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Chiaravalli G, Ravasenga T, Colombo E, Jasnoor, Francia S, Di Marco S, Sacco R, Pertile G, Benfenati F, Lanzani G. The light-dependent pseudo-capacitive charging of conjugated polymer nanoparticles coupled with the depolarization of the neuronal membrane. Phys Chem Chem Phys 2023; 26:47-56. [PMID: 38054374 DOI: 10.1039/d3cp04386j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
The mechanism underlying visual restoration in blind animal models of retinitis pigmentosa using a liquid retina prosthesis based on semiconductive polymeric nanoparticles is still being debated. Through the application of mathematical models and specific experiments, we developed a coherent understanding of abiotic/biotic coupling, capturing the essential mechanism of photostimulation responsible for nanoparticle-induced retina activation. Our modeling is based on the solution of drift-diffusion and Poisson-Nernst-Planck models in the multi-physics neuron-cleft-nanoparticle-extracellular space domain, accounting for the electro-chemical motion of all the relevant species following photoexcitation. Modeling was coupled with electron microscopy to estimate the size of the neuron-nanoparticle cleft and electrophysiology on retina explants acutely or chronically injected with nanoparticles. Overall, we present a consistent picture of electrostatic depolarization of the bipolar cell driven by the pseudo-capacitive charging of the nanoparticle. We demonstrate that the highly resistive cleft composition, due to filling by adhesion/extracellular matrix proteins, is a crucial ingredient for establishing functional electrostatic coupling. Additionally, we show that the photo-chemical generation of reactive oxygen species (ROS) becomes relevant only at very high light intensities, far exceeding the physiological ones, in agreement with the lack of phototoxicity shown in vivo.
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Affiliation(s)
- Greta Chiaravalli
- Center for Nano Science Technology, Istituto Italiano di Tecnologia, Milano, Italy.
- Politecnico di Milano, Physics Department, Milano, Italy
| | - Tiziana Ravasenga
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.
- IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Elisabetta Colombo
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.
- IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Jasnoor
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.
- Department of Experimental Medicine, University of Genova, Genova, Italy
| | - Simona Francia
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.
- IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Stefano Di Marco
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.
- IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Riccardo Sacco
- Politecnico di Milano, Mathematics Department, Milano, Italy
| | - Grazia Pertile
- Department of Ophthalmology, IRCCS Sacrocuore Don Calabria Hospital, Negrar, Verona, Italy
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy.
- IRCCS Ospedale Policlinico San Martino, Genova, Italy
| | - Guglielmo Lanzani
- Center for Nano Science Technology, Istituto Italiano di Tecnologia, Milano, Italy.
- Politecnico di Milano, Physics Department, Milano, Italy
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Gupta P, Murray JM, Beylergil SB, Jacobs J, Kilbane CW, Shaikh AG, Ghasia FF. Objective assessment of eye alignment and disparity-driven vergence in Parkinson's disease. Front Aging Neurosci 2023; 15:1217765. [PMID: 38020777 PMCID: PMC10643751 DOI: 10.3389/fnagi.2023.1217765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 10/05/2023] [Indexed: 12/01/2023] Open
Abstract
Background Self-reported diplopia is described in up to one-third of Parkinson's disease (PD) patients. Objective The purpose of our study was to expand our understanding of the mechanistic underpinnings of diplopia in PD. We hypothesize that the time-based control of eye alignment and increased eye deviation under binocular viewing will be related to the fusion-initiating and fusion-maintaining component deficits of disparity-driven vergence in PD. Methods We used high-resolution video-oculography to measure eye alignment under binocular and monocular viewing and disparity-driven vergence in 33 PD and 10 age-matched healthy participants. We computed eye deviation and time-based control of eye alignment, occurrence of conjugate saccadic eye movements, latency and gain of vergence (fusion initiation), and variance of eye position at the end of dynamic vergence (fusion maintenance). Results We categorized PD subjects into three groups, considering their time-based control of eye alignment as compared to healthy controls in binocular viewing. Group 1 = 45% had good control and spent >80% of the time when the eyes were well-aligned, Group 2 = 26% had intermediate control and spent <80% but greater >5% of the time when the eyes were well-aligned, and Group 3 = 29% had very poor control with increased eye deviation majority of the times (<5% of the time when the eyes were well-aligned). All three groups exhibited greater eye deviation under monocular viewing than controls. PD subjects exhibited fusion-initiating and fusion-maintaining vergence deficits (prolonged latencies, reduced vergence gain, increased variance of fusion-maintaining component) with a greater probability of saccadic movements than controls. Group 2 and Group 3 subjects were more likely to exhibit failure to initiate vergence (>20%) than Group 1 (13%) and controls (0%) trials. No significant difference was found in the Unified Parkinson's Disease Rating Scale (UPDRS-a tool to measure the severity of PD) values between the three PD groups (Group 1 = 33.69 ± 14.22, Group 2 = 38.43 ± 22.61, and Group 3 = 23.44 ± 1, p > 0.05). Conclusion The majority of PD subjects within our cohort had binocular dysfunction with increased eye deviation under monocular viewing and disparity-driven vergence deficits. PD subjects with intermediate or poor control of eye deviation under binocular viewing had greater fusion-initiating and fusion-maintaining vergence deficits. The study highlights the importance of assessing binocular dysfunction in PD subjects independent of the severity of motor symptoms.
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Affiliation(s)
- Palak Gupta
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
- Visual Neurosciences and Ocular Motility Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
- Daroff-Dell’Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, OH, United States
| | - Jordan M. Murray
- Visual Neurosciences and Ocular Motility Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Sinem Balta Beylergil
- Daroff-Dell’Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, OH, United States
| | - Jonathan Jacobs
- Daroff-Dell’Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, OH, United States
| | - Camilla W. Kilbane
- Department of Neurology, University Hospitals, Cleveland, OH, United States
| | - Aasef G. Shaikh
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
- Daroff-Dell’Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, OH, United States
- Department of Neurology, University Hospitals, Cleveland, OH, United States
- Neurology Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States
| | - Fatema F. Ghasia
- Visual Neurosciences and Ocular Motility Laboratory, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
- Daroff-Dell’Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, OH, United States
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Dulaney CS, Murray J, Ghasia F. Contrast sensitivity, optotype acuity and fixation eye movement abnormalities in amblyopia under binocular viewing. J Neurol Sci 2023; 451:120721. [PMID: 37433244 DOI: 10.1016/j.jns.2023.120721] [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: 07/20/2022] [Revised: 06/20/2023] [Accepted: 06/24/2023] [Indexed: 07/13/2023]
Abstract
INTRODUCTION Visual function deficits are seen in amblyopic subjects during fellow and binocular viewing. The purpose of the study was to examine the relationship between Fixation Eye Movement (FEM) abnormalities and binocular contrast sensitivity and optotype acuity deficits in amblyopia. METHODS We recruited 10 controls and 25 amblyopic subjects [Anisometropic = 6, Strabismic = 10, Mixed = 9]. We measured binocular contrast sensitivity at spatial frequencies 1,2, 4, 8, 12 and 16 and binocular and monocular optotype acuity using a staircase procedure. We recorded FEMs using high-resolution video-oculography and classified subjects as having no nystagmus(None = 9) or nystagmus without FMN(n = 7) and with Fusion Maldevelopment Nystagmus (FMN)(n = 9). We computed the fixation instability, amplitude and velocity of the fast and slow FEMs. RESULTS Amblyopic subjects with and without nystagmus had worse binocular contrast sensitivity at spatial frequencies 12 and 16 and binocular optotype acuity than controls. The abnormalities were most pronounced in amblyopic subjects with FMN. Fixation instability of the Fellow Eye and Amblyopic Eye and vergence instability, amplitude of fast FEMs and velocity of slow FEMs were increased with reduced binocular contrast sensitivity and reduced optotype acuity in amblyopic subjects. CONCLUSIONS Fixation instability of Fellow Eye and Amblyopic Eye, optotype acuity and contrast sensitivity deficits are seen under binocular viewing in amblyopic subjects with and without nystagmus but are most pronounced in those with FMN. FEMs abnormalities correlate with both lower order (contrast sensitivity) and higher order (optotype acuity) visual function impairment in amblyopia.
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Affiliation(s)
- Cody S Dulaney
- Cleveland Clinic Cole Eye Institute, Visual Neurosciences and Ocular Motility Laboratory, Cleveland, OH, USA
| | - Jordan Murray
- Cleveland Clinic Cole Eye Institute, Visual Neurosciences and Ocular Motility Laboratory, Cleveland, OH, USA
| | - Fatema Ghasia
- Cleveland Clinic Cole Eye Institute, Visual Neurosciences and Ocular Motility Laboratory, Cleveland, OH, USA.
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Raveendran RN, Krishnan AK, Thompson B. Reduced fixation stability induced by peripheral viewing does not contribute to crowding. J Vis 2020; 20:3. [PMID: 33007078 PMCID: PMC7545060 DOI: 10.1167/jov.20.10.3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Attending to peripheral visual targets while maintaining central fixation, a process that involves covert attention, reduces fixation stability. Here, we tested the hypothesis that changes in fixation stability induced by peripheral viewing contribute to crowding in peripheral vision by increasing positional uncertainty. We first assessed whether fixation was less stable during peripheral versus central (foveal) viewing for both crowded and uncrowded stimuli. We then tested whether fixation stability during peripheral viewing was associated with the extent of crowding. Fourteen participants performed a tumbling E orientation discrimination task at three different eccentricities (0°, 5°, 10°). The target was presented with or without flankers. Fixational eye movements were measured using an infrared video-based eyetracker. A central fixation cross was provided for the two peripheral viewing conditions, and optotype size was scaled for each eccentricity. Discrimination of appropriately scaled uncrowded stimuli was unaffected by eccentricity, whereas discrimination of crowded stimuli deteriorated dramatically with eccentricity, despite scaling. Both crowded and uncrowded peripheral stimuli were associated with reduced fixation stability, increased microsaccadic amplitude, and a greater proportion of horizontal microsaccades relative to centrally presented stimuli. However, these effects were not associated with the magnitude of crowding. This suggests that reduced fixation stability due to peripheral viewing does not contribute to crowding in peripheral vision.
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Affiliation(s)
- Rajkumar Nallour Raveendran
- Envision Research Institute, Wichita, KS, USA.,School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, Canada.,
| | | | - Benjamin Thompson
- School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, Canada.,Centre for Eye and Vision Research, Hong Kong.,
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Tang S, Skelly P, Otero-Millan J, Jacobs J, Murray J, Shaikh AG, Ghasia FF. Effects of visual blur on microsaccades during visual exploration. J Eye Mov Res 2019; 12. [PMID: 33828759 PMCID: PMC7962686 DOI: 10.16910/jemr.12.6.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Microsaccades shift the image on the fovea and counteract visual fading. They also serve as an optimal
sampling strategy while viewing complex visual scenes. Microsaccade production relies on the amount of
retinal error or acuity demand of a visual task. The goal of this study was to assess the effects of blur induced by uncorrected refractive error on visual search. Eye movements were recorded in fourteen healthy
subjects with uncorrected and corrected refractive error while they performed a) visual fixation b) blankscene viewing c) visual search (spot the difference) tasks. Microsaccades, saccades, correctly identified
differences and reaction times were analyzed. The frequency of microsaccades and correctly identified
differences were lower in the uncorrected refractive error during visual search. No similar change in microsaccades was seen during blank-scene viewing and gaze holding tasks. These findings suggest that visual
blur, hence the precision of an image on the fovea, has an important role in calibrating the amplitude of
microsaccades during visual scanning.
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Affiliation(s)
- Sherry Tang
- Case Western Reserve University School of Medicine, USA
| | | | - Jorge Otero-Millan
- Vestibular and Ocular Motor Research Laboratory, Johns Hopkins University, USA
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Chen D, Otero-Millan J, Kumar P, Shaikh AG, Ghasia FF. Visual Search in Amblyopia: Abnormal Fixational Eye Movements and Suboptimal Sampling Strategies. Invest Ophthalmol Vis Sci 2019; 59:4506-4517. [PMID: 30208418 DOI: 10.1167/iovs.18-24794] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Microsaccades shift the image on the fovea and counteract visual fading. They are also thought to serve as an optimal sampling strategy while viewing complex visual scenes. The goal of our study was to assess visual search in amblyopic children. Methods Twenty-one amblyopic children with varying severity of amblyopia and 10 healthy controls were recruited. Eye movements were recorded using infrared video-oculography during amblyopic and fellow eye viewing while the subjects performed (1) visual fixation, (2) exploration of a blank scene, and (3) visual search task (spot the difference between two images). The number of correctly identified picture differences and reaction time were recorded. Microsaccade, saccades, and intersaccadic drifts were analyzed in patients without latent nystagmus (LN). Slow phase velocities were computed for patients with LN. Results Both patients with and without LN were able to spot the same number of differences but took longer during fellow eye viewing compared to controls. The ability to identify differences was diminished during amblyopic eye viewing particularly those with LN and severe amblyopia. We found reduced frequencies of microsaccades and saccades in both amblyopic and fellow eyes during fixation and visual search but not during exploration of blank scene. Across all tasks, amblyopes with LN had increased intersaccadic drifts. Conclusions Our findings suggest that deficient microsaccade and saccadic activity contributes to poorer sampling strategy in amblyopia, which is seen in both amblyopic and fellow eye. These deficits are more notable among subjects who experienced binocular decorrelation earlier in life, with subsequent development of LN.
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Affiliation(s)
- Dinah Chen
- Department of Ophthalmology, New York University School of Medicine, New York, New York, United States.,Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Jorge Otero-Millan
- Department of Neurology, Johns Hopkins University, Baltimore, Maryland, United States
| | - Priyanka Kumar
- Department of Ophthalmology, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States
| | - Aasef G Shaikh
- Department of Neurology, University Hospitals, Case Western Reserve University, Cleveland, Ohio, United States.,Daroff-Dell'Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, Ohio, United States
| | - Fatema F Ghasia
- Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States.,Daroff-Dell'Osso Ocular Motility Laboratory, Cleveland VA Medical Center, Cleveland, Ohio, United States
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Shaikh AG, Ghasia FF. Saccades in Parkinson's disease: Hypometric, slow, and maladaptive. PROGRESS IN BRAIN RESEARCH 2019; 249:81-94. [DOI: 10.1016/bs.pbr.2019.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Paraneoplastic seesaw nystagmus and opsoclonus provides evidence for hyperexcitable reciprocally innervating mesencephalic network. J Neurol Sci 2018; 390:239-245. [DOI: 10.1016/j.jns.2018.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/28/2018] [Accepted: 05/01/2018] [Indexed: 11/18/2022]
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Shaikh AG, Finkelstein SR, Schuchard R, Ross G, Juncos JL. Fixational eye movements in Tourette syndrome. Neurol Sci 2017; 38:1977-1984. [PMID: 28815321 DOI: 10.1007/s10072-017-3069-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Accepted: 07/11/2017] [Indexed: 10/19/2022]
Abstract
Studies of saccadic eye movements in subjects with Tourette syndrome (TS) have provided additional evidence that there is a link between TS symptoms and deficits in fronto-striato-thalamic networks. These studies revealed impaired timing and inhibition of saccades. We compared fixational eye movements, such as microsaccades and ocular drifts, in subjects with TS and healthy controls.We measured horizontal and vertical eye positions with video-oculography in 14 subjects with Tourette syndrome. We found reduced microsaccade amplitude but increased time between adjacent microsaccades (intersaccadic interval). Hence, the rate of microsaccades was reduced in subjects with TS compared to controls. Measure of ocular stability during intersaccadic intervals revealed increased drift velocity and increased variance in eye position. We hypothesize that increased activity of the direct fronto-striatal pathway and the resulting reduction in basal ganglia outflow targeting the superior colliculus fixation zone affect the rate and amplitude of microsaccades in subjects with TS. The resulting impairment in frontal eye field fixation leads to increased drifts during intersaccadic interval in subjects with TS. Possible clinical implication for these results is that fixational eye movements can be objective biological markers of TS.
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Affiliation(s)
- Aasef G Shaikh
- Depatment of Neurology, Case Western Reserve University, Cleveland, OH, USA. .,Daroff-DelOsso Ocular Motility Laboratory and Neurology Service, Louis Stokes VA Medical Center, Cleveland, OH, USA. .,Department of Neurology, University Hospitals Case Medical Center, 11100 Euclid Avenue, Cleveland, OH, 44110, USA.
| | | | - Ronald Schuchard
- Department of Neurosurgery, Stanford University, Stanford, CA, USA
| | | | - Jorge L Juncos
- Depatment of Neurology, Emory University, Atlanta, GA, USA
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