HOME WEB NEWS IMAGES CLASSIFIEDS YELLOW PAGESPOLLS - SURVEYS WIKI COUNTRIES PHOTOS US UK INDIA
Cities Stocks Weather Movies Coupons Travel Blogs Health Horoscope Maps ASIA EUROPE Classifieds Yellow Pages
 Services and Information at SANDANDGRAVELIWORLD.COMsand gravel wholesale - Shopping, Services and Information at SANDANDGRAVELIWORLD.COM Boston sand and gravel, miles sand and gravel | ||
|
shopping mall, real estate, field theory mal, online, victoria | ||
|
boys apparel, boys clothes, boys clothing store online shopping from a great selection of apparel | ||
 1
|
| Glaucoma Classification & external resources | |
|
| |
|---|---|
| The pink rim of disc contains nerve fibers. The white cup is a pit with no nerve fibers. As glaucoma advances, the cup enlarges until it occupies most of the disc area. Courtesy AgingEye Times | |
| ICD-10 | H40.-H42. |
| ICD-9 | 365 |
| DiseasesDB | 5226 |
| eMedicine | oph/578 |
| MeSH | D005901 |
Human eye cross-sectional view. Courtesy NIH National Eye Institute
Glaucoma is a group of diseases of the optic nerve involving loss of retinal ganglion cells in a characteristic pattern of optic neuropathy. Although raised intraocular pressure is a significant risk factor for developing glaucoma, there is no set threshold for intraocular pressure that causes glaucoma. One person may develop nerve damage at a relatively low pressure, while another person may have high eye pressure for years and yet never develop damage. Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness.
Glaucoma has been nicknamed "sneak thief of sight" because the loss of visual field often occurs gradually over a long time and may only be recognised when it is already quite advanced. Once lost, this damaged visual field can never be recovered. Worldwide, it is the second leading cause of blindness."Glaucoma, Normal Tension, Susceptibility To." OMIM - Online Mendelian Inheritance in Man. Accessed October 17, 2006. Glaucoma affects one in two hundred people aged fifty and younger, and one in ten over the age of eighty.
Contents |
A normal range of vision. Courtesy NIH National Eye Institute
The same view with advanced vision loss from glaucoma.
People with a family history of glaucoma have about a six percent chance of developing glaucoma. Diabetics and those of African descent are three times more likely to develop primary open angle glaucoma. Asians are prone to develop angle-closure glaucoma, and Inuit have a twenty to forty 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. Use of steroids can also cause glaucoma.
There is increasing evidence of ocular blood flow to be involved in the pathogenesis of glaucoma. Current data indicate that fluctuations in blood flow are more harmful in glaucomatous optic neuropathy than steady reductions. Unstable blood pressure and dips are linked to optic nerve head damage and correlate with visual field deterioration.
A number of studies also suggest that there is a correlation, not necessarily causal, between glaucoma and systemic hypertension (i.e. high blood pressure). In normal tension glaucoma, nocturnal hypotension may play a significant role. On the other hand there is no clear evidence that vitamin deficiencies cause glaucoma in humans, nor that oral vitamin supplementation is useful in glaucoma treatment (Surv Ophthalmol 46:43-55, 2001).
Those at risk for glaucoma are advised to have a dilated eye examination at least once a year.National Institutes of Health
Screening for glaucoma is usually performed as part of a standard eye examination performed by ophthalmologists and optometrists. Testing for glaucoma should include measurements of the intraocular pressure via tonometry, changes in size or shape of the eye, and an examination of the optic nerve to look for any visible damage to it, or change in the cup-to-disc ratio. If there is any suspicion of damage to the optic nerve, a formal visual field test should be performed. Scanning laser ophthalmoscopy may also be performed.
Owing to the sensitivity of some methods of tonometry to corneal thickness, methods such as Goldmann tonometry should be augmented with pachymetry to measure the cornea thickness. While a thicker-than-average cornea can cause a false-positive warning for glaucoma risk, a thinner-than-average cornea can produce a false-negative result. A false-positive result is safe, since the actual glaucoma condition will be diagnosed in follow-up tests. A false-negative is not safe, as it may suggest to the practitioner that the risk is low and no follow-up tests will be done.
Although intraocular pressure is only one major risk factors of glaucoma, lowering it via pharmaceuticals or surgery is currently the mainstay of glaucoma treatment. In Europe, Japan, and Canada laser treatment is often the first line of therapy. In the U.S., adoption of early laser has lagged, even though prospective, multi-centered, peer-reviewed studies, since the early \'90s, have shown laser to be at least as effective as topical medications in controlling intraocular pressure and preserving visual field.
Vascular flow and neurodegenerative theories of glaucomatous optic neuropathy have prompted studies on various therapeutic interventions including nutritional compounds some of which may be regarded by clinicians as safe for use now, others are on trial.
Intraocular pressure can be lowered with medication, usually eye drops. There are several different classes of medications 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.[ http://www.biomedcentral.com/1471-2415/7/17 Interpretation of uniocular and binocular trials of glaucoma medications]
Poor compliance with medications and follow-up visits is a major reason for vision loss in glaucoma patients. 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.Ritch R. Natural compounds: evidence for a protective role in eye disease. Can J Ophthalmol. 2007 Jun;42(3):425-38.PMID 17508040 Tsai JC, Song BJ, Wu L, Forbes M. Erythropoietin: a candidate neuroprotective agent in the treatment of glaucoma. J Glaucoma. 2007 Sep;16(6):567-71. PMID 17873720 Mozaffarieh M, Flammer J. Is there more to glaucoma treatment than lowering IOP? Surv Ophthalmol. 2007 Nov;52 Suppl 2:S174-9. PMID 17998043
Natural compounds of research interest in glaucoma prevention or treatment include: fish oil and omega 3 fatty acids, bilberries, vitamin E, cannabinoids, carnitine, coenzyme Q10, curcurmin, Salvia miltiorrhiza, dark chocolate, erythropoietin, folic acid, Ginkgo biloba, Ginseng, L-glutathione, grape seed extract, green tea, magnesium, melatonin, methylcobalamin, N-acetyl-L cysteine, pycnogenols, resveratrol, quercetin and salt. Magnesium, gingko, salt and fludrocortisone, are already used by some physicians.
Studies in the 1970s showed that marijuana, when smoked, lowers intraocular pressure.American Academy of Ophthalmology. Complementary Therapy Assessment: Marijuana in the Treatment of Glaucoma. Retrieved August 2, 2006. 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 that some derivatives of marijuana lowered intraocular pressure when administered orally, intravenously, or by smoking, but not when topically applied to the eye. Many of these studies demonstrated that marijuana — or any of its components — could safely and effectively lower intraocular pressure more than a variety of drugs then on the market. In 2003, the American Academy of Ophthalmology released a position statement asserting that "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 study goes on to say, "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".http://one.aao.org/CE/PracticeGuidelines/Therapy_Content.aspx?cid=9871fa42-cf40-4c1f-b05c-c816d5f93126
The first patient in the United States federal government\'s Compassionate Investigational New Drug program, Robert Randall, was afflicted with glaucoma and had successfully fought charges of marijuana cultivation because it was deemed a medical necessity (U.S. v. Randall) in 1976.http://blogs.salon.com/0002762/stories/2005/02/18/irvRosenbergAndTheCompassi.html
Conventional surgery to treat glaucoma makes a new opening in the meshwork. This new opening helps fluid to leave the eye and lowers intraocular pressure.
Both laser and conventional surgeries are performed to treat glaucoma.
Surgery is the primary therapy for those with congenital glaucoma."Glaucoma, Congenital: GLC3 Buphthalmos." OMIM - Online Mendelian Inheritance in Man. Accessed October 17, 2006.
Generally, these operations are a temporary solution, as there is not yet a cure for glaucoma.
Canaloplasty is an advanced, nonpenetrating procedure designed to enhance and restore the eye’s natural drainage system to provide sustained reduction of IOP. Canaloplasty utilizes breakthrough microcatheter technology in a simple and minimally invasive procedure. To perform a canaloplasty, a doctor will create a tiny incision to gain access to a canal in the eye. 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 will be relieved. [1] [2][3]
Laser trabeculoplasty may be used to treat open angle glaucoma. It is a temporary solution, not a cure. A 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 utilizes a thermal argon laser. The procedure is called argon laser trabeculoplasty or ALT. A newer type of laser trabeculoplasty uses a "cold" (non-thermal) laser to stimulate drainage in the trabecular meshwork. This newer procedure is call selective laser trabeculoplasty or SLT. Studies show that 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.
Laser peripheral iridotomy may be used in patients susceptible to or affected by angle closure glaucoma. During laser iridotomy, laser energy is used to make a small full-thickness opening in the iris. This opening equalizes the pressure between the front and back of the iris, causing the iris to move backward. This uncovers 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 gradual adhesion of the iris to the trabecular meshwork.
The most common conventional surgery performed for glaucoma is the trabeculectomy. Here, a partial thickness flap is made in the scleral wall of the eye, and a window opening made under the flap to remove a portion of the trabecular meshwork. The scleral flap is then sutured loosely back in place. This allows 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. One person can have multiple surgical procedures of the same or different types.
There are also several different glaucoma drainage implants. These 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.
Molteno AC, Polkinghorne PJ, Bowbyes JA. The vicryl tie technique for inserting a draining implant in the treatment of secondary glaucoma. Aust N Z J Ophthalmol. 1986 Nov;14(4):343-54 [4] This is done to reduce postoperative hypotony -- sudden drops in postoperative intraocular pressure (IOP).
Ayyala RS, Zurakowski D et al. Comparison of double-plate Molteno and Ahmed glaucoma valve in patients with advanced uncontrolled glaucoma. Ophthalmic Surg Lasers. 2002 Mar-Apr;33(2):94-101.[5].
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 anti-fibrotic medication like 5-fluorouracil (5-FU) or mitomycin-C (during the procedure), or additional surgery.
Glaucoma has been classified into specific types:Paton D, Craig JA. "Glaucomas. Diagnosis and management." Clin Symp. 1976;28(2):1-47. PMID 1053095.
Primary open-angle glaucoma - This is caused by trabecular blockage which is where the Aqueous humor in the eye drains out. Because the microscopic passage ways are blocked, the pressure builds up in the eye and causes imperceptable 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. The treatment\'s goal is to release the fluid by opening uveoscleral passageways, which are acted upon by prostoglandin agonists. Beta blockers such as timolol, alpha 2 agonist, 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.
Primary closed-angle glaucoma - This is caused by sudden blockage of the flow across the pupil. Pressure will rapidly build up in the eye causing pain and redness. Vision becomes blurred and halos are seen around bright objects. Accompanying symptoms include headache and vomiting. Diagnosis is made from obvious physical findings: pupils dilated, cornea swollen, reduced vision, redness, pain. Treatment is no longer focused on trabecular or uveoscleral passageways. The formation of fluid can be temporarily treated with carbonic anhydrase inhibitors which act on the ciliary process. But the patient will need surgery or laser treatment.
| Pathology of the eye (primarily H00-H59, 360-379) | |
|---|---|
| Eyelid, lacrimal system and orbit | eyelid: inflammation (Stye, Chalazion, Blepharitis) - Entropion - Ectropion - Lagophthalmos - Blepharochalasis - Ptosis - Blepharophimosis - Xanthelasma - Trichiasis
lacrimal system: Dacryoadenitis - Epiphora - Dacryocystitis orbit: Exophthalmos - Enophthalmos |
| Conjunctiva | Conjunctivitis - Pterygium - Pinguecula - Subconjunctival hemorrhage |
| Sclera and cornea | Scleritis - Keratitis - Corneal ulcer - Snow blindness - Thygeson\'s superficial punctate keratopathy - Fuchs\' dystrophy - Keratoconus - Keratoconjunctivitis sicca - Arc eye - Keratoconjunctivitis - Corneal neovascularization - Kayser-Fleischer ring - Arcus senilis - Band keratopathy |
| Iris and ciliary body | Iritis - Uveitis - Iridocyclitis - Hyphema - Persistent pupillary membrane - Iridodialysis - Synechia |
| Lens | Cataract - Aphakia - Ectopia lentis |
| Choroid and retina | Retinitis - Chorioretinitis - Choroideremia - Retinal detachment - Retinoschisis - Retinopathy (Hypertensive retinopathy, Coats disease, Diabetic retinopathy, Retinopathy of prematurity) - Macular degeneration - Retinitis pigmentosa - Retinal haemorrhage - Central serous retinopathy - Macular edema - Epiretinal membrane - Macular pucker |
| Optic nerve and visual pathways | Optic neuritis - Papilledema - Optic atrophy - Leber\'s hereditary optic neuropathy |
| Ocular muscles, binocular movement, accommodation and refraction | Paralytic strabismus: Ophthalmoparesis - Progressive external ophthalmoplegia - Palsy (III, IV, VI) - Kearns-Sayre syndrome
Other strabismus: Esotropia/Exotropia - Hypertropia - Heterophoria (Esophoria, Exophoria) - Brown\'s syndrome - Duane syndrome |
| Visual disturbances and blindness | Amblyopia - Leber\'s congenital amaurosis - Subjective (Asthenopia, Hemeralopia, Photophobia, Scintillating scotoma) - Diplopia - Scotoma - Anopsia (Binasal hemianopsia, Bitemporal hemianopsia, Homonymous hemianopsia, Quadrantanopia) - Color blindness (Achromatopsia) - Nyctalopia (Oguchi disease) - Blindness/Low vision |
| Pupil | Anisocoria - Argyll Robertson pupil - Marcus Gunn pupil/Marcus Gunn phenomenon - Adie syndrome |
| Infectious diseases | Trachoma - Onchocerciasis |
| Other | Nystagmus - Miosis - Mydriasis - Glaucoma - Ocular hypertension - Floater - Leber\'s hereditary optic neuropathy - Red eye - Keratomycosis - Xerophthalmia - Aniridia |
| See also congenital | |
This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia
