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Definition

What is primary open-angle glaucoma?

Glaucoma refers to a group of eye conditions that lead to damage to the optic nerve head with progressive loss of cells that provides eyesight. This leads to a progressive loss of visual field. There are typical optic nerve changes on slit-lamp examination. Glaucoma is usually associated with an intraocular pressure (IOP – pressure of fluid in the eye) above the normal range.

How common is primary open-angle glaucoma?

Primary open-angle glaucoma can affect patients at any age. It can be managed by reducing your risk factors. Please discuss with your doctor for further information.

Symptoms

What are the symptoms of primary open-angle glaucoma?

Simple (primary) open-angle glaucoma (POAG) is a progressive, chronic condition characterized by:

  • IOP at some point greater than 21 mm Hg (normal range: about 10-21 mm Hg).
  • An open iridocorneal angle (between the iris and the cornea, where the aqueous flows out).
  • Glaucomatous optic neuropathy.
  • Visual field loss compatible with nerve fiber damage.
  • An absence of an underlying cause.
  • It is usually bilateral.

Unfortunately, in the vast majority of cases, patients are asymptomatic. Because initial visual loss is to peripheral vision and the field of vision is covered by the other eye, patients do not notice visual loss until severe and permanent damage has occurred, often impacting on central vision. By then, up to 90% of the optic nerve fibres may have been irreversibly damaged.

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my doctor?

If you have any signs or symptoms listed above or have any questions, please consult with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.

Causes

What causes primary open-angle glaucoma?

It is believed that something is wrong with the ability of the cells in the trabecular meshwork – an area of tissue in the eye located around the base of the cornea, near the ciliary body, and is responsible for draining the fluids from the eye – to carry out their normal function, or there may be fewer cells present, as a natural result of getting older.

Because the trabecular meshwork does not let fluid drain properly, it increases IOP. These theories, as well as others, are currently being studied and tested at numerous research centers across the country.

Risk factors

What increases my risk for primary open-angle glaucoma?

There are many risk factors for primary open-angle glaucoma, such as:

  • Age – commonly appear in people over the age of 65 (and rarely before the age of 40).
  • Family history – there is a clear inherited component in many individuals.
  • Race – it is three to four times more common in Afro-Caribbean people.
  • Ocular hypertension – this is a major risk factor for the development of glaucoma with about 9% of patients developing glaucoma over five years if left untreated.
  • Other factors – myopia (short-sightedness), retinal disease (e.g., central retinal vein occlusion, retinal detachment and retinitis pigmentosa), diabetes, systemic hypertension and possibly also systolic hypotension may also contribute to risk.

Diagnosis & Treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

 

How is primary open-angle glaucoma diagnosed?

An ophthalmologist will examine the eye thoroughly for evidence of glaucoma, comorbidity or an alternative diagnosis to the apparent findings. The details of a glaucoma assessment can be summarized as:

  • Gonioscopy – a technique used to measure the angle between the cornea and the iris to assess whether the glaucoma is open-angle or closed-angle.
  • Corneal thickness – this influences the IOP reading. If it is thicker than usual, it will take greater force to indent the cornea and an erroneously high reading will be obtained.
  • Tonometry – this is the objective measurement of IOP, usually based on the assessment of resistance of the cornea to indent. The normal range is considered to be 10 mm Hg-21 mm Hg.
  • Optic disc examination – this is a direct marker of disease progression. Optic disc damage is assessed by looking at the cup:disc ratio: normal is 0.3, although it can be up to 0.7 in some normal people:
  • Visual fields – assessment requires the co-operation of the patient and can also be affected by fatigue, spectacle frames, miosis and media opacities. See also the separate Visual Field Defects article.

How is primary open-angle glaucoma treated?

Current medical therapy for primary open-angle glaucoma is limited toward lowering intraocular pressure. A rational approach to choosing antiglaucoma medications should minimize the number of medications and the probability of significant adverse effects.

If one medication is not adequate in reaching the target pressure, a second medication should be chosen that has a different mechanism of action, so that the 2 drug therapies will have an additive effect.

Medications

Medications used in the management of primary open-angle glaucoma include the following:

  • Beta-adrenergic blockers (e.g., levobunolol, timolol, carteolol, betaxolol, metipranolol, levobetaxolol)
  • Adrenergic agonists (e.g., brimonidine, apraclonidine)
  • Less-selective sympathomimetics (e.g., dipivefrin, epinephrine)
  • Carbonic anhydrase inhibitors (e.g., dorzolamide, brinzolamide, acetazolamide, methazolamide)
  • Prostaglandin analogs (e.g., latanoprost, bimatoprost, travoprost, unoprostone, tafluprost)
  • Miotic agents (e.g., pilocarpine)
  • Hyperosmotic agents (e.g., isosorbide dinitrate, mannitol, glycerin)
  • Beta-blocker/alpha agonist combination (e.g., brimonidine/timolol)
  • Beta-blocker/carbonic anhydrase inhibitor combination (e.g., dorzolamide/timolol)
  • Alpha agonist/carbonic anhydrase inhibitor (e.g., brimonidine/brinzolamide)

Laser therapy

Laser can be used as primary or adjunctive treatment. It is indicated in cases of noncompliance with medications or if the patient is on maximum tolerated medical therapy and needs further intraocular pressure reduction. The following are laser options that may be used for primary open-angle glaucoma:

  • Argon laser trabeculoplasty (ALT)
  • Selective laser trabeculoplasty (SLT)
  • Micropulse diode laser trabeculoplasty (MDLT)

Surgery

Surgery is indicated in primary open-angle glaucoma when glaucomatous optic neuropathy worsens (or is expected to worsen) at any given level of intraocular pressure and the patient is on maximum tolerated medical therapy.

The following are surgical options that may be used for primary open-angle glaucoma:

  • Trabeculectomy
  • Drainage implant surgery
  • Cyclophotocoagulation (CPC)

Minimally invasive glaucoma surgery (MIGS) consists of newer techniques that hold potential as surgical options in primary open-angle glaucoma, including the following:

  • Deep sclerectomy/viscocanalostomy
  • 360-degree suture canaloplasty
  • Trabectome ®
  • Endoscopic cyclophotocoagulation (ECP)
  • CyPass Microstent ®
  • iStent implant ®
  • Gonioscopy-assisted transluminal trabeculotomy (GAAT)
  • Kahook dual blade ®

Lifestyle changes & Home remedies

What are some lifestyle changes or home remedies that can help me manage primary open-angle glaucoma?

The following lifestyles and home remedies might help you cope with primary open-angle glaucoma:

  • Eat a healthy diet
  • Exercise safely
  • Limit your caffeine
  • Sip fluids frequently
  • Sleep with your head elevated
  • Take prescribed medicine

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Sources

Review Date: April 14, 2017 | Last Modified: April 14, 2017

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