Glaucoma can take away as much as 40% of a person's sight without them realizing.
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.
- 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.
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 can be a warning sign for glaucoma, though the disease often presents no symptoms in the early stages.
- 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.
On the next page, we look at the importance of regular eye screening, the treatment options for glaucoma, and we investigate what is discouraging people from routine eye exams.