China
Africa
Explore chapters and articles related to this topic
An Approach to Pupillary Disorders
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Sarosh M. Katrak, Azad M. Irani
The pupillary constrictor muscle is innervated by the parasympathetic neurons. The preganglionic fibers originate in the ipsilateral Edinger-Westphal nucleus in the tectum of the midbrain. The fibers course ventrally through the midbrain to emerge in the interpeduncular fossa along with other fibers of the oculomotor nerve. These parasympathetic fibers remain dorsal and superficial throughout the course of the third cranial nerve in the subarachnoid space. Hence, these fibers are more susceptible to extrinsic compression (e.g., posterior communicating artery aneurysm) and relatively protected from ischemic insults as the vasa nervorum lies deep within the substance of the oculomotor nerve. These preganglionic parasympathetic fibers terminate in the ciliary ganglion within the orbit. Postganglionic parasympathetic fibers pass through the sclera as the short ciliary nerves and innervate the pupillary constrictor fibers (Figure 14.2). Activation of its muscarinic (M3) cholinergic receptors produces constriction or miosis of the pupil. An interesting anatomical fact is that only 3–5% of these fibers terminate in the iris sphincter muscle. The remainder terminate in the ciliary muscles that control accommodation [2]. The importance of this will be discussed later.
Miscellaneous
Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
The pupillary light reflex constricts the pupil in response to light, through the innervation of the iris sphincter muscle. This is the result of the neuroanatomical pathways described below. Pupillary light reflex is used to assess the brain stem function. Abnormal pupillary light reflex can be found in optic nerve and oculomotor nerve damage, brain stem lesions and in use of medications such as barbiturates.
The nervous system
Published in Peter Kopelman, Dame Jane Dacre, Handbook of Clinical Skills, 2019
Peter Kopelman, Dame Jane Dacre
Control of pupillary size The size of the pupil is controlled by two divisions of the autonomic nervous system acting mainly in response to the level of illumination and distance of focus. The iris sphincter muscle makes the pupil smaller (miosis), and is innervated by parasympathetic nerves; the iris dilator muscle makes the pupil larger (mydriasis), and is innervated by sympathetic nerves.
Neuro-Ophthalmic Literature Review
Published in Neuro-Ophthalmology, 2022
David A. Bellows, Noel C.Y. Chan, John J. Chen, Hui-Chen Cheng, Peter W MacIntosh, Jenny A. Nij Bijvank, Michael S. Vaphiades, Xiaojun Zhang
The authors described a 73-year-old man who developed a left complete, pupil-sparing third cranial nerve palsy who was found to have a paraclinoid meningioma in the left cavernous sinus. As compressive lesions are expected to impair the iris sphincter muscle, no intervention was recommended and the palsy spontaneously improved within 3 months indicating a vasculopathic nature. They also described a 54-year-old woman with diabetes and a complete third nerve palsy with a dilated, nonreactive pupil. Initial CTA was reported as normal, but a re-review of imaging revealed a posterior communicating artery aneurysm and immediate intervention to coil the aneurysm occurred. The authors concluded that the “Rule of the Pupil” is still important in the modern neuroimaging era as demonstrated in their cases of incidentally found lesions along the course of the oculomotor nerve and missed radiological findings, respectively.
Isolated Internal Ophthalmoplegia Secondary to Herpes Zoster Ophthalmicus: A Rare Case Report
Published in Neuro-Ophthalmology, 2020
Dilek Top Karti, Dilara Aktert, Nese Celebisoy
Internal ophthalmoplegia is a clinical condition that affects pupil function without affecting the eye movements. Extraocular muscle palsies and internal ophthalmoplegia may occur in 31% of the patients with HZO.3 Although the cause of internal ophthalmoplegia in HZO remains unclear, it is considered to result from a viral ganglionitis. As a result of parasympathetic denervation of the iris sphincter muscle, the pupil on the affected side is larger with the anisocoria being more prominent in bright light.13 Pharmacological testing with 0.1% pilocarpine, which is a topical parasympathomimetic agent, causes pupillary constriction due to denervation supersensitivity of the iris sphincter. However, Assal et al.3 reported that the pupillary constriction with 0.1% pilocarpine could occur some time later after the development of internal ophthalmoplegia due to delayed denervation supersensitivity of the iris sphincter. This may explain why our patient’s pupil did not respond to 0.1% pilocarpine. Previous reports have indicated that internal ophthalmoplegia can persist for six months to five years following HZO.14,15 In our case, the internal ophthalmoplegia did not improve during four months follow-up.
Static and dynamic pupil characteristics in pseudoexfoliation syndrome and glaucoma
Published in Clinical and Experimental Optometry, 2020
Kemal Tekin, Hasan Kiziltoprak, Mehmet Ali Sekeroglu, Esat Yetkin, Serdar Bayraktar, Pelin Yilmazbas
Eyes with PES often have pupil abnormalities that are likely due to the progressive accumulation of pseudoexfoliative material in the iris. Additionally, eyes with PES usually show weak pupil dilation mainly because of the rigidity and fibrosis caused by iris sphincter muscle involvement. There are only limited studies evaluating the static and dynamic pupil characteristics of eyes with PES.2015 Ulviye et al.2015 assessed the pupil diameters of patients with PES in scotopic, mesopic, photopic and dynamic conditions and found that all investigated pupil measurements are statistically significantly lower in patients with PES compared to control subjects. These altered pupil sizes and dynamics were also observed even in the unaffected eyes of cases with clinically unilateral PES.2008