Glaucoma is not just one eye disease, but a group of eye conditions resulting in optic nerve damage, which causes loss of vision. Abnormally high pressure inside your eye (intraocular pressure) usually, but not always, causes this damage. Glaucoma is the second leading cause of blindness.

Angle-closure glaucoma, also called closed-angle glaucoma, occurs when the iris bulges forward to narrow or block the drainage angle formed by the cornea and the iris. As a result, iris aqueous fluid can no longer reach the trabecular meshwork at the angle, so the eye pressure increases abruptly. Angle-closure glaucoma usually occurs suddenly (acute angle-closure glaucoma), but it can also occur gradually (chronic angle-closure glaucoma).

For most people, the cause of glaucoma is not known, although both open-angle and closed-angle glaucomas tend to run in families. Many people who develop closed-angle glaucoma have an abnormally narrow drainage angle to begin with. This narrow angle may never cause any problems, so it may go undetected for life.

Angle-closure glaucoma can be a primary or secondary condition. It is called primary when the cause is unknown and secondary when the condition can be traced to a known cause, such as eye injury, inflammation, tumor, advanced cataract or diabetes. In secondary glaucoma, the signs and symptoms can include those of the primary condition as well as typical glaucoma symptoms.

Sudden dilation of the pupils may trigger acute angle-closure glaucoma. Pupils become dilated in response to darkness, dim light, stress, excitement and certain medications. These medications include antihistamines, such as desloratadine (Clarinex) and cetirizine (Zyrtec); tricyclic antidepressants, such as doxepin and protriptyline (Vivactil); and eyedrops used to dilate your pupils for a thorough eye exam.

If eye pressure rises rapidly in closed-angle glaucoma (acute angle-closure glaucoma), people typically notice an abrupt onset of the following symptoms.

• Headache

• Severe eye pain

• Nausea and vomiting (accompanying the severe eye pain)

• Sudden loss of vision

• Blurred vision

• Rainbow-colored halos around lights

• Reddening of the eye

Nausea and vomiting may occur as a response to the increase in eye pressure. Acute angle-closure glaucomais considered a medical emergency, because individuals can lose their vision as quickly as 2 to 3 hours after the appearance of symptoms if the condition is not treated. Individuals who have had open-angle or closed-angle glaucoma in one eye are likely to develop it in the other.

These are some of the tests that can establish a diagnosis of glaucoma:

• Tonometry is a simple, painless procedure that measures your intraocular pressure, after numbing your eyes with drops. It is usually the initial screening test for glaucoma.

• Opthalmoscopic examination check the fibers in your optic nerve, your eye doctor uses instruments to look directly through the pupil to the back of your eye. This can reveal slight changes that may indicate the beginnings of glaucoma.

• Visual field test evaluate your side (peripheral) vision.

• Measuring cornea thickness (pachymetry). Your eyes are numbed for this test, which determines the thickness of each cornea, an important factor in diagnosing glaucoma. If you have thick corneas, your eye-pressure reading may read higher than normal even though you may not have glaucoma. Similarly, people with thin corneas can have normal pressure readings and still have glaucoma.

• Gonioscopy in which a special lens is placed on your eye to inspect the drainage angle.

• Tonography can measure how quickly fluid drains from your eye.

Because severe closed-angle glaucoma is a medical emergency, doctors may use very strong and fast-acting drugs that affect the eye pressure more rapidly than the standard eyedrops or surgery. Doctors may use glycerin or acetazolamide (Diamox) pills or drugs given by vein (such as the mannitol) if they think the eye is vulnerable to high pressure. Eyedrops are also given as soon as possible. Emergency surgery is performed if necessary. Eyedrop medications include:

• Prostaglandin-like compounds. These eyedrops increase the outflow of aqueous humor. Examples include latanoprost (Xalatan) and bimatoprost (Lumigan).

• Beta blockers. These reduce the production of aqueous humor. Examples include timolol (Betimol, Timoptic), betaxolol (Betoptic) and metipranolol (Optipranolol).

• Alpha-agonists. These reduce the production of aqueous humor and increase drainage. Examples include apraclonidine (Iopidine) and brimonidine (Alphagan).

• Carbonic anhydrase inhibitors. These also reduce the production of aqueous humor. Examples include dorzolamide (Trusopt) and brinzolamide (Azopt).

• Miotic or cholinergic agents. These also increase the outflow of aqueous humor. Examples include pilocarpine (Isopto Carpine) and carbachol (Isopto Carbachol).

• Epinephrine compounds. These compounds, such as dipivefrin (Propine), also increase the outflow of aqueous humor.

All patients with glaucoma require treatment and supervision of their intra-ocular pressure, visual fields, and inspection of their optic disks on a regular basis.

• Consider service connection on a presumptive basis as a chronic condition (38 CFR 3.307). This condition is to be considered as an organic disease of the nervous system.

• Consider entitlement to Auto and auto adaptive equipment under 38 CFR 3.308 if there is permanent impairment of vision in both eyes consisting of central visual acuity of 20/200 or less in the better eye, with corrective glasses, or central visual acuity of more than 20/200 if there is a field defect in which the peripheral field has contracted to such an extent that the widest diameter of visual field subtends an angular distance no greater than 20° in the better eye.

• Consider entitlement to specially adapted housing under 38 U.S.C. 2101(a)(2)(A)(i) if there is visual impairment to the degree specified in 38 CFR 3.809(b)(2).

• Review for potential entitlement to special monthly compensation under 38 CFR 3.350 when there is loss/loss of use of one or both eyes, light perception only; visual acuity 5/200 or less; the vision field is reduced to 5 degree concentric contraction in both eyes; or blindness with no light perception in one or both eye.

• Evaluate on the basis of either visual impairment due to the particular condition or on incapacitating episodes, whichever results in a higher evaluation.

• For the purposes of evaluation under 38 CFR 4.79, an incapacitating episode is an eye condition severe enough to require a clinic visit to a provider specifically for treatment purposes.

• Examples of treatment may include but are not limited to: Systemic immunosuppressants or biologic agents; intravitreal or periocular injections; laser treatments; or other surgical interventions.

• For the purposes of evaluating visual impairment due to the particular condition, refer to 38 CFR 4.75-4.78 and to 38 CFR 4.79, diagnostic codes 6061-6091.