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Jiang X, Bhatti T, Tariq A, Leo SM, Aychoua N, Webster AR, Hysi PG, Hammond CJ, Mahroo OA. Cone-driven strong flash electroretinograms in healthy adults: Prevalence of negative waveforms. Doc Ophthalmol 2024; 148:25-36. [PMID: 37924416 PMCID: PMC10879345 DOI: 10.1007/s10633-023-09957-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 10/05/2023] [Indexed: 11/06/2023]
Abstract
PURPOSE Both rod and cone-driven signals contribute to the electroretinogram (ERG) elicited by a standard strong flash in the dark. Negative ERGs usually reflect inner retinal dysfunction. However, in diseases where rod photoreceptor function is selectively lost, a negative waveform might represent the response of the dark-adapted cone system. To investigate the dark-adapted cone-driven waveform in healthy individuals, we delivered flashes on a dim blue background, designed to saturate the rods, but minimally adapt the cones. METHODS ERGs were recorded, using conductive fibre electrodes, in adults from the TwinsUK cohort. Responses to 13 cd m-2 s white xenon flashes (similar to the standard DA 10 flash), delivered on a blue background, were analysed. Photopic and scotopic strengths of the background were 1.3 and 30 cd m-2, respectively; through a dilated pupil, this is expected to largely saturate the rods, but adapt the cones much less than the standard ISCEV background. RESULTS Mean (SD) participant age was 62.5 (11.3) years (93% female). ERGs from 203 right and 204 left eyes were included, with mean (SD) b/a ratios of 1.22 (0.28) and 1.18 (0.28), respectively (medians, 1.19 and 1.17). Proportions with negative waveforms were 23 and 26%, respectively. Right and left eye b/a ratios were strongly correlated (correlation coefficient 0.74, p < 0.0001). We found no significant correlation of b/a ratio with age. CONCLUSIONS Over 20% of eyes showed b/a ratios less than 1, consistent with the notion that dark-adapted cone-driven responses to standard bright flashes can have negative waveforms. The majority had ratios greater than 1. Thus, whilst selective loss of rod function can yield a negative waveform (with reduced a-wave) in some, our findings also suggest that loss of rod function can occur without necessarily yielding a negative ERG. One potential limitation is possible mild cone system adaptation by the background.
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Affiliation(s)
- Xiaofan Jiang
- Institute of Ophthalmology, University College London, Bath Street, London, UK
- Department of Ophthalmology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
- Department of Twin Research and Genetic Epidemiology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
| | - Taha Bhatti
- Department of Ophthalmology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
- Department of Twin Research and Genetic Epidemiology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
| | - Ambreen Tariq
- Department of Ophthalmology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
- Department of Twin Research and Genetic Epidemiology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
| | - Shaun M Leo
- NIHR Biomedical Research Centre at Moorfields Eye Hospital and the UCL Institute of Ophthalmology, 162 City Road, London, UK
| | - Nancy Aychoua
- Institute of Ophthalmology, University College London, Bath Street, London, UK
- NIHR Biomedical Research Centre at Moorfields Eye Hospital and the UCL Institute of Ophthalmology, 162 City Road, London, UK
| | - Andrew R Webster
- Institute of Ophthalmology, University College London, Bath Street, London, UK
- NIHR Biomedical Research Centre at Moorfields Eye Hospital and the UCL Institute of Ophthalmology, 162 City Road, London, UK
| | - Pirro G Hysi
- Department of Ophthalmology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
- Department of Twin Research and Genetic Epidemiology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
| | - Christopher J Hammond
- Department of Ophthalmology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
- Department of Twin Research and Genetic Epidemiology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK
| | - Omar A Mahroo
- Institute of Ophthalmology, University College London, Bath Street, London, UK.
- Department of Ophthalmology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK.
- Department of Twin Research and Genetic Epidemiology, King's College London, St Thomas' Hospital Campus, Westminster Bridge Road, London, UK.
- NIHR Biomedical Research Centre at Moorfields Eye Hospital and the UCL Institute of Ophthalmology, 162 City Road, London, UK.
- Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
- Department of Translational Ophthalmology, Wills Eye Hospital, Philadelphia, PA, USA.
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Baer SM, Chang S, Crook SM, Gardner CL, Jones JR, Ringhofer C, Nelson RF. A multiscale continuum model of the vertebrate outer retina: The temporal dynamics of background-induced flicker enhancement. J Theor Biol 2021; 525:110763. [PMID: 34000285 DOI: 10.1016/j.jtbi.2021.110763] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Revised: 04/28/2021] [Accepted: 05/07/2021] [Indexed: 11/25/2022]
Abstract
The retina is a part of the central nervous system that is accessible, well documented, and studied by researchers spanning the clinical, experimental, and theoretical sciences. Here, we mathematically model the subcircuits of the outer plexiform layer of the retina on two spatial scales: that of an individual synapse and that of the scale of the receptive field (hundreds to thousands of synapses). To this end we formulate a continuum spine model (a partial differential equation system) that incorporates the horizontal cell syncytium and its numerous processes (spines) within cone pedicles. With this multiscale modeling approach, detailed biophysical mechanisms at the synaptic level are retained while scaling up to the receptive field level. As an example of its utility, the model is applied to study background-induced flicker enhancement in which the onset of a dim background enhances the center flicker response of horizontal cells. Simulation results, in comparison with flicker enhancement data for square, slit, and disk test regions, suggest that feedback mechanisms that are voltage-axis modulators of cone calcium channels (for example, ephaptic and/or pH feedback) are robust in capturing the temporal dynamics of background-induced flicker enhancement. The value and potential of this continuum spine approach is that it provides a framework for mathematically modeling the input-output properties of the entire receptive field of the outer retina while implementing the latest models for transmission mechanisms at the synaptic level.
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Affiliation(s)
- Steven M Baer
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, United States.
| | - Shaojie Chang
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, United States; The High School Affiliated to Beijing Normal University, Beijing 100052, PR China
| | - Sharon M Crook
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, United States
| | - Carl L Gardner
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, United States
| | - Jeremiah R Jones
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, United States
| | - Christian Ringhofer
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ 85287, United States
| | - Ralph F Nelson
- Neural Circuits Unit, Basic Neuroscience Program, NINDS, NIH, Bethesda, MD 20892, United States
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