Written by Honor Whiteman, Published on Medical News Today. January 13, 2016.

Glaucoma is a primary cause of vision loss and blindness in the US, affecting around 2.7 million people - a number that is expected to reach 4.2 million by 2030. While severe glaucoma-related vision loss can often be prevented, there is one major barrier: around half of patients with the disease do not know they have it.


Glaucoma is a group of conditions that cause damage to the eye's optic nerve - a cluster of more than a million nerve fibers.

The optic nerve links the retina - the light-sensitive layer at the back of the eye - to the brain; any damage to the optic nerve can lead to vision loss and blindness.

Glaucoma is often referred to as the "sneak thief of sight" - because it rarely presents symptoms; it can take away as much as 40% of a person's vision without them noticing, and once this vision has gone, it cannot be restored.

Early diagnosis, however, opens the door to a number of treatment options that can halt glaucoma-related vision loss.

In line with Glaucoma Awareness Month this January, we look at the risk factors for glaucoma and how an early diagnosis can be achieved, increasing the likelihood of stopping the sight-stealing disease in its tracks.


Types of glaucoma

Glaucoma can occur in one or both eyes, and there are two main types - open-angle glaucoma - the most common form, accounting for around 90% of all cases - and angle-closure glaucoma.

Open-angle glaucoma also called primary or chronic glaucoma, is characterized by a wide, open angle between the iris and the cornea.

Fast facts about glaucoma

  •     Glaucoma is the second leading cause of blindness worldwide
  •     There is no cure for glaucoma; early detection is key in preventing vision loss from the disease
  •     Unfortunately, around 10% of people who receive suitable treatment for glaucoma still experience vision loss.

It develops when a clear fluid called the aqueous humor leaves the eye's anterior chamber too slowly through the drainage canals, resulting in a fluid build-up. This build-up increases eye pressure, causing damage to the optic nerve that can lead to vision loss.

Vision loss from open-angle glaucoma normally begins with peripheral vision - vision outside the central area of focus - before affecting central vision.

In its early stages, open-angle glaucoma presents no symptoms and vision appears normal, explaining why around half of individuals with glaucoma are unaware they are affected.

In angle-closure glaucoma, also called acute or narrow-angle glaucoma, the angle between the iris and the cornea is narrow or closed. The drainage canals in the eye become fully blocked, leading to a sudden rise in eye pressure that can damage the optic nerve.

Unlike open-angle glaucoma, angle-closure glaucoma does present symptoms, including eye redness, blurred vision, severe pain and nausea.

Other less common forms of glaucoma include normal-tension glaucoma, in which optic nerve damage occurs despite normal eye pressure, and congenital glaucoma - a rare condition in babies, in which the eye's drainage canals fail to develop or develop abnormally.


The risks and warning signs

Glaucoma is most common among adults over the age of 60, individuals with a family history of the disease, and black people.

According to the Glaucoma Research Foundation, black Americans are around six to eight times more likely to develop glaucoma than white Americans, and black Americans are around 14-17 times more likely to go blind from the disease than white Americans of the same age group.

Other risk factors for glaucoma include diabetes, severe nearsightedness, previous eye injuries, steroid use and a history of severe anemia.

While most glaucoma cases do not present symptoms in the early stages, there are some warning signs to look out for. These include:

  •     Red-rimmed, swollen or crusty eyelids
  •     Watery eyes
  •     Dry eyes with itching or burning
  •     Double vision
  •     Recurrent pain in or around the eyes
  •     Squinting or blinking due to unusual light sensitivity
  •     Dark spots at central vision
  •     Change in iris color.

More severe signs include sudden blurred vision, sudden loss of vision in one eye, halos or rainbows around light, and black spots or flashes of light.

While these symptoms may not necessarily be related to glaucoma, the presence of at least one warrants a visit to an eye doctor - an optometrist or ophthalmologist - for an eye examination as soon as possible.


Regular eye exams 'key to protecting vision'

However, to identify glaucoma - and any other eye problems - as early as possible, you should have regular eye examinations before symptoms appear; this is key to preventing vision loss.

"Early detection by having a comprehensive dilated eye exam every 1-2 years is key to protecting vision, especially if you are at higher risk," says Dr. Paul Sieving.

A comprehensive dilated eye exam is considered the best way to detect glaucoma. It includes a visual acuity test, (to measure ability to see at various distances), a visual field test (to assess peripheral vision), a dilated eye exam (to assess damage to the retina and optic nerve), tonometry (to measure eye pressure) and pachymetry (to measure thickness of the cornea).

According to the National Eye Institute (NEI) - part of the National Institutes of Health (NIH) - black Americans are advised to start having annual comprehensive dilated eye exams at the age of 40 because of their higher risk of glaucoma, while all other Americans are recommended to have the exams annually from the age of 60.

However, a survey from the Glaucoma Research Foundation reveals that around less than half of Americans have an annual comprehensive eye exam, meaning millions of us are putting our vision at risk.

Around 120,000 people in the US are blind as a result of glaucoma, accounting for 9-12% of all blindness cases in the country. The sad truth is, many of these cases could have been prevented with early diagnosis.

Dr. Paul Sieving, director of the NEI, says:

    "If glaucoma is detected in its early stages, pressure can be controlled through medication or surgery, and the progression of the disease can be delayed.

    Early detection by having a comprehensive dilated eye exam every 1-2 years is key to protecting vision, especially if you are at higher risk."

Treatments for glaucoma

The most common treatments for early glaucoma are medications in the form of eye drops or pills, including prostaglandins, beta-blockers and alpha-adrenergic agonists. These work by reducing fluid production in the eye or reducing eye pressure by encouraging fluid drainage.

The NEI note that because most individuals with early stage glaucoma experience no symptoms, they often forget to take or stop using their medication. However, they stress that treatment success is highly dependent on regular use.

Laser trabeculoplasty is another treatment for glaucoma, in which a high-intensity light beam is used to make holes in the eye's drainage canals, allowing the fluid to drain more effectively and reducing eye pressure.

While studies have shown that laser trabeculoplasty is effective for reducing eye pressure in most patients with glaucoma, the effects may diminish for some people, and a second treatment may be required.

Glaucoma patients may also undergo a form of surgery called trabeculectomy, in which a small area of tissue is removed from the eye wall in order to make a new hole for fluid drainage.

According to the NEI, trabeculectomy is around 60-80% effective for reducing eye pressure in glaucoma patients.

While such treatments do not provide a 100% success guarantee, if used early enough, they can be highly effective for delaying glaucoma progression and preventing vision loss.


Poor glaucoma awareness discouraging regular eye exams

So, if glaucoma-related blindness is highly preventable with early diagnosis and treatment, why do so many of us avoid regular eye exams to find out if we have the disease? It seems largely down to lack of awareness.

The results of a Prevent Blindness America survey found that 30% of survey participants had never heard of glaucoma, while around half had heard of the condition but were unsure of what it is.

Furthermore, while around 20% of participants surveyed knew that glaucoma was associated with increased eye pressure, most thought the condition would present symptoms, that it could be easily cured and that it did not cause blindness.

Health professionals across the globe are in agreement that educating the public about glaucoma is key to encouraging more people - particularly high-risk individuals - to undergo regular eye exams.

This is the key message of Glaucoma Awareness Month - a campaign that aims to increase public knowledge about the disease.

As well as providing educational resources about glaucoma to the general public, the campaign hopes to encourage health professionals to better inform patients about glaucoma and the devastating impact it can have on vision.

While glaucoma is a leading cause of blindness, it does not have to be. The take-home message of this article is to have your eyes checked regularly - it could save your sight.

 

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