Ocular hypertension 3541477 209177410 2008-04-30T06:15:20Z Bcebul 285010 pathophysiology {{Infobox_Disease | Name = {{PAGENAME}} | Image = | Caption = | DiseasesDB = 5226 | ICD10 = {{ICD10|H|40|0|h|40}} | ICD9 = {{ICD9|365.04}} | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = oph | eMedicineTopic = 578 | MeshID = D009798 | }} '''Ocular hypertension''' (OHT) is [[intraocular pressure]] higher than normal in the absence of [[optic nerve]] damage or [[visual field]] loss.<ref>[http://www.aao.org/aao/patients/eyemd/upload/Ocular-Hypertension-Glaucoma-and-Eye-Drops.pdf American Academy of Ophthalmology]</ref><ref>[http://www.aoa.org/x1799.xml American Optometric Association]</ref> Current consensus in [[ophthalmology]] defines normal introcular pressure (IOP) as that between 10 mmHg and 21 mmHg.<ref>[http://www.webmd.com/hw/lab_tests/hw201323.asp webMD]</ref><ref>[http://www.emedicinehealth.com/articles/14545-1.asp eMedicine - Glaucoma Overview]</ref> Elevated IOP is the most important risk factor for [[glaucoma]], so those with ocular hypertension are frequently considered to have a greater chance of developing the condition. Intraocular pressure can increase when a patient lies down. There is evidence that some glaucoma patients (e.g., normal tension glaucoma patients) with normal IOP while sitting or standing may have intraocular pressure that is elevated enough to cause problems when they are lying down. ==Pathophysiology== [[Intraocular pressure]] is mainly maintained by the liquid [[aqueous humor]], which is produced by the [[ciliary body]] of the eye. Aqueous humor normally does not go into the posterior segment of the eye; it is kept out of this area by the lens and the Zonule of Zinn. Instead, it stays only in the anterior segment, which is divided into the anterior and posterior chambers. While the anterior and posterior ''chambers'' are very similarly named to the anterior and posterior ''segments'', they are '''not''' synonymous. The anterior and posterior chambers are both parts of the anterior segment, which is an important distinction to make in the understanding of the two main mechanisms of ocular hypertension. When the ciliary bodies produce the aqueous humor, it first flows into the posterior chamber (bounded by the lens and the iris). It then flows through the pupil of the iris into the anterior chamber (bounded by the iris and the cornea). From here, it flows through a structure known as the trabecular meshwork to enter the normal body circulation. Thus, the two main mechanisms of ocular hypertension are an increased production of aqueous humor, or a decreased outflow of aqueous humor. ==Treatment== ===Medication=== Ocular hypertension are mostly treated with [[pilocarpine]], [[timolol]], [[acetazolamide]] and [[clonidine]]<ref name=Rang146> {{cite book |author=Rang, H. P. |title=Pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2003 |pages= |isbn=0-443-07145-4 |oclc= |doi=}} Page 146 </ref>. There are also other, less commonly used, alternatives. Eye drops may initially be started either in one or in both eyes.<ref name="bmc ophthalmol">[ http://www.biomedcentral.com/1471-2415/7/17 Interpretation of uniocular and binocular trials of glaucoma medications]</ref> {|class="wikitable" |+Comparison table of ocular antihypertensives |- !Medication !Mechanism !Dosage form<ref name=Rang146unless> Unless else specified in boxes, then ref is: {{cite book |author=Rang, H. P. |title=Pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2003 |pages= |isbn=0-443-07145-4 |oclc= |doi=}} Page 146 </ref> !Adverse effects<ref name=Rang146unless/> |- |[[pilocarpine]] |[[muscarinic agonist]] |[[eye drops]] |- |[[timolol]] |[[β-receptor antagonist]] | | *[[bradycardia]] *[[bronchoconstriction]] |- |[[acetazolamide]] |[[carbonic anhydrase inhibitor]] |[[systemic administration]] | *[[diuresis]] *[[loss of appetite]] *tingling *[[neutropenia]] |- |[[clonidine]] |[[α2-receptor agonist]] |eye drops | |- |[[ecothiopate]] |[[cholinesterase inhibitor]] |eye drops | *[[muscle spasm]] *[[systemic effect]] |- |[[carteolol]] |[[β-receptor antagonist]] |eye drops | *[[bradycardia]] *[[bronchoconstriction]] |- |[[dorzolamide]] |[[carbonic anhydrase inhibitor]] |eye drops | *bitter taste *burning sensation |- |[[apraclonidine]] |[[α-2 agonist]] |eye drops | |- |[[latanoprost]] |[[prostaglandin]] analogue | | *[[ocular pigmentation]] |- |} ==References== {{reflist|2}} ==External links== *[http://www.emedicine.com/oph/topic578.htm eMedicine - Ocular Hypertension] *[http://www.nei.nih.gov/glaucomaeyedrops/ National Eye Institute] *[http://www.glaucoma-association.com/ International Glaucoma Association] {{eye-stub}} {{Eye pathology}} [[Category:Ophthalmology]] [[pt:Hipertensão ocular]]