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. Sometimes called the silent thief of sight, glaucoma can damage your vision so gradually you may not notice any loss of vision until the disease is at an advanced stage.

Open angle-closure glaucoma, also called wide-angle or primary open angle glaucoma, this is the most common type of glaucoma. The structures of the eye appear normal, but fluid in the eye does not flow properly through the drain of the eye.

The exact cause of primary open-angle glaucoma remains unknown. However, open-angle 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.

• Gradual loss of peripheral vision, usually in both eyes
• Tunnel vision in the advanced stages

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.

Glaucoma treatment often starts with one or more medicated eyedrops. If eyedrops alone don't bring your eye pressure down to the desired level, your doctor may also prescribe an oral medication, usually in the form of a carbonic anhydrase inhibitor. You may need surgery to treat glaucoma if you can't tolerate medications or if they're ineffective. These surgery procedures include laser or filtering surgery, or drainage implants. 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, 38 CFR 4.76, 38 CFR 4.77, 38 CFR 4.78,  and  38 CFR 4.79, diagnostic codes 6061-6091.