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Pilocarpine
Published in Anton C. de Groot, Monographs in Contact Allergy, 2021
Pilocarpine is a natural alkaloid extracted from plants of the genus Pilocarpus with cholinergic agonist activity. As a cholinergic parasympathomimetic agent, it predominantly binds to muscarinic receptors, thereby inducing exocrine gland secretion and stimulating smooth muscle in the bronchi, urinary tract, biliary tract, and intestinal tract. When applied topically to the eye, this agent stimulates the sphincter pupillae to contract, resulting in miosis. It also stimulates the ciliary muscle to contract, resulting in spasm of accommodation and may cause a transitory rise in intraocular pressure followed by a more persistent fall due to opening of the trabecular meshwork and an increase in the outflow of aqueous humor. Pilocarpine is indicated for the treatment of radiation-induced dry mouth (xerostomia) and symptoms of dry mouth in patients with Sjögren’s syndrome. It is also used as a miotic in the treatment of glaucoma. In pharmaceutical products, pilocarpine is employed as pilocarpine hydrochloride (CAS number 54-71-7, EC number 200-212-5, molecular formula C11H17CIN2O2) (1).
Cholinergic Agonists
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
Rupali Patil, Aman Upaganlawar
Physostigmine is used in atony of intestine and bladder as it increases their motility. It can be used to treat glaucoma as it produces miosis and spasm of accommodation as well as a lowering of IOP when instilled in the eye. It can be used to treat glaucoma, but pilocarpine is more effective. Also, it is used in the treatment of overdosage of drugs with anticholinergic drugs, such as atropine, phenothiazine, and tricyclic antidepressants (Brunton, 2011).
Parasympathomimetic Amines
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
Parasympathomimetics interact with M3 muscarinic receptors on the circular (sphincter pupillae) muscle around the pupil margin of the iris and cause contraction. The pupil may be constricted (miosis) to ‘pinpoint’ dimension. The radial muscle is not innervated by parasympathetic nerves and does not respond to muscarinic agonists. The ciliary muscle contracts in response to muscarinic agonists acting on M3 receptors and the lense is accommodated for near vision (see Chapter 1, Figure 1.7). Spasm of accommodation in this mode results in blurred vision. The contraction of the pupil away from the canal of Schlemm opens the drainage angle, facilitating the outflow of aqueous humour. This reduces intraocular pressure when raised in glaucoma (see later).
Diagnosis and Management of Post Traumatic Recurrent Unilateral Accommodative Spasm—A Case Report
Published in Journal of Binocular Vision and Ocular Motility, 2022
Praveen Kumar P, Amit Bhowmick, Neha Mahabale, Jameel Rizwana Hussaindeen, Dhanashree Ratra
This case report illustrates the presence of unilateral accommodative spasm, a rare clinical entity, and to the best of our knowledge, there are very few reports that have documented the same.7–12 All these cases of unilateral accommodative spasm were documented to have moderate to severe visual impairment, while our patient had mild visual impairment. The computational eye model to understand the impact of blunt injury demonstrated that the stress on the zonules could cause deformation of the lens.13 Ciliary muscle spasm, when circumference of zonules gets affected, presents with temporary incline toward myopic error.14 It is also reported that the trauma can damage the ciliary ganglion, leading to increased parasympathetic activity.8 In our case, the trivial injury on the left side followed by the traumatic events could have potentially resulted in a shock, leading to unilateral spasm of accommodation. The patient also reported increased stress levels at workplace due to the nature of the armed professions itself. A report by Tokiwa et al. also documented psychogenic etiology to be one of the causes for unilateral accommodative spasm.6 The manifestation of spasm was reported in the unaffected eye when the affected eye was occluded.11 In our report, to understand the manifestation in the unaffected eye, we had examined all the accommodation parameters when the affected eye was occluded.
The impact of smartphone use on accommodative functions: pilot study
Published in Strabismus, 2023
Literature reporting the effect of smartphone use on the eyes falls into three main categories, which are accommodation and vergence issues, eye surface, and blue light.3–5 Only a small number of studies have undertaken a prospective investigation into the effect of smartphone use on measurable functions.6–12 Of note and relevance is the growing body of the literature describing cases of AACE due to excessive smartphone use,13–20 which may result from changes in accommodative and vergence measures.10–12 Lee et al.13 is cited as the initial observer of this scenario where 16 cases of AACE are reported to have improved by 10 prism diopters following reduced smartphone use. Subsequently, perhaps due to the COVID-19 pandemic, further descriptions of over 100 cases are given in the literature of AACE caused by excessive smartphone use.14–20 Excessive smartphone use could be considered more than 4 hours use per day,20 but it was not always stated. The authors are finding similar patient characteristics that demonstrate an increased risk of AACE due to excessive smartphone use. These characteristics include: existing esophoria,16 shorter working distance,19 teenage years,17 and myopia.15,17 The authors of the above studies postulate that abnormal accommodation and vergence responses result in some changes in the medial rectus muscle activation or anatomy.17,18 Interestingly, some authors believe it is the spasm of accommodation that causes the esotropia,14,15 however Van Hoolst et al.19 demonstrated no spasm of accommodation within their AACE case series following refraction and AC/A ratio measurements. Therefore, despite some postulation over the cause of AACE due to smartphone use, there remains further work to identify the effects of smartphone use on the near triad and the preexisting risk factors that may be exacerbated. This pilot study explores the relationship between these functions and smartphone use.
Spasm of the Near Reflex: Literature Review and Proposed Management Strategy
Published in Journal of Binocular Vision and Ocular Motility, 2018
Cogan and Freese coined the term SNR.6 In their landmark paper, they state that “spasm of the near reflex is a distinct entity, not to be confused with convergence excess or isolated spasm of accommodation”.