Glaucoma
Overview
 
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye(s) and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye (aqueous humour
Aqueous humour
The aqueous humour is a clear, gelatinous fluid similar to plasma, but containing low-protein concentrations. It is secreted from the ciliary epithelium, a structure supporting the lens. It is located in the space between the lens and the cornea...

). The term 'ocular hypertension' is used for cases having constantly raised 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...

 (IOP) without any associated optic nerve damage. Conversely, the term 'normal' or 'low tension glaucoma' is suggested for the typical visual field defects when associated with a normal or low IOP.

The nerve damage involves loss of retinal ganglion cells in a characteristic pattern.
Encyclopedia
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye(s) and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye (aqueous humour
Aqueous humour
The aqueous humour is a clear, gelatinous fluid similar to plasma, but containing low-protein concentrations. It is secreted from the ciliary epithelium, a structure supporting the lens. It is located in the space between the lens and the cornea...

). The term 'ocular hypertension' is used for cases having constantly raised 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...

 (IOP) without any associated optic nerve damage. Conversely, the term 'normal' or 'low tension glaucoma' is suggested for the typical visual field defects when associated with a normal or low IOP.

The nerve damage involves loss of retinal ganglion cells in a characteristic pattern. There are many different subtypes of glaucoma, but they can all be considered a type of optic neuropathy
Optic neuropathy
The optic nerve contains axons of nerve cells that emerge from the retina, leave the eye at the optic disc, and go to the visual cortex where input from the eye is processed into vision. There are 1.2 million optic nerve fibers that derive from the retinal ganglion cells of the inner retina. Optic...

. Raised intraocular pressure is a significant risk factor for developing glaucoma (above 21 mmHg or 2,799.8 Pa). One person may develop nerve damage at a relatively low pressure, while another person may have high eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

 pressure for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the 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...

 and resultant 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, which can progress to blindness
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

.

Glaucoma can be divided roughly into two main categories, "open angle" and "closed angle" glaucoma. Closed angle glaucoma can appear suddenly and is often painful; visual loss can progress quickly, but the discomfort often leads patients to seek medical attention before permanent damage occurs. Open angle, chronic glaucoma tends to progress at a slower rate and patients may not notice they have lost vision until the disease has progressed significantly.

Glaucoma has been nicknamed the "silent thief of sight" because the loss of vision normally occurs gradually over a long period of time, and is often recognized only when the disease is quite advanced. Once lost, this damaged visual field cannot be recovered. Worldwide, it is the second leading cause of blindness after cataracts. It is also the leading cause of blindness among African Americans. Glaucoma affects one in 200 people aged fifty and younger, and one in 10 over the age of eighty. If the condition is detected early enough, it is possible to arrest the development or slow the progression with medical and surgical means.

The word "glaucoma" comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 γλαύκωμα, "opacity of the crystalline lens". (Cataracts and glaucoma were not distinguished until c.1705).

Signs and symptoms

There are two main types of glaucoma: open-angle glaucoma and closed-angle glaucoma.
Open-angle glaucoma accounts for 90% of glaucoma cases in the United States. It is painless and does not have acute attacks. The only signs are gradually progressive visual field loss, and optic nerve changes (increased cup-to-disc ratio
Cup-to-disc ratio
The cup-to-disc ratio is a measurement used in ophthalmology and optometry to assess the progression of glaucoma. The optic disc is the anatomical location of the eye's "blind spot", the area where the optic nerve and blood vessels enter the retina. The optic disc can be flat or it can have a...

 on fundoscopic examination).

Closed-angle glaucoma accounts for less than 10% of glaucoma cases in the United States, but as many as half of glaucoma cases in other nations (particularly Asian countries). About 10% of patients with closed angles present with acute angle closure crises characterized by sudden ocular pain, seeing halos around lights, red eye, very high intraocular pressure (>30 mmHg), nausea and vomiting, sudden decreased vision, and a fixed, mid-dilated pupil. Acute angle closure is an ocular emergency.

Causes

There are several causes for glaucoma. Ocular hypertension (increased pressure within the eye) is the largest risk factor in most glaucomas, but in some populations, only 50% of people with primary open angle glaucoma actually have elevated ocular pressure.

Dietary

There is no clear evidence that vitamin deficiencies cause glaucoma in humans. It follows, then, that oral vitamin supplementation is not a recommended treatment for glaucoma. Caffeine increases 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...

 in those with glaucoma but does not appear to affect normal individuals.

Ethnicity

Many East Asia
East Asia
East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...

n groups are prone to developing angle closure glaucoma due to their shallower anterior chamber depth, with the majority of cases of glaucoma in this population consisting of some form of angle closure.Inuit
Inuit
The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark , Russia and the United States . Inuit means “the people” in the Inuktitut language...

 also have a 20 to 40 times higher risk than Caucasians of developing primary angle closure glaucoma. Women are three times more likely than men to develop acute angle closure glaucoma due to their shallower anterior chambers. Those of African descent are three times more likely to develop primary open angle glaucoma.

Genetics

Various rare congenital/genetic eye malformations are associated with glaucoma. Occasionally, failure of the normal third trimester gestational atrophy of the hyaloid canal
Hyaloid canal
Hyaloid canal is a small transparent canal running through the vitreous body from the optical nerve disc to the lens; in the fetus it contains a prolongation of the central artery of the retina, the hyaloid artery...

 and the tunica vasculosa lentis
Persistent tunica vasculosa lentis
Persistent tunica vasculosa lentis is a congenital ocular anomaly. It is a form of persistent hyperplastic primary vitreous .* It is a developmental disorder of the vitreous.* Usually unilateral and first noticed in the neonatal period....

 is associated with other anomalies. Angle closure induced ocular hypertension
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...

 and glaucomatous optic neuropathy may also occur with these anomalies. and modelled in mice. Primary open angle glaucoma (POAG) has been found to be associated with mutations in genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...

 at several loci
Locus (genetics)
In the fields of genetics and genetic computation, a locus is the specific location of a gene or DNA sequence on a chromosome. A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic map...

. Normal tension glaucoma, which comprises one third of POAG, is associated with genetic mutations. People with a family history of glaucoma have about six percent chance of developing glaucoma.

Other

Other factors can cause glaucoma, known as "secondary glaucomas", including prolonged use of steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...

s (steroid-induced glaucoma); conditions that severely restrict blood flow to the eye, such as severe diabetic retinopathy
Diabetic retinopathy
Diabetic retinopathy is retinopathy caused by complications of diabetes mellitus, which can eventually lead to blindness....

 and central retinal vein occlusion (neovascular glaucoma);ocular trauma
Blast-related ocular trauma
*Blast-related ocular trauma comprises a specialized group of penetrating and blunt force injuries to the eye and its structure caused by the detonation of explosive materials. The incidence of ocular trauma due to blast forces has increased dramatically with the introduction of new explosives...

 (angle recession glaucoma); and uveitis
Uveitis
Uveitis specifically refers to inflammation of the middle layer of the eye, termed the "uvea" but in common usage may refer to any inflammatory process involving the interior of the eye....

 (uveitic glaucoma).

Pathophysiology

The major risk factor for most glaucomas and focus of treatment is increased intraocular pressure
Ocular hypertension
Ocular hypertension is intraocular pressure higher than normal in the absence of optic nerve damage or visual field loss.Current consensus in ophthalmology defines normal introcular pressure as that between 10 mmHg and 21 mmHg...

. 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 a function of production of liquid aqueous humor by the ciliary processes
Ciliary processes
The ciliary processes are formed by the inward folding of the various layers of the choroid, i.e., the choroid proper and the lamina basalis, and are received between corresponding foldings of the suspensory ligament of the lens.-Anatomy:...

 of the eye and its drainage through the trabecular meshwork
Trabecular meshwork
The trabecular meshwork is an area of tissue in the eye located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humor from the eye via the anterior chamber .The tissue is spongy and lined by trabeculocytes; it allows fluid to drain into a set of...

. Aqueous humor flows from the ciliary processes into the posterior chamber
Posterior chamber
The posterior chamber should not be confused with vitreous chamber. The posterior chamber is a narrow chink behind the peripheral part of the iris of the lens, and in front of the suspensory ligament of the lens and the ciliary processes. The Posterior Chamber consists of small space directly...

, bounded posteriorly by the lens
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...

 and the zonules of Zinn and anteriorly by the iris
Iris (anatomy)
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. "Eye color" is the color of the iris, which can be green, blue, or brown. In some cases it can be hazel , grey, violet, or even pink...

. It then flows through the pupil
Pupil
The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In...

 of the iris into the anterior chamber
Anterior chamber
The anterior chamber is the fluid-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Aqueous humor is the fluid that fills the anterior chamber. Hyphema and glaucoma are two main pathologies in this area. In hyphema, blood fills the anterior chamber...

, bounded posteriorly by the iris and anteriorly by the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

. From here the trabecular meshwork drains aqueous humor via Schlemm's canal
Schlemm's canal
Schlemm's canal, also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream via the anterior ciliary veins....

 into scleral plexuses and general blood circulation.

In open angle glaucoma, there is reduced flow through the trabecular meshwork; in angle closure glaucoma, the iridocorneal angle is completely closed because of forward displacement of the final roll and root of the iris against the cornea resulting in the inability of the aqueous fluid to flow from the posterior to the anterior chamber and then out of the trebecular network.

The inconsistent relationship of glaucomatous optic neuropathy with ocular hypertension has provoked hypotheses and studies on anatomic structure, eye development, nerve compression trauma, optic nerve blood flow, excitatory neurotransmitter, trophic factor, retinal ganglion cell/axon degeneration, glial support cell, immune, aging mechanisms of neuron loss, and severing of the nerve fibers at the scleral edge.

Diagnosis

Screening for glaucoma is usually performed as part of a standard eye examination
Eye examination
An eye examination is a battery of tests performed by an ophthalmologist, optometrist, or orthoptist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes....

 performed by ophthalmologists, orthoptists and optometrists. Testing for glaucoma should include measurements of the 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...

 via tonometry
Tonometry
Tonometry is the procedure eye care professionals perform to determine the intraocular pressure , the fluid pressure inside the eye. It is an important test in the evaluation of patients at risk from glaucoma...

, changes in size or shape of the eye, anterior chamber angle examination or gonioscopy
Gonioscopy
Gonioscopy describes the use of a goniolens in conjunction with a slit lamp or operating microscope to gain a view of the iridocorneal angle, or the anatomical angle formed between the eye's cornea and iris...

, and examination of the 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...

 to look for any visible damage to it, or change in the cup-to-disc ratio
Cup-to-disc ratio
The cup-to-disc ratio is a measurement used in ophthalmology and optometry to assess the progression of glaucoma. The optic disc is the anatomical location of the eye's "blind spot", the area where the optic nerve and blood vessels enter the retina. The optic disc can be flat or it can have a...

 and also rim appearance and vascular change. A formal visual field test
Perimetry
Perimetry or campimetry is the systematic measurement of differential light sensitivity in the visual field by the detection of the presence of test targets on a defined background. Visual field testing can be performed clinically with confrontational field testing keeping the subject's gaze fixed...

 should be performed. The retinal nerve fiber layer can be assessed with imaging techniques such as optical coherence tomography
Optical coherence tomography
Optical coherence tomography is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media . Optical coherence tomography is an interferometric technique, typically employing near-infrared light...

 (OCT), scanning laser polarimetry
Scanning laser polarimetry
Scanning laser polarimetry is the use of polarised light to measure the thickness of the retinal nerve fiber layer as part of a glaucoma workup. The GDx-VCC is one example....

 (GDx), and/or scanning laser ophthalmoscopy
Scanning laser ophthalmoscopy
Scanning laser ophthalmoscopy is a method of examination of the eye. It uses the technique of confocal laser scanning microscopy for diagnostic imaging of retina or cornea of the human eye....

, also known as Heidelberg retina tomography (HRT3).

Owing to the sensitivity of all methods of tonometry to corneal thickness, methods such as Goldmann tonometry
Tonometry
Tonometry is the procedure eye care professionals perform to determine the intraocular pressure , the fluid pressure inside the eye. It is an important test in the evaluation of patients at risk from glaucoma...

 should be augmented with pachymetry to measure central corneal thickness (CCT). A thicker-than-average cornea can result in a pressure reading higher than the 'true' pressure, whereas a thinner-than-average cornea can produce a pressure reading lower than the 'true' pressure.

Because pressure measurement error can be caused by more than just CCT (i.e., corneal hydration, elastic properties, etc.), it is impossible to 'adjust' pressure measurements based only on CCT measurements. The Frequency Doubling Illusion
Frequency Doubling Illusion
The Frequency-Doubling Illusion is an apparent doubling of spatial frequency when a sinusoidal grating is modulated rapidly in temporal counterphase. Recently, it has been proposed that the illusion arises from a spatially nonlinear ganglion cell class...

 can also be used to detect glaucoma with the use of a frequency doubling technology (FDT) perimeter.

Examination for glaucoma also could be assessed with more attention given to sex, race, history of drug use, refraction, inheritance and family history.

Screening

Those at risk are advised to have a dilated eye examination
Dilated fundus examination
Dilated fundus examination is a diagnostic procedure that employs the use of mydriatic eye drops to dilate or enlarge the pupil in order to obtain a better view of the fundus of the eye. Once the pupil is dilated, examiners often use specialized equipment such as an ophthalmoscope or fundus...

 at least once a year.

Management

The modern goals of glaucoma management are to avoid glaucomatous damage and nerve damage, and preserve visual field and total quality of life for patients with minimal side effects. This requires appropriate diagnostic techniques and follow-up examinations and judicious selection of treatments for the individual patient. Although intraocular pressure is only one of the major risk factors for glaucoma, lowering it via various pharmaceuticals and/or surgical techniques is currently the mainstay of glaucoma treatment.

Vascular flow and neurodegenerative theories of glaucomatous optic neuropathy have prompted studies on various neuroprotective therapeutic strategies, including nutritional compounds, some of which may be regarded by clinicians as safe for use now, while others are on trial.

Medication

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...

 can be lowered with medication, usually eye drops. Several different classes of medications are used to treat glaucoma, with several different medications in each class.

Each of these medicines may have local and systemic side effects. Adherence to medication protocol can be confusing and expensive; if side effects occur, the patient must be willing either to tolerate these, or to communicate with the treating physician to improve the drug regimen. Initially, glaucoma drops may reasonably be started in either one or in both eyes.

Poor compliance with medications and follow-up visits is a major reason for vision loss in glaucoma patients. A 2003 study of patients in an HMO found that half failed to fill their prescriptions the first time, and one-fourth failed to refill their prescriptions a second time. Patient education and communication must be ongoing to sustain successful treatment plans for this lifelong disease with no early symptoms.

The possible neuroprotective effects of various topical and systemic medications are also being investigated.
  • Prostaglandin analogs, such as latanoprost
    Latanoprost
    Latanoprost ophthalmic solution is a topical medication used for controlling the progression of glaucoma or ocular hypertension by reducing intraocular pressure...

     (Xalatan), 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...

     (Lumigan) and travoprost
    Travoprost
    Travoprost ophthalmic solution is a topical medication used for controlling the progression of glaucoma or ocular hypertension, by reducing intraocular pressure. It is a synthetic prostaglandin analog that works by increasing the outflow of aqueous fluid from the eyes...

     (Travatan), increase uveoscleral outflow of aqueous humor. Bimatoprost also increases trabecular outflow.
  • Topical beta-adrenergic receptor antagonists, such as 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...

    , levobunolol
    Levobunolol
    Levobunolol is a non-selective beta blocker. It is used topically to manage glaucoma....

     (Betagan), and betaxolol
    Betaxolol
    Betaxolol is a selective beta1 receptor blocker used in the treatment of hypertension and glaucoma. Being selective for beta1 receptors, it typically has fewer systemic side effects than non-selective beta-blockers, for example, not causing bronchospasm as timolol may...

    , decrease aqueous humor production 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...

    .
  • Alpha2-adrenergic agonists, such as brimonidine
    Brimonidine
    Brimonidine is a drug used to treat open-angle glaucoma or ocular hypertension.It acts via decreasing synthesis of aqueous humor, and increasing the amount that drains from the eye through uveoscleral outflow.As a treatment for glaucoma, it is usually given in eyedrop form.Brimonidine is an...

     (Alphagan) and 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....

    , work by a dual mechanism, decreasing aqueous humor production and increasing trabecular outflow.
  • Less-selective alpha agonist
    Alpha agonist
    Alpha agonist may refer to:* Alpha-adrenergic agonist, drugs that selectively stimulate alpha adrenergic receptors* PPAR modulator, drugs which act upon the Peroxisome proliferator-activated receptor alpha...

    s, such as epinephrine
    Epinephrine
    Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

    , decrease aqueous humor production through vasoconstriction of ciliary body blood vessels. Epinephrine's mydriatic effect, however, renders it unsuitable for closed angle glaucoma.
  • Miotic agents (parasympathomimetics), such as 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...

    , work by contraction of the ciliary muscle, tightening the trabecular meshwork
    Trabecular meshwork
    The trabecular meshwork is an area of tissue in the eye located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humor from the eye via the anterior chamber .The tissue is spongy and lined by trabeculocytes; it allows fluid to drain into a set of...

     and allowing increased outflow of the aqueous humour. Ecothiopate is used in chronic glaucoma.
  • Carbonic anhydrase inhibitors
    Carbonic anhydrase inhibitors
    Carbonic anhydrase inhibitors are a class of pharmaceuticals that suppress the activity of carbonic anhydrase. Their clinical use has been established as antiglaucoma agents, diuretics, antiepileptics, in the management of mountain sickness, gastric and duodenal ulcers, neurological disorders, or...

    , such as 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...

     (Trusopt), brinzolamide
    Brinzolamide
    Brinzolamide is a carbonic anhydrase inhibitor used to lower intraocular pressure in patients with open-angle glaucoma or ocular hypertension.- Chemistry :...

     (Azopt), and 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...

     (Diamox), lower secretion of aqueous humor by inhibiting carbonic anhydrase in the ciliary body.
  • Physostigmine
    Physostigmine
    Physostigmine is a parasympathomimetic alkaloid, specifically, a reversible cholinesterase inhibitor. It occurs naturally in the Calabar bean....

     is also used to treat glaucoma and delayed gastric emptying.
  • Marijuana (cannabis
    Cannabis
    Cannabis is a genus of flowering plants that includes three putative species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for seed and seed oils, for medicinal purposes, and as a...

    ), when smoked or eaten, reduced intraocular pressure by about 25% in several studies, a reduction as good as that obtained by most other medicines. The effect lasts three to four hours.

Surgery

Both laser
Laser surgery
Laser surgery is surgery using a laser to cut tissue instead of a scalpel. Examples include the use of a laser scalpel in otherwise conventional surgery, and soft tissue laser surgery, in which the laser beam vaporizes soft tissue with high water content...

 and conventional surgeries are performed to treat glaucoma.

Surgery is the primary therapy for those with congenital glaucoma.

Generally, these operations are a temporary solution, as there is not yet a cure for glaucoma.

Canaloplasty

Canaloplasty is a nonpenetrating procedure using microcatheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...

 technology. To perform a canaloplasty, an incision is made into the eye to gain access to Schlemm's canal
Schlemm's canal
Schlemm's canal, also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream via the anterior ciliary veins....

 in a similar fashion to a viscocanalostomy. A microcatheter will circumnavigate the canal around the iris, enlarging the main drainage channel and its smaller collector channels through the injection of a sterile, gel-like material called viscoelastic. The catheter is then removed and a suture is placed within the canal and tightened.

By opening the canal, the pressure inside the eye may be relieved, although the reason is unclear, since the canal (of Schlemm) does not have any significant fluid resistance in glaucoma or healthy eyes. Long-term results are not available.

Laser surgery

Laser trabeculoplasty may be used to treat open angle glaucoma. It is a temporary solution, not a cure. An 50 μm argon laser spot is aimed at the trabecular meshwork to stimulate opening of the mesh to allow more outflow of aqueous fluid. Usually, half of the angle is treated at a time. Traditional laser trabeculoplasty uses a thermal argon laser in a procedure called argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

 laser trabeculoplasty (ALT).

A newer type of laser trabeculoplasty uses a "cold" (nonthermal) laser to stimulate drainage in the trabecular meshwork. This newer procedure, selective laser trabeculoplasty (SLT) uses a 532 nm frequency-doubled, Q-switched Nd:YAG laser
Nd:YAG laser
Nd:YAG is a crystal that is used as a lasing medium for solid-state lasers. The dopant, triply ionized neodymium, typically replaces yttrium in the crystal structure of the yttrium aluminium garnet , since they are of similar size...

, which selectively targets melanin pigment in the trabecular meshwork cells. Studies show SLT is as effective as ALT at lowering eye pressure. In addition, SLT may be repeated three to four times, whereas ALT can usually be repeated only once.

Nd:YAG laser peripheral iridotomy (LPI) may be used in patients susceptible to or affected by angle closure glaucoma or pigment dispersion syndrome
Pigment dispersion syndrome
Pigment dispersion syndrome is an affliction of the eye that can lead to a form of glaucoma known as pigmentary glaucoma. It takes place when pigment cells slough off from the back of the iris and float around in the aqueous humor...

. During laser iridotomy, laser energy is used to make a small, full-thickness opening in the iris to equalize the pressure between the front and back of the iris, thus correcting any abnormal bulging of the iris. In people with narrow angles, this can uncover the trabecular meshwork. In some cases of intermittent or short-term angle closure, this may lower the eye pressure. Laser iridotomy reduces the risk of developing an attack of acute angle closure. In most cases, it also reduces the risk of developing chronic angle closure or of adhesions of the iris to the trabecular meshwork.

Diode laser cycloablation lowers IOP by reducing aqueous secretion by destroying secretory ciliary epithelium.

Trabeculectomy

The most common conventional surgery performed for glaucoma is the trabeculectomy
Trabeculectomy
Trabeculectomy is a surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye's trabecular meshwork and adjacent structures. It is the most common glaucoma surgery performed and allows drainage of aqueous humor from within the eye to underneath...

. Here, a partial thickness flap is made in the scleral wall of the eye, and a window opening is made under the flap to remove a portion of the trabecular meshwork. The scleral flap is then sutured loosely back in place to allow fluid to flow out of the eye through this opening, resulting in lowered intraocular pressure and the formation of a bleb or fluid bubble on the surface of the eye. Scarring can occur around or over the flap opening, causing it to become less effective or lose effectiveness altogether. Traditionally, chemotherapeutic adjuncts, such as mitomycin C (MMC, 0.5-0.2 mg/ml) or 5-fluorouracil (5-FU, 50 mg/ml), are applied with soaked sponges on wound bed to prevent filtering blebs from scarring by inhibiting fibroblast proliferation. Contemporary alternatives include the sole or combinative implementation of non-chemotherapeutic adjuncts, such as collagen matrix implant or other biodegradable spacers, to prevent super scarring by randomization and modulation of fibroblast proliferation in addition to the mechanical prevention of wound contraction and adhesion.

Glaucoma drainage implants

Several different glaucoma drainage implants include the original Molteno implant (1966), the Baerveldt tube shunt, or the valved implants, such as the Ahmed glaucoma valve implant or the ExPress Mini Shunt and the later generation pressure ridge Molteno implants. These are indicated for glaucoma patients not responding to maximal medical therapy, with previous failed guarded filtering surgery (trabeculectomy). The flow tube is inserted into the anterior chamber of the eye, and the plate is implanted underneath the conjunctiva to allow flow of aqueous fluid out of the eye into a chamber called a bleb
Bleb
Bleb may refer to:* Bleb , an irregular bulge in the plasma membrane of a cell* Bleb , a large blister filled with serous fluid* Bleb , a small bubble-like inclusion of one mineral within a larger mineral...

.
  • The first-generation Molteno and other nonvalved implants sometimes require the ligation of the tube until the bleb formed is mildly fibrosed and water-tight. This is done to reduce postoperative hypotony—sudden drops in postoperative intraocular pressure (IOP).
  • Valved implants, such as the Ahmed glaucoma valve, attempt to control postoperative hypotony by using a mechanical valve.


The ongoing scarring over the conjunctival dissipation segment of the shunt may become too thick for the aqueous humor to filter through. This may require preventive measures using antifibrotic medications, such as 5-fluorouracil or mitomycin-C (during the procedure), or other non-antifibrotic medication methods, such as collagen matrix implant, biodegradable spacer, or additional surgery. And for glaucomatous painful blind eye and some cases of glaucoma, cyclocryotherapy for ciliary body ablation could be considered to be performed.

Veterinary implant

TR BioSurgical has commercialized a new implant specifically for veterinary medicine, called TR-ClarifEYE. The implant consists of a new biomaterial, the STAR BioMaterial, which consists of silicone with a very precise homogenous pore size, a property which reduces fibrosis
Fibrosis
Fibrosis is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process. This is as opposed to formation of fibrous tissue as a normal constituent of an organ or tissue...

 and improves tissue integration. The implant contains no valves and is placed completely within the eye without sutures. To date, it has demonstrated long-term success (> 1yr) in a pilot study in medically refractory dogs with advanced glaucoma.

Laser-assisted nonpenetrating deep sclerectomy

The most common surgical approach currently used for the treatment of glaucoma is trabeculectomy, in which the sclera is punctured to alleviate intraocular pressure.

Nonpenetrating deep sclerectomy (NPDS) surgery is a similar, but modified, procedure, in which instead of puncturing the scleral wall, a patch of the sclera is skimmed to a level, upon which, percolation of liquid from the inner eye is achieved and thus alleviating IOP, without penetrating the eye. NPDS is demonstrated to cause significantly less side effects than trabeculectomy. However, NPDS is performed manually and requires great skill to achieve a lengthy learning curve.

Laser-assisted NPDS is the performance of NPDS with the use of a CO2 laser system. The laser-based system is self-terminating once the required scleral thickness and adequate drainage of the intraocular fluid have been achieved. This self-regulation effect is achieved as the CO2 laser essentially stops ablating as soon as it comes in contact with the intraocular percolated liquid, which occurs as soon as the laser reaches the optimal residual intact layer thickness.

Epidemiology

Research

  • Advanced Glaucoma Intervention Study (AGIS) is a large American National Eye Institute-sponsored study designed "to assess the long-range outcomes of sequences of interventions involving trabeculectomy and argon laser trabeculoplasty in eyes that have failed initial medical treatment for glaucoma". It recommends different treatments based on race.
  • Early Manifest Glaucoma Trial (EMGT) is another NEI study that found immediate treatment of people who have early stage glaucoma can delay progression of the disease.
  • Ocular Hypertension Treatment Study (OHTS), also an NEI study, found topical ocular hypotensive medication was effective in delaying or preventing onset of primary open angle glaucoma (POAG) in individuals with elevated intraocular pressure. Although this does not imply that all patients with borderline or elevated IOP should receive medication, clinicians should consider initiating treatment for individuals with ocular hypertension who are at moderate or high risk for developing POAG.
  • The Blue Mountains Eye Study was the first large, population-based assessment of visual impairment and common eye diseases of a representative older Australian community sample. Risk factors for glaucoma and other eye disease were determined.


Natural compounds
Natural compounds of research interest in glaucoma prevention or treatment include: fish oil
Fish oil
Fish oil is oil derived from the tissues of oily fish. Fish oils contain the omega-3 fatty acids eicosapentaenoic acid , and docosahexaenoic acid , precursors of certain eicosanoids that are known to reduce inflammation throughout the body, and are thought to have many health benefits.Fish do not...

 and omega 3 fatty acids, alpha lipoic acid, bilberries, vitamin E
Vitamin E
Vitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...

, cannabinoids
Cannabinoids
Cannabinoids are a class of chemical compounds that include the phytocannabinoids , and chemical compounds that mimic the actions of phytocannabinoids or have a similar structure...

, carnitine
Carnitine
Carnitine is a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine. In living cells, it is required for the transport of fatty acids from the cytosol into the mitochondria during the breakdown of lipids for the generation of metabolic energy. It is widely...

, coenzyme Q10, curcurmin
Turmeric
Turmeric is a rhizomatous herbaceous perennial plant of the ginger family, Zingiberaceae. It is native to tropical South Asia and needs temperatures between 20 °C and 30 °C and a considerable amount of annual rainfall to thrive...

, Salvia miltiorrhiza
Salvia miltiorrhiza
Salvia miltiorrhiza , also known as red sage, Chinese sage, tan shen, or danshen, is a perennial plant in the genus Salvia, highly valued for its roots in traditional Chinese medicine. Native to China and Japan, it grows at elevation, preferring grassy places in forests, hillsides, and along...

, dark chocolate
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...

, erythropoietin
Erythropoietin
Erythropoietin, or its alternatives erythropoetin or erthropoyetin or EPO, is a glycoprotein hormone that controls erythropoiesis, or red blood cell production...

, folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...

, Ginkgo biloba, ginseng
Ginseng
Ginseng is any one of eleven species of slow-growing perennial plants with fleshy roots, belonging to the genus Panax of the family Araliaceae....

, L-glutathione
Glutathione
Glutathione is a tripeptide that contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side-chain...

, grape seed
Grape
A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

 extract, green tea
Green tea
Green tea is made solely from the leaves of Camellia sinensis that have undergone minimal oxidation during processing. Green tea originates from China and has become associated with many cultures throughout Asia. It has recently become more widespread in the West, where black tea is traditionally...

, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

, melatonin
Melatonin
Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...

, methylcobalamin, N-acetyl-L cysteine, pycnogenols, resveratrol
Resveratrol
Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....

, quercetin
Quercetin
Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...

 and salt
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

. However, most of these compounds have not demonstrated effectiveness in clinical trials. Magnesium, ginkgo, salt and fludrocortisone
Fludrocortisone
Fludrocortisone is a synthetic corticosteroid with moderate glucocorticoid potency and much greater mineralocorticoid potency. The brand name in the U.S. and Canada is Florinef.-Uses:...

, are already used by some physicians.

Cannabis
Studies in the 1970s showed marijuana, when smoked or eaten, effectively lowers intraocular pressure by about 25%, as much as standard medications. In an effort to determine whether marijuana, or drugs derived from marijuana, might be effective as a glaucoma treatment, the US National Eye Institute supported research studies from 1978 to 1984. These studies demonstrated some derivatives of marijuana lowered intraocular pressure when administered orally, intravenously, or by smoking, but not when topically applied to the eye.

In 2003, the American Academy of Ophthalmology
American Academy of Ophthalmology
The American Academy of Ophthalmology is the largest national membership medical association of ophthalmologists–medical doctors specializing in eye care and surgery including medical, surgical and optical care. More than 90 percent of practicing U.S. Eye M.D.s are Academy members, and the...

 released a position statement which said "studies demonstrated that some derivatives of marijuana did result in lowering of IOP when administered orally, intravenously, or by smoking, but not when topically applied to the eye. The duration of the pressure-lowering effect is reported to be in the range of 3 to 4 hours".

However, the position paper qualified that by stating marijuana was not more effective than prescription medications, and "no scientific evidence has been found that demonstrates increased benefits and/or diminished risks of marijuana use to treat glaucoma compared with the wide variety of pharmaceutical agents now available."

The first patient in the United States federal government's Compassionate Investigational New Drug program
Compassionate Investigational New Drug program
The Compassionate Investigational New Drug program, or Compassionate IND, is a United States Federal Government-ran Investigational New Drug program that allows a limited number of patients to use medical marijuana grown at the University of Mississippi. It is administered by the National...

, Robert Randall, was afflicted with glaucoma and had successfully fought charges of marijuana cultivation because it was deemed a medical necessity
Medical necessity
Medical necessity is a United States legal doctrine, related to activities which may be justified as reasonable, necessary, and/or appropriate, based on evidence-based clinical standards of care. Other countries may have medical doctrines or legal rules covering broadly similar grounds...

 (U.S. v. Randall) in 1976.

5-HT2A agonists
Peripherally selective 5-HT2A
5-HT2A receptor
The mammalian 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor . This is the main excitatory receptor subtype among the GPCRs for serotonin , although 5-HT2A may also have an inhibitory effect on certain areas such...

 agonist
Agonist
An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance...

s, such as the indazole derivative AL-34662
AL-34662
AL-34662 is an indazole derivative drug that is being developed for the treatment of glaucoma. It acts as a selective 5-HT2A receptor agonist, the same target as that of hallucinogenic drugs like psilocin, but unlike these drugs, AL-34662 was designed specifically as a peripherally selective drug,...

, are currently under development and show significant promise in the treatment of glaucoma.

Implanted sensor

The world's smallest computer system, one square mm in size, has been developed by researchers at the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...

, and is designed to be implanted in a person's eye as a pressure monitor to continuously track the progress of glaucoma. The processor consists of an ultra-low-power microprocessor, a pressure sensor, memory, a thin-film battery, a solar cell and a wireless radio with an antenna that can transmit data to an external reader device.

ES cell

The survey team of Dr.Yoshiki Sasai, working at the RIKEN
RIKEN
is a large natural sciences research institute in Japan. Founded in 1917, it now has approximately 3000 scientists on seven campuses across Japan, the main one in Wako, just outside Tokyo...

 of Center for Developmental Biology (CDB) in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, succeeded in making a retina cell in three dimension from embryonic stem cells in Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

 (7th April 2011). It was the first success in the world, and he said the schedule putting it to practical use into retinas of human and clinical application within 2 years.

Primary glaucoma and its variants (H40.1-H40.2)

Primary glaucoma
  • Primary angle-closure glaucoma, also known as primary closed-angle glaucoma, narrow-angle glaucoma, pupil-block glaucoma, acute congestive glaucoma
  • Acute angle-closure glaucoma
  • Chronic angle-closure glaucoma
  • Intermittent angle-closure glaucoma
  • Superimposed on chronic open-angle closure glaucoma ("combined mechanism" - uncommon)
  • Primary open-angle glaucoma, also known as chronic open-angle glaucoma, chronic simple glaucoma, glaucoma simplex
  • High-tension glaucoma
  • Low-tension glaucoma

Variants of primary glaucoma
  • Pigmentary glaucoma
  • Exfoliation glaucoma, also known as pseudoexfoliative glaucoma or glaucoma capsulare


Primary angle-closure glaucoma is caused by contact between the iris and trabecular meshwork, which in turn obstructs outflow of the aqueous humor from the eye. This contact between iris and trabecular meshwork (TM) may gradually damage the function of the meshwork until it fails to keep pace with aqueous production, and the pressure rises. In over half of all cases, prolonged contact between iris and TM causes the formation of synechiae (effectively "scars").

These cause permanent obstruction of aqueous outflow. In some cases, pressure may rapidly build up in the eye, causing pain and redness (symptomatic, or so called "acute" angle-closure). In this situation, the vision may become blurred, and halos may be seen around bright lights. Accompanying symptoms may include headache and vomiting.

Diagnosis is made from physical signs and symptoms: pupils mid-dilated and unresponsive to light, cornea edematous (cloudy), reduced vision, redness, and pain. However, the majority of cases are asymptomatic. Prior to very severe loss of vision, these cases can only be identified by examination, generally by an eye care professional.

Once any symptoms have been controlled, the first line (and often definitive) treatment is laser iridotomy. This may be performed using either Nd:YAG or argon lasers, or in some cases by conventional incisional surgery. The goal of treatment is to reverse, and prevent, contact between iris and trabecular meshwork. In early to moderately advanced cases, iridotomy is successful in opening the angle in around 75% of cases. In the other 25%, laser iridoplasty, medication (pilocarpine) or incisional surgery may be required.

Primary open-angle glaucoma is when optic nerve damage results in a progressive loss of the visual field. This is associated with increased pressure in the eye. Not all people with primary open-angle glaucoma have eye pressure that is elevated beyond normal, but decreasing the eye pressure further has been shown to stop progression even in these cases.

The increased pressure is caused by trabecular blockage which is where the aqueous humor in the eye drains out. Because the microscopic passageways are blocked, the pressure builds up in the eye and causes imperceptible very gradual vision loss. Peripheral vision is affected first, but eventually the entire vision will be lost if not treated.

Diagnosis is made by looking for cupping of the optic nerve. Prostaglandin agonists work by opening uveoscleral passageways. Beta blockers, such as timolol, work by decreasing aqueous formation. Carbonic anhydrase inhibitors decrease bicarbonate formation from ciliary processes in the eye, thus decreasing formation of Aqueous humor. Parasympathetic analogs are drugs that work on the trabecular outflow by opening up the passageway and constricting the pupil. Alpha 2 agonists (brimonidine
Brimonidine
Brimonidine is a drug used to treat open-angle glaucoma or ocular hypertension.It acts via decreasing synthesis of aqueous humor, and increasing the amount that drains from the eye through uveoscleral outflow.As a treatment for glaucoma, it is usually given in eyedrop form.Brimonidine is an...

, 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....

) both decrease fluid production (via. inhibition of AC) and increase drainage.

Developmental glaucoma (Q15.0)

Developmental glaucoma
  • Primary congenital glaucoma
  • Infantile glaucoma
  • Glaucoma associated with hereditary of familial diseases

Secondary glaucoma (H40.3-H40.6)

Secondary glaucoma
  • Inflammatory glaucoma
  • Uveitis of all types
  • Fuchs heterochromic iridocyclitis
  • Phacogenic glaucoma
  • Angle-closure glaucoma with mature cataract
  • Phacoanaphylactic glaucoma secondary to rupture of lens capsule
  • Phacolytic glaucoma due to phacotoxic meshwork blockage
  • Subluxation of lens
  • Glaucoma secondary to intraocular hemorrhage
  • Hyphema
  • Hemolytic glaucoma, also known as erythroclastic glaucoma
  • Traumatic glaucoma
  • Angle recession glaucoma: Traumatic recession on anterior chamber angle
  • Postsurgical glaucoma
  • Aphakic pupillary block
  • Ciliary block glaucoma
    • Neovascular glaucoma (see below for more details)
    • Drug-induced glaucoma
    • Corticosteroid induced glaucoma
    • Alpha-chymotrypsin glaucoma. Postoperative ocular hypertension from use of alpha chymotrypsin.
    • Glaucoma of miscellaneous origin
    • Associated with intraocular tumors
    • Associated with retinal detachments
    • Secondary to severe chemical burns of the eye
    • Associated with essential iris atrophy
    • Toxic glaucoma


Neovascular glaucoma, an uncommon type of glaucoma, is difficult or nearly impossible to treat, and is often caused by proliferative diabetic retinopathy
Diabetic retinopathy
Diabetic retinopathy is retinopathy caused by complications of diabetes mellitus, which can eventually lead to blindness....

 (PDR) or central retinal vein occlusion
Central retinal vein occlusion
The central retinal vein is the venous equivalent of the central retinal artery, and like that blood vessel can suffer from occlusion , similar to that seen in ocular ischemic syndrome...

 (CRVO). It may also be triggered by other conditions that result in ischemia
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...

 of the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

 or 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...

. Individuals with poor blood flow to the eye are highly at risk for this condition.

Neovascular glaucoma results when new, abnormal vessels begin developing in the angle of the eye that begin blocking the drainage. Patients with such condition begin to rapidly lose their eyesight. Sometimes, the disease appears very rapidly, especially after cataract surgery procedures. A new treatment for this disease, as first reported by Kahook and colleagues, involves use of a novel group of medications known as anti-VEGF agents. These injectable medications can lead to a dramatic decrease in new vessel formation and, if injected early enough in the disease process, may lead to normalization of intraocular pressure.

Toxic glaucoma is open angle glaucoma with an unexplained significant rise of 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...

 following unknown pathogenesis. Intraocular pressure can sometimes reach 80 mmHg (10,665.8 Pa). It characteristically manifests as 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...

 inflammation and massive trabecular oedema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...

 that sometimes extends to Schlemm's canal
Schlemm's canal
Schlemm's canal, also known as canal of Schlemm or the scleral venous sinus, is a circular channel in the eye that collects aqueous humor from the anterior chamber and delivers it into the bloodstream via the anterior ciliary veins....

. This condition is differentiated from malignant glaucoma by the presence of a deep and clear anterior chamber and a lack of aqueous misdirection. Also, the corneal appearance is not as hazy. A reduction in visual acuity can occur followed neuroretinal breakdown.

Associated factors include inflammation, drugs, trauma and intraocular surgery, including cataract surgery and vitrectomy procedures. Gede Pardianto (2005) reported on four patients who had toxic glaucoma. One of them underwent phaecoemulsification with small particle nucleus drops. Some cases can be resolved with some medication, vitrectomy procedures or trabeculectomy. Valving procedures can give some relief, but further research is required.

Absolute glaucoma (H44.5)

Absolute glaucoma is the end stage of all types of glaucoma. The eye has no vision, absence of pupillary light reflex and pupillary response
Pupillary response
Pupillary response or dilation of the pupil is a physiological response that varies the size of the pupil of the eye via the iris dilator muscle...

, and has a stony appearance. Severe pain is present in the eye. The treatment of absolute glaucoma is a destructive procedure like cyclocryoapplication, cyclophotocoagulation, or injection of 100% alcohol.

External links

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