristics with the brain. Measuring the structural and functional changes within the ocular vasculature may be useful as an objective approach for non-invasively evaluating the cerebrovascular architecture. The current article reviews the most recent applications of OCTA imaging at the eye-brain interface and highlights the emerging vascular biomarkers for neurodegenerative optic neuropathies, as reported in Alzheimer’s disease, Parkinson’s disease, schizophrenia, and mitochondrial optic neuropathies. These ophthalmologic findings offer objective measures of a more accessible clinical marker and may improve our understanding of neurodegenerative disease.

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Schneider, Colleen L., Emily K. Prentiss, Ania Busza, Kelly Matmati, Nabil Matmati, Zoë R. Williams, Bogachan Sahin, and Bradford Z. Mahon. "Survival of retinal ganglion cells after damage to the occipital lobe in humans is activity dependent." Proceedings of the Royal Society B: Biological Sciences 286, no. 1897 (February 27, 2019): 20182733. http://dx.doi.org/10.1098/rspb.2018.2733.

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Damage to the optic radiations or primary visual cortex leads to blindness in all or part of the contralesional visual field. Such damage disconnects the retina from its downstream targets and, over time, leads to trans-synaptic retrograde degeneration of retinal ganglion cells. To date, visual ability is the only predictor of retinal ganglion cell degeneration that has been investigated after geniculostriate damage. Given prior findings that some patients have preserved visual cortex activity for stimuli presented in their blind field, we tested whether that activity explains variability in retinal ganglion cell degeneration over and above visual ability. We prospectively studied 15 patients (four females, mean age = 63.7 years) with homonymous visual field defects secondary to stroke, 10 of whom were tested within the first two months after stroke. Each patient completed automated Humphrey visual field testing, retinotopic mapping with functional magnetic resonance imaging, and spectral-domain optical coherence tomography of the macula. There was a positive relation between ganglion cell complex (GCC) thickness in the blind field and early visual cortex activity for stimuli presented in the blind field. Furthermore, residual visual cortex activity for stimuli presented in the blind field soon after the stroke predicted the degree of retinal GCC thinning six months later. These findings indicate that retinal ganglion cell survival after ischaemic damage to the geniculostriate pathway is activity dependent.

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Gao, Qing, Bin Peng, Xin Huang, Chen-Xing Qi, Yan Tong, Qin-Qin Deng, and Yin Shen. "Assessment of cerebral low-frequency oscillations in patients with retinal vein occlusion: a preliminary functional MRI study." Acta Radiologica 61, no. 6 (October 11, 2019): 813–20. http://dx.doi.org/10.1177/0284185119879683.

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Background There is increasing evidence that patients with retinal vein occlusion exhibit cerebral vascular changes and are at an increased risk of stroke. However, it remains unknown whether patients with retinal vein occlusion exhibit changes in intrinsic brain activity. Purpose This study investigated intrinsic brain activity changes in patients with retinal vein occlusion by assessing the amplitude of low-frequency fluctuations. Material and Methods Forty-five patients with retinal vein occlusion (22 men, 23 women, mean age 56.55 ± 6.97 years) and 43 healthy controls (13 men, 30 women; mean age 53.53 ± 8.19 years) closely matched in age, sex, and education level underwent resting-state MRI scans. The amplitude of low-frequency fluctuation method was used to compare intrinsic brain activity between the two groups. Results Compared with healthy controls, patients with retinal vein occlusion exhibited significantly lower amplitude of low-frequency fluctuation values in the left middle occipital gyrus, right middle occipital gyrus, and right calcarine. However, patients with retinal vein occlusion showed significantly higher amplitude of low-frequency fluctuations in the bilateral cerebellum 6, right hippocampus, left insula, and left fusiform (voxel-level P < 0.01, Gaussian random field correction, cluster-level P < 0.05). Conclusion Our results demonstrated that patients with retinal vein occlusion showed abnormal spontaneous neural activities in the visual cortices, cerebellum, and Papez circuit, which might indicate impaired vision, cognition, and emotional function in patients with retinal vein occlusion. These findings offer important insights into the neural mechanism of retinal vein occlusion.

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Li, Xuefeng, Tao Li, Li Yang, and Long-Yun Li. "Protective roles of ketamine and xylazine against lightinduced retinal degeneration in rats." Tropical Journal of Pharmaceutical Research 18, no. 4 (May 18, 2021): 727–33. http://dx.doi.org/10.4314/tjpr.v18i4.7.

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Purpose: To study the protective effects of ketamine and xylazine against light exposure-induced retinal degeneration (RD) in rats. Methods: Sprague Dawley rats were divided into three groups viz: light damage before anesthesia (LAE), light damage only (LDO), and control (CON) group which was kept in the dark for 12 - 18 h to habituate before light exposure. LDO group was exposed to light before anesthesia, while LAE group was maintained under anesthesia with ketamine and xylazine. The groups were kept for 120 min in darkness after anesthesia prior to light exposure and they were awakened prior to light damage. Functional assessment was carried out using electroretinography while morphological analysis was carried out using histology and immunochemistry techniques. Results: Ketamine-xylazine combination preserved the function of the retina and protected against light-induced RD based on retinal imaging studies and immunochemistry analysis. Xylazine and ketamine anesthesia provided protection against light-induced retinal damage, and thus reduced photoreceptor cell death. Conclusion: These results indicate that xylazine and ketamine anesthesia offer protection against lightinduced damage and photoreceptor cell death in rats, and therefore, can potentially be developed for use in humans.

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Kung, Frank H., and Ellen Townes-Anderson. "Creating Custom Neural Circuits on Multiple Electrode Arrays Utilizing Optical Tweezers for Precise Nerve Cell Placement." Methods and Protocols 3, no. 2 (June 20, 2020): 44. http://dx.doi.org/10.3390/mps3020044.

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Precise creation, maintenance, and monitoring of neuronal circuits would facilitate the investigation of subjects such as neuronal development or synaptic plasticity, or assist in the development of neuronal prosthetics. Here we present a method to precisely control the placement of multiple types of neuronal retinal cells onto a commercially available multiple electrode array (MEA), using custom-built optical tweezers. We prepared the MEAs by coating a portion of the MEA with a non-adhesive substrate (Poly (2-hydroxyethyl methacrylate)), and the electrodes with an adhesive cell growth substrate. We then dissociated the retina of adult tiger salamanders, plated them onto prepared MEAs, and utilized the optical tweezers to create retinal circuitry mimicking in vivo connections. In our hands, the optical tweezers moved ~75% of photoreceptors, bipolar cells, and multipolar cells, an average of ~2000 micrometers, at a speed of ~16 micrometers/second. These retinal circuits were maintained in vitro for seven days. We confirmed electrophysiological activity by stimulating the photoreceptors with the MEA and measuring their response with calcium imaging. In conclusion, we have developed a method of utilizing optical tweezers in conjunction with MEAs that allows for the design and maintenance of custom neural circuits for functional analysis.

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Sahel, José-Alain, Kate Grieve, Chloé Pagot, Colas Authié, Saddek Mohand-Said, Michel Paques, Isabelle Audo, et al. "Assessing Photoreceptor Status in Retinal Dystrophies: From High-Resolution Imaging to Functional Vision." American Journal of Ophthalmology 230 (October 2021): 12–47. http://dx.doi.org/10.1016/j.ajo.2021.04.013.

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Fechtig, Daniel J., Branislav Grajciar, Tilman Schmoll, Cedric Blatter, Rene M. Werkmeister, Wolfgang Drexler, and Rainer A. Leitgeb. "Line-field parallel swept source MHz OCT for structural and functional retinal imaging." Biomedical Optics Express 6, no. 3 (February 4, 2015): 716. http://dx.doi.org/10.1364/boe.6.000716.

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Mihashi, T., Y. Hirohara, Y. Kitaguchi, T. Morimoto, T. Miyoshi, and T. Fujikado. "Differences in the independent components in two-spectral-band for retinal functional imaging." Journal of Vision 9, no. 14 (December 1, 2009): 88. http://dx.doi.org/10.1167/9.14.88.

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Faure, Céline, Kiyoko Gocho, Yannick Le Mer, José Alain Sahel, Michel Paques, and Isabelle Audo. "Functional and high resolution retinal imaging assessment in a case of ocular siderosis." Documenta Ophthalmologica 128, no. 1 (December 13, 2013): 69–75. http://dx.doi.org/10.1007/s10633-013-9421-y.

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Audo, Isabelle, Kiyoko Gocho, Florence Rossant, Saddek Mohand-Saïd, Kevin Loquin, Isabelle Bloch, José-Alain Sahel, and Michel Paques. "Functional and high-resolution retinal imaging monitoring photoreceptor damage in acute macular neuroretinopathy." Graefe's Archive for Clinical and Experimental Ophthalmology 254, no. 5 (September 7, 2015): 855–64. http://dx.doi.org/10.1007/s00417-015-3136-6.

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Kogoleva, Ludmila V., and Elena N. Demchenko. "CLINICAL MANIFESTATIONS AND OUTCOMES OF RETINAL HEMORRHAGES IN INFANTS: A CASE SERIES." Current pediatrics 17, no. 2 (May 22, 2018): 133–37. http://dx.doi.org/10.15690/vsp.v17i2.1879.

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Background. Retinal hemorrhages in infants are frequent pathologies, but their causes, clinical forms and functional outcomes are poorly studied. The study of hemorrhage localization in the eye structure, time frames of their resolution, and the long-term effects that may affect the development of vision is of particular interest.Objective. Our aim was to analyze clinical forms, time frames of resolution and long-term clinical and functional outcomes of retinal hemorrhages in infants.Methods. All children with retinal hemorrhages, who applied to a premature baby room in the MRI of ED n. a. Helmholtz at the age from 3 weeks to 3 months for 5 years (2011–2015), were examined using indirect ophthalmoscopy. In case of extensive lesions, the process dynamics was controlled by a pediatric digital retinal imaging system. Long-term clinical and functional outcomes of retinal hemorrhages were studied using ultrasound examination and spectral optical coherence tomography.Results. Fundus hemorrhages were revealed in 108 (5.9%) of 1,825 infants on 142 eyes (34 children had bilateral hemorrhages). Hemorrhages were more frequent in children delivered vaginally (79 children, 73.2%), were unilateral (74 children, 63.5%), pre-retinal (108 eyes, 76.1%), of central localization (119 eyes, 83.8%). The time frames of hemorrhage resolution in 53 children (49.1%) were more than one month. Long-term outcomes of retinal hemorrhages were studied in 22 children (33 eyes) at the age of 2–5 years. Residual changes in the structure of the neuroepithelium and vitreoretinal interface with a decrement in visual acuity were noted in 7 children (9 eyes).Conclusion. Retinal hemorrhages of newborns are characterized by clinical polymorphism, different time frames of resolution and outcomes, which requires a case follow-up.

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Chiang, Tsun-Kang, Kayla Marie White, Shree K. Kurup, and Minzhong Yu. "Use of Visual Electrophysiology to Monitor Retinal and Optic Nerve Toxicity of Medications." Biomolecules 12, no. 10 (September 29, 2022): 1390. http://dx.doi.org/10.3390/biom12101390.

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Abstract:

It is important for clinicians to consider exposure to toxic substances and nutritional deficiencies when diagnosing and managing cases of vision loss. In these cases, physiologic damage can alter the function of key components of the visual pathway before morphologic changes can be detected by traditional imaging methods. Electrophysiologic tests can aid in the early detection of such functional changes to visual pathway components, including the retina or optic nerve. This review provides an overview of various electrophysiologic techniques, including multifocal electroretinogram (mfERG), full-field ERG (ffERG), electrooculogram (EOG), pattern electroretinogram (PERG), and visual evoked potential (VEP) in monitoring the retinal and optic nerve toxicities of alcohol, amiodarone, cefuroxime, cisplatin, deferoxamine, digoxin, ethambutol, hydroxychloroquine, isotretinoin, ocular siderosis, pentosane, PDE5 inhibitors, phenothiazines (chlorpromazine and thioridazine), quinine, tamoxifen, topiramate, vigabatrin, and vitamin A deficiency.

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Journal articles on the topic 'Functional retinal imaging'

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