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Sousa AI, Marques-Neves C, Vieira PM. Development of a Smartphone-Based System for Intrinsically Photosensitive Retinal Ganglion Cells Targeted Chromatic Pupillometry. Bioengineering (Basel) 2024; 11:267. [PMID: 38534541 DOI: 10.3390/bioengineering11030267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 03/01/2024] [Accepted: 03/04/2024] [Indexed: 03/28/2024] Open
Abstract
Chromatic Pupillometry, used to assess Pupil Light Reflex (PLR) to a coloured light stimulus, has regained interest since the discovery of melanopsin in the intrinsically photosensitive Retinal Ganglion Cells (ipRGCs). This technique has shown the potential to be used as a screening tool for neuro-ophthalmological diseases; however, most of the pupillometers available are expensive and not portable, making it harder for them to be used as a widespread screening tool. In this study, we developed a smartphone-based system for chromatic pupillometry that allows targeted stimulation of the ipRGCs. Using a smartphone, this system is portable and accessible and takes advantage of the location of the ipRGCs in the perifovea. The system incorporates a 3D-printed support for the smartphone and an illumination system. Preliminary tests were carried out on a single individual and then validated on eleven healthy individuals with two different LED intensities. The average Post-Illumination Pupil Light Response 6 s after the stimuli offsets (PIPR-6s) showed a difference between the blue and the red stimuli of 9.5% for both intensities, which aligns with the studies using full-field stimulators. The results validated this system for a targeted stimulation of the ipRGCs for chromatic pupillometry, with the potential to be a portable and accessible screening tool for neuro-ophthalmological diseases.
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Affiliation(s)
- Ana Isabel Sousa
- Department of Physics, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
| | | | - Pedro Manuel Vieira
- Department of Physics, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal
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Romagnoli M, Amore G, Avanzini P, Carelli V, La Morgia C. Chromatic pupillometry for evaluating melanopsin retinal ganglion cell function in Alzheimer's disease and other neurodegenerative disorders: a review. Front Psychol 2024; 14:1295129. [PMID: 38259552 PMCID: PMC10801184 DOI: 10.3389/fpsyg.2023.1295129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 12/11/2023] [Indexed: 01/24/2024] Open
Abstract
The evaluation of pupillary light reflex (PLR) by chromatic pupillometry may provide a unique insight into specific photoreceptor functions. Chromatic pupillometry refers to evaluating PLR to different wavelengths and intensities of light in order to differentiate outer/inner retinal photoreceptor contributions to the PLR. Different protocols have been tested and are now established to assess in-vivo PLR contribution mediated by melanopsin retinal ganglion cells (mRGCs). These intrinsically photosensitive photoreceptors modulate the non-image-forming functions of the eye, which are mainly the circadian photoentrainment and PLR, via projections to the hypothalamic suprachiasmatic and olivary pretectal nucleus, respectively. In this context, chromatic pupillometry has been used as an alternative and non-invasive tool to evaluate the mRGC system in several clinical settings, including hereditary optic neuropathies, glaucoma, and neurodegenerative disorders such as Parkinson's disease (PD), idiopathic/isolated rapid eye movement sleep behavior disorder (iRBD), and Alzheimer's disease (AD). The purpose of this article is to review the key steps of chromatic pupillometry protocols for studying in-vivo mRGC-system functionality and provide the main findings of this technique in the research setting on neurodegeneration. mRGC-dependent pupillary responses are short-wavelength sensitive, have a higher threshold of activation, and are much slower and sustained compared with rod- and cone-mediated responses, driving the tonic component of the PLR during exposure to high-irradiance and continuous light stimulus. Thus, mRGCs contribute mainly to the tonic component of the post-illumination pupil response (PIPR) to bright blue light flash that persists after light stimulation is switched off. Given the role of mRGCs in circadian photoentrainment, the use of chromatic pupillometry to perform a functional evaluation of mRGcs may be proposed as an early biomarker of mRGC-dysfunction in neurodegenerative disorders characterized by circadian and/or sleep dysfunction such as AD, PD, and its prodromal phase iRBD. The evaluation by chromatic pupillometry of mRGC-system functionality may lay the groundwork for a new, easily accessible biomarker that can be exploited also as the starting point for future longitudinal cohort studies aimed at stratifying the risk of conversion in these disorders.
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Affiliation(s)
- Martina Romagnoli
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Giulia Amore
- Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy
| | | | - Valerio Carelli
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
- Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy
| | - Chiara La Morgia
- Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy
- IRCCS Istituto delle Scienze Neurologiche di Bologna, UOC Clinica Neurologica, Bologna, Italy
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Gushi S, Balis V. Mitochondrial Inherited Disorders and their Correlation with Neurodegenerative Diseases. Endocr Metab Immune Disord Drug Targets 2024; 24:381-393. [PMID: 37937560 DOI: 10.2174/0118715303250271231018103202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 07/13/2023] [Accepted: 09/15/2023] [Indexed: 11/09/2023]
Abstract
Mitochondria are essential organelles for the survival of a cell because they produce energy. The cells that need more mitochondria are neurons because they perform a variety of tasks that are necessary to support brain homeostasis. The build-up of abnormal proteins in neurons, as well as their interactions with mitochondrial proteins, or MAM proteins, cause serious health issues. As a result, mitochondrial functions, such as mitophagy, are impaired, resulting in the disorders described in this review. They are also due to mtDNA mutations, which alter the heritability of diseases. The topic of disease prevention, as well as the diagnosis, requires further explanation and exploration. Finally, there are treatments that are quite promising, but more detailed research is needed.
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Affiliation(s)
- Sofjana Gushi
- Department of Health Science and Biomedical Science, Metropolitan College - Thessaloniki Campus, Thessaloniki, Greece
| | - Vasileios Balis
- Department of Health Science and Biomedical Science, Metropolitan College - Thessaloniki Campus, Thessaloniki, Greece
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Ziółkowska N, Lewczuk B, Szyryńska N, Rawicka A, Vyniarska A. Low-Intensity Blue Light Exposure Reduces Melanopsin Expression in Intrinsically Photosensitive Retinal Ganglion Cells and Damages Mitochondria in Retinal Ganglion Cells in Wistar Rats. Cells 2023; 12:cells12071014. [PMID: 37048087 PMCID: PMC10093228 DOI: 10.3390/cells12071014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/18/2023] [Accepted: 03/24/2023] [Indexed: 03/29/2023] Open
Abstract
This study investigated the effect of low-intensity blue light on the albino Wistar rat retina, including intrinsically photosensitive retinal ganglion cells (ipRGCs). Three groups of nine albino Wistar rats were used. One group was continuously exposed to blue light (150 lx) for 2 d (STE); one was exposed to 12 h of blue light and 12 h of darkness for 10 d (LTE); one was maintained in 12 h of white light (150 lx) and 12 h of darkness for 10 d (control). Melanopsin (Opn4) was immunolabelled on retinal whole-mounts. To count and measure Opn4-positive ipRGC somas and dendrites (including Sholl profiles), Neuron J was used. Retinal cryosections were immunolabeled for glial fibrillary acid protein (GFAP) and with terminal deoxynucleotidyl transferase dUTP nick-end labelling for apoptosis detection. LTE reduced the length of Opn4-positive ipRGC dendrites (p = 0.03) and decreased Opn4-immunoreactivity in ipRGC outer stratifying dendrites. LTE and STE decreased the complexity of dendritic arborization (Sholl profile; p < 0.001, p = 0.03, respectively), increased retinal GFAP immunoreactivity (p < 0.001, p = 0.002, respectively), and caused outer segment vesiculation and outer nuclear layer apoptosis. Ultrastructural analysis showed that LTE damaged mitochondria in retinal ganglion cells and in the inner plexiform layer. Thus, LTE to low-intensity blue light harms the retinas of albino Wistar rats.
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Arévalo-López C, Gleitze S, Madariaga S, Plaza-Rosales I. Pupillary response to chromatic light stimuli as a possible biomarker at the early stage of glaucoma: a review. Int Ophthalmol 2023; 43:343-356. [PMID: 35781599 DOI: 10.1007/s10792-022-02381-8] [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: 09/10/2021] [Accepted: 06/14/2022] [Indexed: 02/07/2023]
Abstract
Glaucoma is a multifactorial neurodegenerative disease of the optic nerve currently considered a severe health problem because of its high prevalence, being the primary cause of irreversible blindness worldwide. The most common type corresponds to Primary Open-Angle Glaucoma. Glaucoma produces, among other alterations, a progressive loss of retinal ganglion cells (RGC) and its axons which are the key contributors to generate action potentials that reach the visual cortex to create the visual image. Glaucoma is characterized by Visual Field loss whose main feature is to be painless and therefore makes early detection difficult, causing a late diagnosis and a delayed treatment indication that slows down its progression. Intrinsically photosensitive retinal ganglion cells, which represent a subgroup of RGCs are characterized by their response to short-wave light stimulation close to 480 nm, their non-visual function, and their role in the generation of the pupillary reflex. Currently, the sensitivity of clinical examinations correlates to RGC damage; however, the need for an early damage biomarker is still relevant. It is an urgent task to create new diagnostic approaches to detect an early stage of glaucoma in a prompt, quick, and economical manner. We summarize the pathology of glaucoma and its current clinical detection methods, and we suggest evaluating the pupillary response to chromatic light as a potential biomarker of disease, due to its diagnostic benefit and its cost-effectiveness in clinical practice in order to reduce irreversible damage caused by glaucoma.
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Affiliation(s)
- Carla Arévalo-López
- Department of Medical Technology, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Silvia Gleitze
- Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Samuel Madariaga
- Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Laboratorio de Neurosistemas, Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Ecological Cognitive Neuroscience Group, Santiago, Chile
| | - Iván Plaza-Rosales
- Department of Medical Technology, Faculty of Medicine, Universidad de Chile, Santiago, Chile. .,Biomedical Neuroscience Institute, Faculty of Medicine, Universidad de Chile, Santiago, Chile. .,Laboratorio de Neurosistemas, Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile. .,Ecological Cognitive Neuroscience Group, Santiago, Chile.
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Kim US, Mahroo OA, Mollon JD, Yu-Wai-Man P. Retinal Ganglion Cells-Diversity of Cell Types and Clinical Relevance. Front Neurol 2021; 12:661938. [PMID: 34093409 PMCID: PMC8175861 DOI: 10.3389/fneur.2021.661938] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 04/06/2021] [Indexed: 11/24/2022] Open
Abstract
Retinal ganglion cells (RGCs) are the bridging neurons that connect the retinal input to the visual processing centres within the central nervous system. There is a remarkable diversity of RGCs and the various subtypes have unique morphological features, distinct functions, and characteristic pathways linking the inner retina to the relevant brain areas. A number of psychophysical and electrophysiological tests have been refined to investigate this large and varied population of RGCs. Technological advances, such as high-resolution optical coherence tomography imaging, have provided additional tools to define the pattern of RGC involvement and the chronological sequence of events in both inherited and acquired optic neuropathies. The mechanistic insights gained from these studies, in particular the selective vulnerability and relative resilience of particular RGC subtypes, are of fundamental importance as they are directly relevant to the development of targeted therapies for these invariably progressive blinding diseases. This review provides a comprehensive description of the various types of RGCs, the developments in proposed methods of classification, and the current gaps in our knowledge of how these RGCs are differentially affected depending on the underlying aetiology. The synthesis of the current body of knowledge on the diversity of RGCs and the pathways that are potentially amenable to therapeutic modulation will hopefully lead to much needed effective treatments for patients with optic neuropathies.
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Affiliation(s)
- Ungsoo Samuel Kim
- Kim's Eye Hospital, Seoul, South Korea
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
- Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- *Correspondence: Ungsoo Samuel Kim
| | - Omar A. Mahroo
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
- Section of Ophthalmology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom
| | - John D. Mollon
- Department of Psychology, University of Cambridge, Cambridge, United Kingdom
| | - Patrick Yu-Wai-Man
- John van Geest Centre for Brain Repair and MRC Mitochondrial Biology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
- Cambridge Eye Unit, Addenbrooke's Hospital, Cambridge University Hospitals, Cambridge, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
- Institute of Ophthalmology, University College London, London, United Kingdom
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Chronobiotic effect of melatonin in experimental optic neuritis. Neuropharmacology 2020; 182:108401. [PMID: 33197466 DOI: 10.1016/j.neuropharm.2020.108401] [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: 07/17/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 11/23/2022]
Abstract
Optic neuritis (ON) is an inflammatory condition of the optic nerve, which leads to retinal ganglion cell (RGC) loss. A subset of RGCs expressing the photopigment melanopsin regulates non-image-forming visual system (NIFVS) functions such as pupillary light reflex (PLR) and circadian rhythms. Melatonin is a chronobiotic agent able to regulate the circadian system. We analyzed the effect of ON on the NIFVS, and the effect of melatonin on the NIFVS alterations induced by ON. For this purpose, optic nerves from male Wistar rats received vehicle or bacterial lipopolysaccharide (LPS), and one group of animals received a subcutaneous pellet of melatonin or a sham procedure. The NIFVS was analyzed in terms of: i) blue light-evoked PLR, ii) the communication between the retina and the suprachiasmatic nuclei (by anterograde transport, and ex vivo magnetic resonance images), iii) locomotor activity rhythm, and iv) Brn3a(+) and melanopsin(+) RGC number (by immunohistochemistry). Experimental ON significantly decreased the blue light-evoked PLR, induced a misconnection between the retina and the suprachiasmatic nuclei, decreased Brn3a(+) RGCs, but not melanopsin(+) RGC number. A bilateral injection of LPS significantly increased the light (but not dark) phase locomotor activity, rhythm periodicity, and time of offset activity. Melatonin prevented the decrease in blue light-evoked PLR, and locomotor activity rhythm alterations induced by ON. These results support that ON provoked alterations of the circadian physiology, and that melatonin could restore the circadian system misalignment.
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Ba-Ali S, Brøndsted AE, Andersen HU, Jennum P, Lund-Andersen H. Pupillary light responses in type 1 and type 2 diabetics with and without retinopathy. Acta Ophthalmol 2020; 98:477-484. [PMID: 31943805 DOI: 10.1111/aos.14348] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 12/20/2019] [Indexed: 01/14/2023]
Abstract
OBJECTIVE We assessed the function of rod/cones and melanopsin in type 1 (T1DM) and type 2 diabetes mellitus (T2DM) with and without non-proliferative diabetic retinopathy (NPDR). METHODS We performed pupillometry on 22 healthy controls and four diabetic groups: 12 T1DM patients without NPDR and 12 with moderate NPDR, and 16 T2DM patients without NPDR and 12 with moderate NPDR. Monocular stimulations of 20 seconds with red (λ = 633 nm) and blue light (λ = 463 nm) at ~15 log quanta/cm2 /second were performed. The primary outcome was the melanopsin-mediated late redilation phase of postillumination pupillary light response (PIPRL ate ) to blue light. The secondary outcomes were the mixed rod/cone and melanopsin responses, that is maximal pupil constriction and the early redilation phase of PIPR (PIPRE arly ). RESULTS Late redilation phase of PIPR (PIPRL ate ) to blue and red light stimuli was not significantly different between healthy control and the four diabetic groups (n.s.). The maximal pupil contractions to blue light stimulus were significantly reduced in T1DM patients as well as in T2DM patients with NPDR (p ≤ 0.02), whereas for red light stimuli, the maximal pupil constriction was only reduced in T2DM with NPDR (p < 0.01). Early redilation phase of PIPR (PIPRE arly ) to blue and red light stimuli was not significantly different between healthy controls and diabetic patients (n.s.). CONCLUSION Neither the PIPRE arly nor the PIPRL ate was significantly reduced in diabetics with or without NPDR compared to healthy controls. The reduced maximal pupil constrictions in diabetics with NPDR indicate decreased mixed rod/cone and melanopsin responses.
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Affiliation(s)
- Shakoor Ba-Ali
- Department of Ophthalmology, Rigshospitalet, Glostrup, Denmark.,Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Poul Jennum
- Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Danish Centre for Sleep Medicine, Neurophysiology Clinic, Rigshospitalet, Glostrup, Denmark
| | - Henrik Lund-Andersen
- Department of Ophthalmology, Rigshospitalet, Glostrup, Denmark.,Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Steno Diabetes Centre, Gentofte, Denmark
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Kelbsch C, Strasser T, Chen Y, Feigl B, Gamlin PD, Kardon R, Peters T, Roecklein KA, Steinhauer SR, Szabadi E, Zele AJ, Wilhelm H, Wilhelm BJ. Standards in Pupillography. Front Neurol 2019; 10:129. [PMID: 30853933 PMCID: PMC6395400 DOI: 10.3389/fneur.2019.00129] [Citation(s) in RCA: 100] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 01/31/2019] [Indexed: 12/31/2022] Open
Abstract
The number of research groups studying the pupil is increasing, as is the number of publications. Consequently, new standards in pupillography are needed to formalize the methodology including recording conditions, stimulus characteristics, as well as suitable parameters of evaluation. Since the description of intrinsically photosensitive retinal ganglion cells (ipRGCs) there has been an increased interest and broader application of pupillography in ophthalmology as well as other fields including psychology and chronobiology. Color pupillography plays an important role not only in research but also in clinical observational and therapy studies like gene therapy of hereditary retinal degenerations and psychopathology. Stimuli can vary in size, brightness, duration, and wavelength. Stimulus paradigms determine whether rhodopsin-driven rod responses, opsin-driven cone responses, or melanopsin-driven ipRGC responses are primarily elicited. Background illumination, adaptation state, and instruction for the participants will furthermore influence the results. This standard recommends a minimum set of variables to be used for pupillography and specified in the publication methodologies. Initiated at the 32nd International Pupil Colloquium 2017 in Morges, Switzerland, the aim of this manuscript is to outline standards in pupillography based on current knowledge and experience of pupil experts in order to achieve greater comparability of pupillographic studies. Such standards will particularly facilitate the proper application of pupillography by researchers new to the field. First we describe general standards, followed by specific suggestions concerning the demands of different targets of pupil research: the afferent and efferent reflex arc, pharmacology, psychology, sleepiness-related research and animal studies.
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Affiliation(s)
- Carina Kelbsch
- Pupil Research Group, Centre for Ophthalmology, University Hospitals Tübingen, Tübingen, Germany
| | - Torsten Strasser
- Pupil Research Group, Centre for Ophthalmology, University Hospitals Tübingen, Tübingen, Germany
| | - Yanjun Chen
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, AL, United States
| | - Beatrix Feigl
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia
- School of Biomedical Sciences, Queensland University of Technology, Brisbane, QLD, Australia
- Queensland Eye Institute, Brisbane, QLD, Australia
| | - Paul D. Gamlin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Randy Kardon
- Neuro-Ophthalmology Division, University of Iowa and Iowa City VA Healthcare System, Iowa City, LA, United States
| | - Tobias Peters
- Pupil Research Group, Centre for Ophthalmology, University Hospitals Tübingen, Tübingen, Germany
| | - Kathryn A. Roecklein
- Department of Psychology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Stuart R. Steinhauer
- VA Pittsburgh Healthcare System, VISN 4 MIRECC, University Drive C, Pittsburgh, PA, United States
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Elemer Szabadi
- Developmental Psychiatry, University of Nottingham, Nottingham, United Kingdom
| | - Andrew J. Zele
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia
- School of Optometry and Vision Science, Queensland University of Technology, Brisbane, QLD, Australia
| | - Helmut Wilhelm
- Pupil Research Group, Centre for Ophthalmology, University Hospitals Tübingen, Tübingen, Germany
| | - Barbara J. Wilhelm
- Pupil Research Group, Centre for Ophthalmology, University Hospitals Tübingen, Tübingen, Germany
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Rukmini AV, Milea D, Gooley JJ. Chromatic Pupillometry Methods for Assessing Photoreceptor Health in Retinal and Optic Nerve Diseases. Front Neurol 2019; 10:76. [PMID: 30809186 PMCID: PMC6379484 DOI: 10.3389/fneur.2019.00076] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 01/21/2019] [Indexed: 12/19/2022] Open
Abstract
The pupillary light reflex is mediated by melanopsin-containing intrinsically-photosensitive retinal ganglion cells (ipRGCs), which also receive input from rods and cones. Melanopsin-dependent pupillary light responses are short-wavelength sensitive, have a higher threshold of activation, and are much slower to activate and de-activate compared with rod/cone-mediated responses. Given that rod/cone photoreceptors and melanopsin differ in their response properties, light stimuli can be designed to stimulate preferentially each of the different photoreceptor types, providing a read-out of their function. This has given rise to chromatic pupillometry methods that aim to assess the health of outer retinal photoreceptors and ipRGCs by measuring pupillary responses to blue or red light stimuli. Here, we review different types of chromatic pupillometry protocols that have been tested in patients with retinal or optic nerve disease, including approaches that use short-duration light exposures or continuous exposure to light. Across different protocols, patients with outer retinal disease (e.g., retinitis pigmentosa or Leber congenital amaurosis) show reduced or absent pupillary responses to dim blue-light stimuli used to assess rod function, and reduced responses to moderately-bright red-light stimuli used to assess cone function. By comparison, patients with optic nerve disease (e.g., glaucoma or ischemic optic neuropathy, but not mitochondrial disease) show impaired pupillary responses during continuous exposure to bright blue-light stimuli, and a reduced post-illumination pupillary response after light offset, used to assess melanopsin function. These proof-of-concept studies demonstrate that chromatic pupillometry methods can be used to assess damage to rod/cone photoreceptors and ipRGCs. In future studies, it will be important to determine whether chromatic pupillometry methods can be used for screening and early detection of retinal and optic nerve diseases. Such methods may also prove useful for objectively evaluating the degree of recovery to ipRGC function in blind patients who undergo gene therapy or other treatments to restore vision.
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Affiliation(s)
- A V Rukmini
- Programme in Neuroscience and Behavioural Disorders, Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore, Singapore
| | - Dan Milea
- Singapore National Eye Centre, Singapore Eye Research Institute, Singapore, Singapore.,The Ophthalmology and Visual Sciences Academic Clinical Programme (EYE-ACP), SingHealth and Duke-NUS, Singapore, Singapore
| | - Joshua J Gooley
- Programme in Neuroscience and Behavioural Disorders, Centre for Cognitive Neuroscience, Duke-NUS Medical School, Singapore, Singapore
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Affiliation(s)
- M Kolko
- Department of Drug Design and Pharmacology, Jagtvej 160, Building 22, 2100 Copenhagen O, Denmark; Zealand University Hospital, Department of Ophthalmology, 4000 Roskilde, Denmark.
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