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Synechia (eye)
Ocular synechia is an eye condition where the iris adheres to either the cornea (i.e. ''anterior synechia'') or lens (i.e. ''posterior synechia'').F. Salmon, J. (2019) Kanski’s Clinical Ophthalmology. 9th Edition, Elsevier. Synechiae can be caused by ocular trauma, iritis or iridocyclitis and may lead to certain types of glaucoma. It is sometimes visible on careful examination but usually more easily through an ophthalmoscope or slit-lamp. Anterior synechia causes closed angle glaucoma, which means that the iris closes the drainage way of aqueous humour which in turn raises the intraocular pressure. Posterior synechia can be observed in cases of anterior uveitis secondary to severe to moderate bacterial keratitis. Posterior synechia also cause glaucoma, but with a different mechanism. In posterior synechia, the iris adheres to the lens, blocking the flow of aqueous humor from the posterior chamber to the anterior chamber. This blocked drainage raises the intraocular pre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intraocular Pressure
Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk of glaucoma. Most tonometers are calibrated to measure pressure in millimeters of mercury (mmHg). Physiology Intraocular pressure is determined by the production and drainage of aqueous humour by the ciliary body and its drainage via the trabecular meshwork and uveoscleral outflow. The reason for this is because the vitreous humour in the posterior segment has a relatively fixed volume and thus does not affect intraocular pressure regulation. An important quantitative relationship (Goldmann's equation) is as follows: :P_o = \frac + P_v Where: * P_o is the IOP in millimeters of mercury (mmHg) * F the rate of aqueous humour formation in microliters per minute (μL/min) * U the resorption of aqueous humour through the uveoscleral route (μL/min) * C is the facility of outflow in mic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Travoprost
Travoprost, sold under the brand name Travatan among others, is a medication used to treat high pressure inside the eye including glaucoma. Specifically it is used for open angle glaucoma when other agents are not sufficient. It is used as an eye drop. Effects generally occur within two hours. Common side effects include red eyes, blurry vision, eye pain, dry eyes, and change in color of the eyes. Other significant side effects may include cataracts. Use during pregnancy or breastfeeding is generally not recommended. It is a prostaglandin analog and works by increasing the outflow of aqueous humor, aqueous fluid from the eyes. Travoprost was approved for medical use in the United States and in the European Union in 2001. It is available as a generic medication in the United Kingdom. In 2020, it was the 304th most commonly prescribed medication in the United States, with more than 1million prescriptions. Medical uses Travoprost is used to treat high pressure inside the eye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prostaglandin Analogue
Prostaglandin analogues are a class of drugs that bind to a prostaglandin receptor. Wider use of prostaglandin analogues is limited by unwanted side effects and their abortive potential. Uses Prostaglandin analogues such as misoprostol are used in treatment of duodenal and gastric ulcers. Misoprostol and other prostaglandin analogues protect the lining of the gastrointestinal tract from harmful stomach acid and are especially indicated for the elderly on continuous doses of NSAIDs. In the field of ophthalmology, drugs of this class are used to lower intraocular pressure (IOP) in people with glaucoma. Up until the late 1970s prostaglandins were thought to raise IOP, but a paper published in 1977 showed that prostaglandin F2α lowered it, and subsequent studies found that this was due to increasing the outflow of aqueous humor, mainly by relaxing the ciliary muscle, and possibly also due to changes in extracellular matrix and to widening of spaces within the trabecular meshwo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involved in a wide range of physiological processes, including stress response, immune response, and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte levels, and behavior. Some common naturally occurring steroid hormones are cortisol (), corticosterone (), cortisone () and aldosterone () (cortisone and aldosterone are isomers). The main corticosteroids produced by the adrenal cortex are cortisol and aldosterone. The etymology of the '' cortico-'' part of the name refers to the adrenal cortex, which makes these steroid hormones. Thus a corticosteroid is a "cortex steroid". Classes * Glucocorticoids such as cortisol affect carbohydrate, fat, and protein metabolism, and have anti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pupil
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil. The size of the pupil is controlled by the iris, and varies depending on many factors, the most significant being the amount of light in the environment. The term "pupil" was coined by Gerard of Cremona. In humans, the pupil is circular, but its shape varies between species; some cats, reptiles, and foxes have vertical slit pupils, goats and sheep have horizontally oriented pupils, and some catfish have annular types. In optical terms, the anatomical pupil is the eye's aperture and the iris is the aperture stop. The image of the pupil as seen from o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pupillary Dilation
Pupillary response is a physiological response that varies the size of the pupil between 1.5 mm and 8 mm, via the optic and oculomotor cranial nerve. A constriction response (miosis), is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/ opioids or anti-hypertension medications. Constriction of the pupil occurs when the circular muscle, controlled by the parasympathetic nervous system (PSNS), contracts, and also to an extent when the radial muscle relaxes. A dilation response (mydriasis), is the widening of the pupil and may be caused by adrenaline; anticholinergic agents; stimulant drugs such as MDMA, cocaine, and amphetamines; and some hallucinogenics (e.g. LSD). Dilation of the pupil occurs when the smooth cells of the radial muscle, controlled by the sympathetic nervous system (SNS), contract, and also when the cells of the iris sphincter muscle relax. The responses can have a variety of causes, from an involuntary reflex reac ... [...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 dry mouth, abnormally large pupils, urinary retention, constipation, and a fast heart rate. It should generally not be used in people with closed-angle glaucoma. While there is no evidence that its use during pregnancy causes birth defects, this has not been well studied so sound clinical judgment should be used. It is likely safe during breastfeeding. It is an antimuscarinic (a type of anticholinergic) that works by inhibit ... [...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. Homatropine hydrobromide is on the World Health Organization's List of Essential Medicines. It is an antagonist of all five muscarinic acetylcholine receptors. Side effects * Blurred vision * Sensitivity to light Contraindications * Untreated glaucoma * Myasthenia gravis * Se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cycloplegic
Cycloplegia is paralysis of the ciliary muscle of the Human eye, eye, resulting in a loss of accommodation (eye), 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 antagonists such as atropine, cyclopentolate, homatropine, Hyoscine hydrobromide, 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 treatm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mydriatic
Mydriasis is the dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response. Non-physiological causes of mydriasis include disease, trauma, or the use of certain types of drugs. It may also be of unknown cause. Normally, as part of the pupillary light reflex, the pupil dilates in the dark and constricts in the light to respectively improve vividity at night and to protect the retina from sunlight damage during the day. A ''mydriatic'' pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a mydriasis. More generally, mydriasis also refers to the natural dilation of pupils, for instance in low light conditions or under sympathetic stimulation. Mydriasis is frequently induced by drugs for certain ophthalmic examinations and procedures, particularly those requiring visual access to the retina. Fixed, unilater ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Closed Angle Glaucoma
Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of sight" because the loss of vision usually occurs slowly over a long period of time. A major risk factor for glaucoma is increased pressure within the eye, known as intraocular pressure (IOP). It is associated with old age, a family history of glaucoma, and certain medical conditions or the use of some medications. The word ''glaucoma'' comes from the Ancient Greek word (), meaning 'gleaming, blue-green, gray'. Of the different types of glaucoma, the most common are called open-angle glaucoma and closed-angle glaucoma. Inside the eye, a liquid called aqueous humor helps to maintain shape and provides nutrients. The aqueous humor normally drains through the trabecular meshwork. In open-angle glaucoma, the draining is impeded, causing the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
