Ocular hypertension is intraocular pressure

Intraocular pressure

Intraocular pressure 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 from glaucoma...

 higher than normal in the absence of optic nerve

Optic nerve

The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...

 damage or visual field

Visual field

The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...

 loss.

Current consensus in ophthalmology

Ophthalmology

Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...

 defines normal introcular pressure (IOP) as that between 10 mmHg and 21 mmHg. Elevated IOP is the most important risk factor for glaucoma

Glaucoma

Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

, 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

Intraocular pressure

Intraocular pressure 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 from glaucoma...

 is mainly maintained by the liquid aqueous humor, which is produced by the ciliary body

Ciliary body

The ciliary body is the circumferential tissue inside the eye composed of the ciliary muscle and ciliary processes. It is triangular in horizontal section and is coated by a double layer, the ciliary epithelium. This epithelium produces the aqueous humor. The inner layer is transparent and covers...

 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

Zonule of Zinn

The zonule of Zinn is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye....

. 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.

Medication

Ocular hypertension is mostly treated with pilocarpine

Pilocarpine

Pilocarpine is a parasympathomimetic alkaloid obtained from the leaves of tropical American shrubs from the genus Pilocarpus. It is a non-selective muscarinic receptor agonist in the parasympathetic nervous system, which acts therapeutically at the muscarinic acetylcholine receptor M3 due to its...

, timolol

Timolol

Timolol maleate is a non-selective beta-adrenergic receptor blocker.-Uses:In its oral form , it is used:* to treat high blood pressure* to prevent heart attacks* to prevent migraine headaches...

, acetazolamide

Acetazolamide

Acetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, Idiopathic intracranial hypertension , altitude sickness, cystinuria, and dural ectasia...

 and clonidine

Clonidine

Clonidine is a sympatholytic medication used to treat medical conditions, such as high blood pressure, some pain conditions, ADHD and anxiety/panic disorder...

. There are also other, less commonly used, alternatives, such as medicinal cannabis. Eye drops may initially be started either in one or in both eyes.

Comparison table of ocular antihypertensives

Medication	Mechanism	Dosage form	Adverse effects
pilocarpine Pilocarpine Pilocarpine is a parasympathomimetic alkaloid obtained from the leaves of tropical American shrubs from the genus Pilocarpus. It is a non-selective muscarinic receptor agonist in the parasympathetic nervous system, which acts therapeutically at the muscarinic acetylcholine receptor M3 due to its...	muscarinic agonist	eye drops Eye Drops Eye Drops was a television program on TechTV that showcased short computer animation movies and clips made using off the shelf 3D animation software. The show claimed to showcase all different types of animation, but only a very small number of shorts featured non-CG animation...
timolol Timolol Timolol maleate is a non-selective beta-adrenergic receptor blocker.-Uses:In its oral form , it is used:* to treat high blood pressure* to prevent heart attacks* to prevent migraine headaches...	β-receptor antagonist	eye drops	bradycardia Bradycardia Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart... bronchoconstriction Bronchoconstriction Bronchoconstriction is the constriction of the airways in the lungs due to the tightening of surrounding smooth muscle, with consequent coughing, wheezing, and shortness of breath. Bronchoconstriction can also be due to an accumulation of thick mucus....
acetazolamide Acetazolamide Acetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, Idiopathic intracranial hypertension , altitude sickness, cystinuria, and dural ectasia...	carbonic anhydrase inhibitor	systemic administration Systemic administration Systemic administration is a route of administration that is either:*enteral*parenteral...	diuresis Diuresis Diuresis may refer to:* Urine production, as an aspect of fluid balance* Excessive urine production - see polyuria* Immersion diuresis... loss of appetite tingling neutropenia Neutropenia Neutropenia, from Latin prefix neutro- and Greek suffix -πενία , is a granulocyte disorder characterized by an abnormally low number of neutrophils, the most important type of white blood cell...
clonidine Clonidine Clonidine is a sympatholytic medication used to treat medical conditions, such as high blood pressure, some pain conditions, ADHD and anxiety/panic disorder...	α2-receptor agonist	eye drops
ecothiopate	cholinesterase inhibitor	eye drops	muscle spasm systemic effect
carteolol Carteolol Carteolol is a non-selective beta blocker used to treat glaucoma....	β-receptor antagonist	eye drops	bradycardia Bradycardia Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart... bronchoconstriction Bronchoconstriction Bronchoconstriction is the constriction of the airways in the lungs due to the tightening of surrounding smooth muscle, with consequent coughing, wheezing, and shortness of breath. Bronchoconstriction can also be due to an accumulation of thick mucus....
dorzolamide Dorzolamide Dorzolamide is a carbonic anhydrase inhibitor. It is an anti-glaucoma agent and topically applied in the form of eye drops. This drug, developed by Merck, was the first drug in human therapy which resulted from structure-based drug design...	carbonic anhydrase inhibitor	eye drops	bitter taste burning sensation
apraclonidine Apraclonidine Apraclonidine , also known as Iopidine, is a sympathomimetic used in glaucoma therapy. It is an α2-adrenergic agonist and a weak alpha-1 adrenergic receptor agonist....	α-2 agonist	eye drops
latanoprost Latanoprost Latanoprost ophthalmic solution is a topical medication used for controlling the progression of glaucoma or ocular hypertension by reducing intraocular pressure...	prostaglandin Prostaglandin A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring....  analogue	eye drops	ocular pigmentation
bimatoprost Bimatoprost Bimatoprost is a prostaglandin analog/prodrug used topically to control the progression of glaucoma and in the management of ocular hypertension. It reduces intraocular pressure by increasing the outflow of aqueous fluid from the eyes...	prostaglandin Prostaglandin A prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring....  analogue	eye drops	ocular pigmentation

External links

• eMedicine - Ocular Hypertension
• National Eye Institute
• International Glaucoma Association