The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Agnes M F Wong - One of the best experts on this subject based on the ideXlab platform.
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investigation of light induced Lacrimation and pupillary responses in episodic migraine
PLOS ONE, 2020Co-Authors: Marija Zivcevska, Shaobo Lei, Alan Blakeman, Daune Macgregor, Herbert C Goltz, Agnes M F WongAbstract:The purpose of this pilot study was to investigate the light-induced pupillary and Lacrimation responses mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) in migraine. Ten participants with episodic migraine and normal tear production, as well as eleven visually normal controls participated in this study. Following an initial baseline trial (no light flash), participants received seven incremental and alternating red and blue light flashes. Pupillometry recording of the left eye and a 1-min anesthetized Schirmer's test of the right eye (using 0.5% proparacaine) were performed simultaneously. Intrinsic and extrinsic ipRGC photoactivities did not differ between migraine participants and controls across all intensities and wavelengths. Migraine participants, however, had significantly lower Lacrimation than controls following the highest blue intensity. A positive correlation was found between melanopsin-driven post-illumination pupillary responses and Lacrimation following blue stimulation in both groups. Our results show that participants with self-reported photophobia have normal ipRGC-driven responses, suggesting that photophobia and pupillary function may be mediated by distinct ipRGC circuits. The positive correlation between melanopsin-driven pupillary responses and light-induced Lacrimation suggests the afferent arm of the light-induced Lacrimation reflex is melanopsin-mediated and functions normally in migraine. Lastly, the reduced melanopsin-mediated Lacrimation at the highest stimulus suggests the efferent arm of the Lacrimation reflex is attenuated under certain conditions, which may be a harbinger of dry eye in migraine.
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the relation between light induced Lacrimation and the melanopsin driven postillumination pupil response
Investigative Ophthalmology & Visual Science, 2017Co-Authors: Shaobo Lei, Marija Zivcevska, Herbert C Goltz, Xingqiao Chen, Agnes M F WongAbstract:Purpose To investigate the chromatic characteristics and intensity-response function of light-induced reflex Lacrimation and its correlation with the melanopsin-driven postillumination pupil response (PIPR). Methods Eleven visually normal participants completed the experiment. Lacrimation was measured in one eye by placing a calibrated filter paper strip in the conjunctival sac over a 1 minute-interval (Schirmer's test) during which participants received either no light stimulation (baseline trial) or one flash of blue or red light stimuli presented binocularly with a Ganzfeld stimulator, while the pupil response was recorded simultaneously from the fellow eye by using an eye tracker. Light stimulation trials were presented in alternating fashion at seven incremental intensity steps (0.1, 1, 3.16, 10, 31.6, 100, and 400 cd/m2). Postillumination pupil response was defined as the mean pupil constriction from 10 to 30 seconds post illumination. Results The amount of Lacrimation in response to 10 to 400 cd/m2 blue light was significantly greater than baseline and increased monotonically with increasing light intensity. Red light did not induce significant reflex Lacrimation until the brightest stimulation at 400 cd/m2. There was a positive linear correlation between PIPR and Lacrimation in response to blue light (r = 0.74, P < 0.001) but not to red light (r = 0.13, P = 0.25). Conclusions The chromatic characteristics and intensity-response of light-induced Lacrimation are highly consistent with the features of melanopsin phototransduction. This finding is the first in vivo evidence in humans, supporting the hypothesis that light-induced reflex Lacrimation is mediated primarily by melanopsin photoactivity, and provides new insight into the putative mechanisms of photophobia.
Ian D Meng - One of the best experts on this subject based on the ideXlab platform.
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the role of corneal afferent neurons in regulating tears under normal and dry eye conditions
Experimental Eye Research, 2013Co-Authors: Ian D Meng, Masayuki KuroseAbstract:The cornea is one of several orofacial structures requiring glandular secretion for proper lubrication. Glandular secretion is regulated through a neural reflex initiated by trigeminal primary afferent neurons innervating the corneal epithelium. Corneal sensory afferents must respond to irritating and potentially damaging stimuli, as well as drying that occurs with evaporation of the tear film, and the physiological properties of corneal afferents are consistent with these requirements. Polymodal neurons are sensitive to noxious mechanical, thermal and chemical stimuli, mechanoreceptive neurons are selectively activated by mechanical stimuli, and cool cells respond to innocuous cooling. The central terminations of corneal primary afferents are located within two regions of the spinal trigeminal nucleus. The more rostral region, located at the transition between the trigeminal subnucleus caudalis and interpolaris, represents a critical relay for the regulation of the Lacrimation reflex. From this region, major control of Lacrimation is carried through projections to preganglionic parasympathetic neurons located in or around the superior salivatory nucleus. Dry eye syndrome may be caused by a dysfunction in the tear secreting glands themselves or in the neuronal circuit regulating these glands. Furthermore, the dry eye condition itself may modify the properties of corneal afferents and affect their ability to regulate secretion, a possibility just now being explored.
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menthol activation of corneal cool cells induces trpm8 mediated Lacrimation but not nociceptive responses in rodents
Investigative Ophthalmology & Visual Science, 2012Co-Authors: Ashlee Robbins, Masayuki Kurose, Barbara J Winterson, Ian D MengAbstract:Purpose Stimulation to the cornea via noxious chemical and mechanical means evokes tearing, blinking, and pain. In contrast, mild cooling of the ocular surface has been reported to increase Lacrimation via activation of corneal cool primary afferent neurons. The purpose of our study was to determine whether menthol induces corneal cool cell activity and Lacrimation via the transient receptor potential melastatin-8 (TRPM8) channel without evoking nociceptive responses. Methods Tear measurements were made using a cotton thread in TRPM8 wild type and knockout mice after application of menthol (0.05-50 mM) to the cornea. In additional studies, nocifensive responses (eye swiping and lid closure) were quantified following cornea menthol application. Trigeminal ganglion electrophysiologic single unit recordings were performed in rats to determine the effect of low and high concentrations of menthol on corneal cool cells. Results At low concentrations, menthol increased tear production in TRPM8 wild type and heterozygous animals, but had no effect in TRPM8 knockout mice, while nocifensive responses remained unaffected. At the highest concentration, menthol (50 mM) increased tearing and nocifensive responses in TRPM8 wild type and knockout animals. A low concentration of menthol (0.1 mM) increased cool cell activity, yet a high concentration of menthol (50 mM) had no effect. Conclusions These studies indicated that low concentrations of menthol can increase Lacrimation via TRPM8 channels without evoking nocifensive behaviors. At high concentrations, menthol can induce Lacrimation and nocifensive behaviors in a TRPM8 independent mechanism. The increase in Lacrimation is likely due to an increase in cool cell activity.
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cold sensitive corneal afferents respond to a variety of ocular stimuli central to tear production implications for dry eye disease
Investigative Ophthalmology & Visual Science, 2010Co-Authors: Harumitsu Hirata, Ian D MengAbstract:Purpose. To investigate the response characteristics of the corneal afferents that detect ocular conditions critical to the activation of the “afferent limb” of the Lacrimation reflex.
Hiroshi Toshida - One of the best experts on this subject based on the ideXlab platform.
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preganglionic parasympathetic denervation rabbit model for innervation studies
Cornea, 2018Co-Authors: Hiroshi Toshida, Chikako SutoAbstract:PURPOSE: Tear secretion from the main lacrimal gland (LG) is mainly regulated by parasympathetic nerves. We performed several innervation studies to investigate Lacrimation. METHODS: In male rabbits, we performed a retrograde dye-tracing study of LG innervation, evaluated preganglionic parasympathetic denervation, and administered glial cell-derived neurotrophic factor (GDNF) in the surgical area after parasympathetic denervation. RESULTS: Accumulation of fluorescent dye was observed in the pterygopalatine ganglion cells on the same side as the dye injection into the main LG. Fewer stained cells were observed in the cervical and trigeminal ganglia. After parasympathetic denervation surgery, tear secretion was decreased, and fluorescein and rose bengal staining scores were increased at day 1 after surgery and remained increased for 3 months on the denervated side only. Most of the effects in rabbits with parasympathetic denervation were not recovered by administration of GDNF. CONCLUSIONS: The main LG is primarily innervated by parasympathetic nerves to stimulate tear secretion. After preganglionic parasympathetic denervation, Lacrimation was decreased, resulting in dry eyes, and this was maintained for at least 3 months. Administration of GDNF only minimally altered the effects of denervation.
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Effects of Preganglionic Parasympathetic Denervation on the Rabbit Lacrimation
Advances in experimental medicine and biology, 2002Co-Authors: Hiroshi Toshida, Roger W. BeuermanAbstract:Lacrimal gland fluid secretion is under neural control. Parasympathetic nerve fibers, with preganglionic origins in the seventh cranial nerve, innervate the lacrimal gland, and the secretory action and signal transduction of acinar cells of this gland are well known.1–4 Although the importance of parasympathetic control of Lacrimation is recognized, few basic studies have investigated the function of ganglionic control as a secretomotor neural system in secretion of tear fluid in vivo.5 In the present study, the effects of acute severing of the preganglionic parasympathetic nerve in normal rabbit produced a dry eye condition with rapid onset.
Markus Naumann - One of the best experts on this subject based on the ideXlab platform.
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successful treatment of crocodile tears by injection of botulinum toxin into the lacrimal gland a case report
Ophthalmology, 1999Co-Authors: Randolf Riemann, Stefan Pfennigsdorf, Elke Riemann, Markus NaumannAbstract:Abstract Objective Pathologic Lacrimation (crocodile tears) is a rare but stigmatizing symptom after facial nerve paralysis. The aim of this pilot study was to examine whether botulinum toxin injection into the lacrimal gland is effective in reducing pathologic tear secretion. Design Case report. Intervention One patient who had crocodile tears after a zoster oticus infection received a botulinum toxin injection (2.5 mouse units) into the lacrimal gland. Testing Before injection, 1 week, 1 month, and 6 months after injection, patient's Lacrimation was assessed by a Schirmer test. Results The Lacrimation of the injected eye was reduced after 1 week and equal after 1 month when compared to the healthy side. After 6 months, hyperLacrimation reoccurred. No side effects were observed. Conclusion Intraglandular injection of botulinum toxin into the lacrimal gland may serve as a sufficient therapy for crocodile tears.
Richard B Lipton - One of the best experts on this subject based on the ideXlab platform.
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Brief Report Cluster headache associated with a sixth nerve palsy: A case report
2016Co-Authors: Brian M Grosberg, Sarah Vollbracht, Matthew S Robbins, Richard B LiptonAbstract:Background: Cluster headache is a rare primary headache disorder characterized by recurrent, stereotyped short-lasting attacks of severe, unilateral head pain accompanied by autonomic symptoms. Methods/results: Ophthalmic features such as conjunctival injection, Lacrimation, ptosis and miosis occur in the vast majority of patients with cluster headache, whereas co-existent ocular movement disorders are rare. Conclusions: To the best of our knowledge, only two documented cases of cluster headache with external ocular movement disorders have been reported. We describe herein an additional case with this unusual finding and discuss the putative pathophysiology of cluster headache associated with ophthalmoparesis
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cluster headache associated with a sixth nerve palsy a case report
Cephalalgia, 2011Co-Authors: Brian M Grosberg, Sarah Vollbracht, Matthew S Robbins, Richard B LiptonAbstract:Background: Cluster headache is a rare primary headache disorder characterized by recurrent, stereotyped short-lasting attacks of severe, unilateral head pain accompanied by autonomic symptoms.Methods/results: Ophthalmic features such as conjunctival injection, Lacrimation, ptosis and miosis occur in the vast majority of patients with cluster headache, whereas co-existent ocular movement disorders are rare.Conclusions: To the best of our knowledge, only two documented cases of cluster headache with external ocular movement disorders have been reported. We describe herein an additional case with this unusual finding and discuss the putative pathophysiology of cluster headache associated with ophthalmoparesis.
