Monographs of Topical Drugs that Have Caused Contact Allergy/Allergic Contact Dermatitis
Anton C. de Groot in Monographs in Contact Allergy, 2021
Cyclopentolate is a parasympatholytic anticholinergic drug. Administered in the eye, cyclopentolate blocks the acetylcholine receptor in the sphincter muscle of the iris and the ciliary muscle, thereby preventing contraction. This produces mydriasis (excessive dilation of the pupil) and cycloplegia (paralysis of the ciliary muscle of the eye), which facilitates ophthalmic diagnostic procedures. Cyclopentolate acts more quickly than atropine and has a shorter duration of action (1). In pharmaceutical products, cyclopentolate is employed as cyclopentolate hydrochloride (CAS number 5870-29-1, EC number 227-521-8, molecular formula C17H26ClNO3) (1).
Antagonists at Muscarinic Cholinergic Receptors
Kenneth J. Broadley in Autonomic Pharmacology, 2017
Atropinic drugs are instilled into the eyes as drops for their mydriatic and cycloplegic effects. The dilation of the pupil and abolition of the response to light permits examination of the retina and optic disc. Cycloplegia occurs with higher doses, the paralysis of accommodation for near vision leading to blurred sight. The poor response to light (photophobia) necessitates the patient having to wear dark glasses and this, combined with the blurred vision, are particularly hazardous for patients leaving the examination room when long-acting agents like hyoscine and atropine are used. It is therefore preferred to employ shorter-acting atropinics including homatropine (Table 9.1), cyclopentolate and tropicamide (Table 9.4).
The Special Sense Organs and Their Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
Muscular and neural abnormalities may also affect vision. Esotropia, in which the eyeball turns inward, is also called convergent strabismus or "crosseye" and is an involuntary deviation of the eyes from the normal position caused by a muscular defect or weakness in coordination. Exotropia, also called divergent strabismus or "walleye," is a lateral deviation or outward turning of the eyeball, resulting in diplopia (double vision). Dysfunction of the eye muscles or their innervation (nerve supply) can cause a defect in ocular movement called ocular paralysis, Cycloplegia results from temporary paralysis of the ciliary muscle and zonules, causing decreased accommodation and blurred vision; cycloplegia can be caused by anticholinergic agents. Ametropia (from the Greek word ametros, "without measure") is an inability of the eye to focus images correctly on the retina, resulting in a refractive disorder such as diplopia, myopia (nearsightedness), hyperopia (farsightedness), astigmatism, or presbyopia ("aging eye").
Should “Retro-ocular Pain, Photophobia and Visual Acuity Loss” Be Recognised as a Distinct Entity? The ROPPVAL Syndrome
Published in Neuro-Ophthalmology, 2021
Francesco Pellegrini, Erika Mandarà, Daniele Brocca
Photophobia is defined as a painful sensation to light exposure. Recently, a novel population of retinal neurons, intrinsically photosensitive retinal ganglion cells (IPRGCs), have been identified as photophobia transducers in the eye.13 Notably, these IPRGCs project onto trigeminal neurons14 and pain nuclei in the thalamus,15,16 which are also involved in migraine pathogenesis. We believe that “stimuli”, like those involved in migraine, may trigger the trigeminal nerve fibres which collect painful light sensations from the eye when activated by IPRGCs. We believe that the ciliary ganglia located in orbital-fat behind the globe may play a major role in determining this stereotyped syndrome, because of the relief of symptoms when amitriptyline or cyclopentolate drops are administered. We can speculate that activated trigeminal pain-sensing fibres and light-activated fibres may affect parasympathetic neurons and/or vice versa. Cyclopentolate is an anticholinergic drug, thus paralyses the iris sphincter constrictor and ciliary body muscles. Cycloplegia is commonly used in ophthalmology to reduce inflammation and pain due to different ocular conditions such as iritis where the ciliary body over-contraction is the main cause of pain.
The effect of cycloplegia on biometric measurements using swept‐source optical coherence tomography‐based biometry
Published in Clinical and Experimental Optometry, 2019
Sehnaz Ozcaliskan, Nursal Melda Yenerel
In this study, the effect of cycloplegia in AL, K1 and K2, ACD, AQD, LT, CCT and WTW measurements obtained with IOL Master 700 were evaluated. This device also has the ability to measure the pupil diameter. That parameter was not included in our study, because pupil diameter already increases after pupil dilation. We observed a significant increase in ACD, AQD, CCT and a significant decrease in LT after cycloplegia. Higashiyama et al.16 evaluated changes in the anterior segment after cycloplegia with a biometer using SS‐OCT in paediatric patients. They observed an increased ACD and decreased LT after cycloplegia. Cycloplegic agents cause paralysis of the ciliary muscle, pupillary dilation and eliminates accommodation. During accommodation, the LT and anterior lens curvature changes, which would lead to a change in anterior segment structure.2015 When accommodation is inhibited, the lens becomes flatter and moves posteriorly. Thereby, LT decreases and anterior chamber deepens. Many studies explain the changes in ACD and LT after cycloplegia by this accommodation blockade mechanism. As a result of these anterior segment changes, AQD values will be increased.
Effect of Cycloplegia on Refractive Error Measure in Chinese School Students
Published in Ophthalmic Epidemiology, 2022
Fang Gu, Hans M. Gao, Xin Zheng, Lei Gu, Jianyao Huang, Jia Meng, Juanjuan Li, Lei Gao, Jianyong Wang, Ronghua Zhang, Jianqin Shen, Gui-Shuang Ying, Hongguang Cui
Assessment of the refractive error of the eye under cycloplegia is still considered to be the gold standard when measuring refractive error in children.13 Because of the robust accommodative abilities of pediatric eyes, cycloplegic agents, such as atropine, cyclopentolate, or tropicamide, must be administered to paralyze the accommodative system.14,15 When cycloplegic agents are withheld, clinicians tend to overestimate the prevalence and severity of myopia.15–17 Although cycloplegia results in more accurate measurements of refractive error, cycloplegic agents may be associated with adverse effects, including blurred vision, photophobia, and glare.18 As a result, many children and parents refuse cycloplegia when undergoing refractive error screening and exams, leading to erroneous measurements of refractive error.19–21 Non-cycloplegic refractive error is still commonly used for determining the prevalence, or incidence of myopia, particularly in population-based epidemiological studies of myopia.
Related Knowledge Centers
- Accommodation
- Ciliary Muscle
- Cyclopentolate
- Eye
- Mydriasis
- Presbyopia
- Refraction
- Paralysis
- Atropine
- Muscarinic Acetylcholine Receptor