China
Africa
Explore chapters and articles related to this topic
Preclinical Toxicology/Safety Considerations in the Development of Ophthalmic Drugs and Devices
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Robert B. Hackett, Michael E. Stern
This model is included in this chapter because it is the only technique currently available to preclinically evaluate topical ocular comfort. It is, however, very complex and not suitable for routine comfort screening. A rabbit or other species is placed under deep urethane anesthesia. A pharyngeal ring is affixed to the eye using the conjunctiva. A 2 ml chamber is attached to the pharyngeal ring and a moist chamber is formed over the cornea to protect the corneal epithelium. The orbital tissue is then excavated to expose the optic nerve. The long ciliary nerve, sensory to the cornea, runs just superficially to the optic nerve. A hook electrode is placed under the long ciliary nerve where it monitors nerve traffic moving centrally from the ocular surface. Once baseline nerve traffic is determined, formulations can be placed into the chamber and the reactive nerve traffic is monitored.
Miscellaneous
Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
The eye receives supply from both the parasympathetic and the sympathetic fibres (Figure 7.7). Parasympathetic supplyThe preganglionic fibres originate in the Edinger-Westphal nucleus in the brain stem and then pass in the third cranial nerve to the ciliary ganglion. The postganglionic fibres then enter the eye via the short ciliary nerve and innervate the ciliary muscles.Activation of the parasympathetic pathway constricts the pupil (miosis).Sympathetic supplyThis originates in the hypothalamus, passing through the midbrain (uncrossed) and lateral medulla and emerges from T1 (close proximity to the lung apex) and passes to the superior cervical ganglion via the dorsal roots. The superior cervical ganglion is located deep to the carotid sheath at the level of the second and third cervical vertebrae. From there, the fibres synapse and project cranially and innervate the eye either via the short ciliary nerve, long ciliary nerve or directly into the orbit. These will then innervate the radial fibres of the iris.Activation of the sympathetic pathway dilates the pupil (mydriasis).
Uveitis
Published in Mostafa Khalil, Omar Kouli, The Duke Elder Exam of Ophthalmology, 2019
Mostafa Khalil, Omar Kouli, Obaid Kousha
The stroma is composed of many cells including melanocytes (pigmented cells) that gives the iris its colour. It has two zones: The pupillary zone extends from the pupillary edge to the collarette (thickest part of the iris that separates the two zones). The sphincter pupillae is located here. It is a smooth muscle responsible for pupillary constriction with parasympathetic innervation (CNIII) via short ciliary nerves.The ciliary zone extends from the collarette to the origin of the iris at the ciliary body. The dilator pupillae is located here. It is a smooth muscle responsible for pupillary dilatation with sympathetic innervation via long ciliary nerves.
Ocular manifestations of endocrine disorders
Published in Clinical and Experimental Optometry, 2022
M Hossein Nowroozzadeh, Sarah Thornton, Alison Watson, Zeba A Syed, Reza Razeghinejad
Panretinal photocoagulation has been the standard treatment of proliferative diabetic retinopathy for decades.4 The outer retina is destructed in the laser-treated areas, diminishing oxygen demand of the retinal tissue and increasing oxygen to the inner retinal layers by facilitating diffusion from the choroid. Collectively, these mechanisms restore a more normal supply-demand balance in the retina and decrease profuse secretion of vasoproliferative growth factors such as vascular-endothelial growth-factor. Therefore, laser stops the process of exuberant neovascularization and prevents its later complications (Figure 1). Exacerbation of macular oedema and peripheral and night vision loss are among the most common complications of panretinal photocoagulation. In some cases, inadvertent treatment of long ciliary nerves during laser therapy may lead to transient or permanent loss of corneal sensation, decreased accommodation, sluggish pupillary reflex, and glare.13
Advances in the Medical Management of Neurotrophic Keratitis
Published in Seminars in Ophthalmology, 2021
Thomas H. Dohlman, Rohan Bir Singh, Reza Dana
Neurotrophic keratitis (NK) is a disorder of the cornea caused by impaired sensory innervation, with subsequent loss of corneal epithelial integrity and impaired wound healing. Nasociliary and long ciliary nerves derived from the ophthalmic branch of the trigeminal nerve form the sensory neuronal component of the cornea.1 With over 7,500 receptors/mm,2 the cornea is one of the most densely innervated tissues in the body, and these sensory nerves are highly sensitive to nociception, cold and pressure stimuli.2,3 Corneal innervation plays a critical protective role for the cornea as these nerves stimulate tear production and modulate the blink response.4 They are also an important source of neuropeptides and trophic factors that promote corneal epithelial health and integrity. Key neuropeptides include substance P and calcitonin gene related peptide, while trophic factors include nerve growth factor, brain-derived nerve factor, glial-derived nerve factor and epidermal growth factor, among others.5–8
Transient anisocoria after a traumatic cervical spinal cord injury: A case report
Published in The Journal of Spinal Cord Medicine, 2020
Paul Overdorf, Gary J. Farkas, Natasha Romanoski
The sympathetic innervation to the eye is from the superior cervical ganglion (Fig. 1). The superior cervical ganglion lies anterior to the transverse processes of the second and third cervical vertebra. Anterior to the ganglion lies the carotid sheath with the internal carotid artery, internal jugular vein, and vagus nerve, while the longus capitis muscle is found posterior to the ganglion. Postganglionic sympathetic fibers from the superior cervical ganglion are distributed onto the internal carotid artery and help to form the internal carotid nerve plexus, which ascends on the internal carotid artery into the carotid canal to enter the cranial cavity (Fig. 1).11 Once in the cranial cavity, postganglionic fibers from the internal carotid nerve plexus travel on the nasociliary nerve of the ophthalmic division of the trigeminal nerve, while other fibers continue from the internal carotid nerve plexus as the sympathetic root of the ciliary ganglion.12 The sympathetic root of the ciliary ganglion traverses the ciliary ganglion without synapsing (Fig. 1). These nerves then travel on the short ciliary nerves of the ciliary ganglion to the eye where they innervate the dilator pupillae muscle. Some of these postganglionic sympathetic fibers also travel on the long ciliary nerve, a nerve branch of the nasociliary nerve, to reach the eye (Fig. 1). Sympathetic activation of the dilator pupillae muscle dilates the pupil.11,12