What Is Narrow-Angle Glaucoma?

Glaucoma is a medical term that refers to a broader range of underlying conditions. Glaucoma is the state where there is vision impairment due to damage to the optic nerve. The optic nerve is part of the central nervous system and supplies visual impulses from the eye’s retina to the optic centres in the brain.

Glaucoma is extremely prevalent worldwide and is the leading cause of blindness according to the World Health Organisation.

The danger of glaucoma is that it is a progressive condition and that damage to the optic nerve cannot be reversed. Management of glaucoma thus focuses on prevention of disease progression.

There are different types of glaucoma. The two main types are open (wide) angle glaucoma and narrow (closed) angle glaucoma.

The “angel” referred to in glaucoma is the angle between the cornea and iris. The aqueous fluid of the eye drains through this angle. In wide angle glaucoma, the angle is open, in contrast to closed angle glaucoma where the angle is blocked, and fluid cannot drain as needed.

Narrow-angle glaucoma is less common than wide angle glaucoma and usually presents in about ten percent of glaucoma cases. Narrow-angle glaucoma may be either acute or chronic. In contrast to wide angle glaucoma, acute narrow-angle glaucoma will present with typical symptoms suggestive of the disease. Chronic narrow-angle glaucoma is most often asymptomatic.

Diagnosis of acute narrow-angle glaucoma is made by clinical examination and measurement of the affected eye’s intraocular pressure. Chronic narrow-angle glaucoma is diagnosed by gonioscopy with definitive changes to the optic nerve. Gonioscopy, may not be possible in acute closed angle glaucoma due to clouding of the cornea and severe pain and discomfort in the eye.

Risk factors for any form of glaucoma include old age (above sixty years), family history of glaucoma, African descent and myopia (near-sightedness).

What Are The Symptoms Of Narrow-Angle Glaucoma?

Acute narrow-angle glaucoma is an ophthalmic emergency. If not treated promptly it can lead to irreversible blindness.

Symptoms suggestive of acute narrow-angle glaucoma include:

• Red and painful eye
• Sudden onset loss of vision
• Headache
• Nausea and vomiting
• Dilated pupil
• Chronic narrow-angle glaucoma presents similarly to wide angle glaucoma. It is usually asymptomatic with progressive loss of vision. Slow peripheral visual field loss is common.

What Are The Causes Of Narrow-Angle Glaucoma?

Under normal circumstances, the ciliary bodies surrounding the iris produce a liquid called aqueous humour. This liquid is needed to maintain normal pressures in the eye and gives the eyeball its spherical shape.

Narrow-angle glaucoma occurs when there is a blockage of aqueous humour drainage from the eye, due to a closure of the angle between the lens and the iris.

Aqueous humour is continually being produced, and there is a delicate balance between production and drainage. The fluid drains via a trabecular meshwork, through the angle between the iris and cornea. Due to certain conditions, this angle can be closed or "narrowed", preventing drainage of fluid. The result is increased intra-ocular pressure (IOP) leading to damage of the optic nerve.

Narrow-angle glaucoma is caused by any condition that either pushes or pulls the iris forward and thereby closing the normal angle needed for drainage. Causes and predisposing factors for narrow-angle glaucoma include:

Iris abnormalities: Pupillary blockage may occur. This causes fluid to become trapped behind the iris and pushes the lens forward. Consequently, the drainage angle closes and leads to increased pressure in the anterior chamber of the eye.

Iris plateau: In this condition, the iris is too close to the lens, and causes blockage of the trabecular meshwork when the pupil dilates.

The risk for narrow-angle glaucoma is higher in Asian populations and lower in African and Caucasian groups. Female Caucasians are three times more likely to be affected than Caucasian males.

Chronic narrow-angle glaucoma typically occurs in old age. As one age, the lens continues to grow. In some cases, the growth can push the iris forward and close the angle needed to drain.

Secondary causes of narrow-angle glaucoma occur when other conditions obstruct flow such as uveitis, retinal proliferation, or post-inflammatory scarring.

What Are The Things One Should Do To Manage Narrow-Angle Glaucoma?

• Seek emergency medical help if suspected symptoms of acute narrow-angle glaucoma arise. Treatment needs to be prompt to prevent irreversible blindness.
• Educate yourself about glaucoma, and which medications can potentially aggravate the condition.
• Avoid areas with dim lighting. Pupil dilatation can precipitate an acute attack.
•  Cardiovascular exercise has shown to decrease IOP. This appears to be more useful in wide angle as opposed to closed angle glaucoma. Exercise is however beneficial to general health and is always a recommendation.
• Lose weight. Some studies suggest that a lower BMI may have a lowering effect on IOP.

What Are The Things One Should Avoid To Manage Narrow-Angle Glaucoma?

• Fluid intake can transiently increase IOP. It is advisable to drink smaller amounts of fluid more regularly.
• Decongestants and antihistamines should be avoided, as they can lead to an acute closed angle episode.
• Do not smoke. Smoking has been shown to moderately increase IOP and predisposes to atherosclerotic disease of the retinal vessels, which will worsen vision loss.

What Are The Best Foods For Narrow-Angle Glaucoma?

• Anti-oxidants have a beneficial effect on vision, and specifically any glaucoma. These include foods rich in:

  Vitamin C: Oranges, berries, tomatoes, peppers

  Vitamin E: Butter, milk, nuts, avocados

  Vitamin A: Sweet potato, egg yolks, papaya, grapefruit

  Lutein and zeaxanthin are carotenoids that are very powerful in assisting with vision due to their strong antioxidant effect. They can be found in green leafy vegetables such as spinach, kale, broccoli, lettuce, pumpkin and egg yolks.

  Zinc-rich foods: Seafood, beans, grain cereals, eggs, meat

• Bilberry (an extract from blueberries) can assist in reducing vision loss by improving the condition of optic blood vessels. Other dark berries such as cranberries or mulberries may also be useful.

What Are The Worst Foods For Narrow-Angle Glaucoma?

Caffeine containing foods. Caffeine increases the intraocular pressure on the in the eye transiently and it is advisable to avoid. 

What Are The Medicines For Narrow-Angle Glaucoma?

What Are The Tips To Manage Narrow-Angle Glaucoma?

Gingko Biloba may assist by increasing blood flow to the retina. Ongoing studies are assessing the use of melatonin supplements in lowering intra-ocular pressure.