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Accommodative Spasm
A spasm of accommodation (also known as a ciliary spasm, an accommodation, or accommodative spasm) is a condition in which the ciliary muscle of the eye remains in a constant state of contraction. Normal accommodation allows the eye to "accommodate" for near-vision. However, in a state of perpetual contraction, the ciliary muscle cannot relax when viewing distant objects. This causes vision to blur when attempting to view objects from a distance. This may cause pseudomyopia or latent hyperopia. Although antimuscarinic drops (homoatropine 5%) can be applied topically to relax the muscle, this leaves the individual without any accommodation and, depending on refractive error, unable to see well at near distances. Also, excessive pupil dilation may occur as an unwanted side effect. This dilation may pose a problem since a larger pupil is less efficient at focusing light (see pupil, aperture, and optical aberration for more.) Patients who have accommodative spasm may benefit from bei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliary Muscle
The ciliary muscle is an intrinsic muscle of the eye formed as a ring of smooth muscleSchachar, Ronald A. (2012). "Anatomy and Physiology." (Chapter 4) . in the eye's middle layer, uvea ( vascular layer). It controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humor into Schlemm's canal. It also changes the shape of the lens within the eye but not the size of the pupil which is carried out by the sphincter pupillae muscle and dilator pupillae. Structure Development The ciliary muscle develops from mesenchyme within the choroid and is considered a cranial neural crest derivative.Dudek RW, Fix JD (2004). "Eye" (chapter 9). ''Embryology - Board Review Series'' (3rd edition, illustrated). Lippincott Williams & Wilkins. p. 92. , . Books.Google.com. Retrieved on 2010-01-17 from https://books.google.com/books?id=MmoJQWsJteoC. Nerve supply The ciliary muscle receives parasympathetic fibers from the short ciliary nerves that arise fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplitude Of Accommodation
The amplitude of accommodation is the maximum potential increase in optical power that an eye can achieve in adjusting its focus. It refers to a certain range of object distances for which the retinal image is as sharply focussed as possible. Amplitude of accommodation is measured during routine eye-examination. The closest that a normal eye can focus is typically about 10 cm for a child or young adult. Accommodation then decreases gradually with age, effectively finishing just after age fifty. The average amplitude of accommodation, in diopters, for a patient of a given age was estimated by Hofstetter in 1950 to be 18.5 - (0.30 * patient age in years) with the minimum amplitude of accommodation as 15 - (0.25 * age in years), and the maximum as 25 - (0.40 * age in years). However, Hofstetter's work was based on data from two early surveysDonders F. On the anomalies of the accommodation and refraction of the eye. (W. Moore Trans.) UK: The New Sydenham Society, 1864. p 207-2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cycloplegia
Cycloplegia is paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation. Because of the paralysis of the ciliary muscle, the curvature of the lens can no longer be adjusted to focus on nearby objects. This results in similar problems as those caused by presbyopia, in which the lens has lost elasticity and can also no longer focus on close-by objects. Cycloplegia with accompanying mydriasis (dilation of pupil) is usually due to topical application of muscarinic antagonists such as atropine and cyclopentolate. Belladonna alkaloids are used for testing the error of refraction and examination of eye. Management Cycloplegic drugs are generally muscarinic receptor blockers. These include atropine, cyclopentolate, homatropine, scopolamine and tropicamide. They are indicated for use in cycloplegic refraction (to paralyze the ciliary muscle in order to determine the true refractive error of the eye) and the treatment of uveitis. All cycloplegics are also mydriat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Miosis
Miosis, or myosis (), is excessive constriction of the pupil. citing: Mosby's Medical Dictionary, 8th ed. The opposite condition, , is the dilation of the pupil. Anisocoria is the condition of one being more dilated than the other. Causes Age * Senile miosis (a reduction in the size of a person's pupil in old age)Diseases * ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Optometric Association
The American Optometric Association (AOA), founded in 1898, represents approximately 37,000 doctors of optometry, optometry students and para-optometric assistants and technicians in the United States. Overview The AOA states that: The American Optometric Association represents approximately 39,000 doctors of optometry, optometry students and paraoptometric assistants and technicians. Optometrists serve patients in nearly 6,500 communities across the country, and in 3,500 of those communities are the only eye doctors. Doctors of optometry provide two-thirds of all primary eye care in the United States. Founded in 1898, the AOA is a federation of state, student and armed forces optometric associations. Through these affiliations, the AOA serves members consisting of optometrists, students of optometry, paraoptometric assistants and technicians. Together, the AOA and its affiliates work to provide the public with quality vision and eye care. The AOA has offices in St. Louis, M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perilla Frutescens
''Perilla frutescens'', commonly called deulkkae, perilla or Korean perilla, is a species of ''Perilla'' in the mint family Lamiaceae. It is an annual plant native to Southeast Asia and Indian highlands, and is traditionally grown in the Korean peninsula, southern China, Japan and India as a crop. An edible plant, perilla is grown in gardens and attracts butterflies. It is aromatic with a strong mint-like smell. A variety of this plant, ''P. frutescens'' var. ''crispa'' known as "shiso", is widely grown in Japan. In the United States, perilla is a weed pest, toxic to cattle after ingestion. Names Along with other plants in the genus ''Perilla'', the plant is commonly called "perilla". It is also referred to as Korean perilla, due to its extensive cultivation in Korea and use in Korean cuisine. In the United States, where the plant has become a weed, the plant is known by many names, such as perilla mint, beefsteak plant, purple perilla, Chinese basil, wild basil, blueweed, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitroglycerin (drug)
Nitroglycerin, also known as glyceryl trinitrate (GTN), is a medication used for heart failure, high blood pressure, anal fissures, painful periods, and to treat and prevent chest pain caused by decreased blood flow to the heart (angina) or due to the recreational use of cocaine. This includes chest pain from a heart attack. It is taken by mouth, under the tongue, applied to the skin, or by injection into a vein. Common side effects include headache and low blood pressure. The low blood pressure can be severe. It is unclear if use in pregnancy is safe for the baby. It should not be used together with medications within the PDE5 inhibitor family such as sildenafil due to the risk of low blood pressure. Nitroglycerin is in the nitrate family of medications. While it is not entirely clear how it works, it is believed to function by dilating blood vessels. Nitroglycerin was written about as early as 1846 and came into medical use in 1878. It is on the World Health Organizat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homatropine
Homatropine (Equipin, Isopto Homatropine) is an anticholinergic medication that is an antagonist at muscarinic acetylcholine receptors and thus the parasympathetic nervous system. It is used in eye drops as a cycloplegic (to temporarily paralyze accommodation), and as a mydriatic (to dilate the pupil). The related chemical compound homatropine methylbromide (methylhomatropine) is a different medication. Homatropine is less potent than atropine and has a shorter duration of action. It is available as the hydrobromide salt. Homatropine is also given as an atropine substitute given to reverse the muscarinic and CNS effects associated with indirect cholinomimetic (anti-AChase) administration. It is on the World Health Organization's List of Essential Medicines. Side effects * Blurred vision * Sensitivity to light Contraindications * Untreated glaucoma * Myasthenia gravis * Severe heart failure * Thyrotoxicosis Hyperthyroidism is the condition that occurs due to exc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropicamide
Tropicamide, sold under the brand name Mydriacyl among others, is a medication used to dilate the pupil and help with examination of the eye. Specifically it is used to help examine the back of the eye. It is applied as eye drops. Effects occur within 40 minutes and last for up to a day. Common side effects include blurry vision, increased intraocular pressure, and sensitivity to light. Another rare but severe side effect is psychosis, particularly in children. It is unclear if use during pregnancy is safe for the fetus. Tropicamide is in the antimuscarinic part of the anticholinergic family of medications. It works by making the muscles within the eye unable to respond to nerve signals. Tropicamide was approved for medical use in the United States in 1960. It is on the World Health Organization's List of Essential Medicines. Medical use Tropicamide is an antimuscarinic drug that produces short acting mydriasis (dilation of the pupil) and cycloplegia when applied as eye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atropine
Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent and pesticide poisonings as well as some types of slow heart rate, and to decrease saliva production during surgery. It is typically given intravenously or by injection into a muscle. Eye drops are also available which are used to treat uveitis and early amblyopia. The intravenous solution usually begins working within a minute and lasts half an hour to an hour. Large doses may be required to treat some poisonings. Common side effects include a dry mouth, large pupils, urinary retention, constipation, and a fast heart rate. It should generally not be used in people with angle closure glaucoma. While there is no evidence that its use during pregnancy causes birth defects, that has not been well studied. It is likely safe during breastfeeding. It is an antimuscarinic (a type of anticholinergic) that works by inhibiting the parasympathetic nervous system. Atropine occurs n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclopentolate
Cyclopentolate is a muscarinic antagonist. It is commonly used as an eye drop during pediatric eye examinations to dilate the eye (mydriatic) and prevent the eye from focusing/ accommodating (cycloplegic). Cyclopentolate or atropine can also be administered to reverse muscarinic and central nervous system effects of indirect cholinomimetic (anti-AChase) administration. It is on the World Health Organization's List of Essential Medicines. After instillation of cyclopentolate, pupil dilation (mydriasis) typically lasts up to 24 hours, while paralysis of the ciliary muscle (cycloplegia) typically lasts 6-24 hours. During this time, patients may be more light sensitive than normal and may notice close objects blurred (and possibly distant objects blurred, depending on the patient's visual system). Cyclopentolate is often chosen as a milder, shorter-lasting, cycloplegic alternative to atropine, another cycloplegic agent which lasts much longer. Tropicamide is an even shorter-lastin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Negative Relative Accommodation
Negative relative accommodation (NRA) was proposed by Joseph Kearney of Oxford University in 1967 as a measure of the maximum ability to relax accommodation while maintaining clear, single binocular vision. This measurement is typically obtained by an orthoptist, ophthalmologist or optometrist during an eye examination using a phoropter. After the patient's distance correction is established, the patient is instructed to view small letters on a card 40 cm from the eyes. The examiner adds lenses in +0.25 increments until the patient first reports that they become blurry. The total value of the lenses added to reach this point is the NRA value. High NRA values (above +2.50) might be evidence to over minus, uncorrected hyperopia or latent hyperopia. See also *Amplitude of accommodation *Convergence insufficiency *Positive relative accommodation Positive relative accommodation (PRA) in biology, is a measure of the maximum ability to stimulate eye accommodation while maintaining clear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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