5th year medical student
UTG Medical Students’ Association
Glaucoma is a slowly developing disease of the eyes that can lead to irreversible blindness. In fact, it is the leading cause of irreversible blindness globally. Research has shown that glaucoma is highly prevalent in our sub-region, West Africa. In some areas, it is as high as 19%, meaning one (1) in every five (5) people will have glaucoma. It used to be the third leading cause of blindness in The Gambia after cataracts and Trachoma in 1989 and 1996 surveys. In 2019, 71% of blindness was due to cataracts, a reversal of the modest decline in the proportion from 55% to 45% between 1986 and 1996 but in line with the recent Global Burden of Disease. Huge progress has been made to achieve the elimination of trachoma as a public health problem in 2021. In the developed world, more than 50% of the people are unaware that they have glaucoma but in Africa, more than 90% are unaware that they have glaucoma.
Blindness? What is this devastating disease all about?
Glaucoma is a group of eye diseases that can cause vision loss and blindness by damaging a nerve in the back of your eye called the optic nerve. In normal vision, light rays enter the eyes through the cornea. This is a clear dome-shaped surface that covers the front of the eye. From the cornea, the light passes through the pupil. The iris, or the colored part of the eye controls the amount of light passing through. From there, it then hit the lens and passes through a clear, jelly-like substance that fills the centre of the eye called the vitreous humour. This fluid gives the eye its round shape and is responsible for the pressure inside the eye. Finally, the light reaches the retina where the image is inverted. The optic nerve is then responsible for carrying the signals from the retina to the visual cortex of the brain, where the signals are turned into images.
Are you wondering what could happen if the connection between the eye and the brain is disrupted? Exactly, it will lead to vision loss. Glaucoma leads to blindness by causing gradual programmed death (apoptosis) of the nerve cells of the optic nerve. However, the disease progression of glaucoma is a bit different from other causes of blindness. This is due to slow and progressive loss of vision outside the central gaze of focus.
What Causes Glaucoma?
The exact cause of Glaucoma is still a medical mystery as it is still not known. However, most glaucoma is associated with elevated eye pressure. Elevated eye pressure happens as the result of a buildup of fluid that flows throughout the inside of the eye. This fluid also is known as aqueous humour. It usually drains through a tissue located at the angle where the iris and cornea meet. This tissue also is called the trabecular meshwork. The cornea is important to vision because it lets light into the eye. When the eye makes too much fluid or the drainage system doesn’t work properly, eye pressure may increase. The increased eye pressure may eventually lead to bulging that causes progressive death of the optic nerve.
Type of glaucoma
Open-angle glaucoma
This is the most common form of glaucoma. The drainage angle formed by the iris and cornea remains open. But other parts of the drainage system don’t drain properly. This may lead to a slow, gradual increase in eye pressure.
Angle-closure glaucoma
This form of glaucoma occurs when the iris bulges. The bulging iris partially or completely blocks the drainage angle. As a result, fluid can’t circulate through the eye and pressure increases. Angle-closure glaucoma may occur suddenly or gradually.
Normal-tension glaucoma
No one knows the exact reason why the optic nerve becomes damaged when eye pressure is normal. The optic nerve may be sensitive or experience less blood flow. This limited blood flow may be caused by the buildup of fatty deposits in the arteries or other conditions that damage circulation. The buildup of fatty deposits in the arteries also is known as atherosclerosis.
Glaucoma in children
A child may be born with glaucoma or develop it in the first few years of life. Blocked drainage, injury or an underlying medical condition may cause optic nerve damage.
Pigmentary glaucoma
In pigmentary glaucoma, small pigment granules flake off from the iris and block or slow fluid drainage from the eye. Activities such as jogging sometimes stir up the pigment granules. That leads to a deposit of pigment granules on tissue located at the angle where the iris and cornea meet. The granule deposits cause an increase in pressure. Glaucoma tends to run in families. In some people, scientists have identified genes related to high eye pressure and optic nerve damage.
Risk factors
Glaucoma can damage vision before you notice any symptoms. So be aware of these risk factors:
o High internal eye pressure, also known as intraocular pressure
o Age over 55
o Black, Asian or Hispanic heritage
o Family history of glaucoma
o Certain medical conditions, such as diabetes, migraines, high blood pressure and sickle cell anaemia
o Corneas that are thin in the centre
o Extreme nearsightedness or farsightedness
o Eye injury or certain types of eye surgery
o Taking corticosteroid medicines, especially eye drops, for a long time
Some people have narrow drainage angles, putting them at increased risk of angle-closure glaucoma.
What are the signs and symptoms of glaucoma?
Initially, there are no symptoms for glaucoma, the person is unaware and would not complain of anything. The person would be seen like everyone else unless he/she is checked for the risk factors by an eye specialist, they would think they have no problem.
So when the disease is early, there are no symptoms. When the disease is advanced, then the vision is poor. The person may start bumping into objects because he/she loses peripheral vision. When it is beginning to get dark, vision tends to get worse. So, bumping into objects could be the earliest sign of the disease.
When loss of peripheral vision sets in, the person can only see through a narrow area, this is called tunnel vision.
Is there any cure for glaucoma?
Sadly, when one has glaucoma and it is diagnosed early, it can be managed but it cannot be cured. The damage caused by glaucoma cannot be reversed. But treatment and regular checkups can help slow or prevent vision loss, especially if you catch the disease in its early stages. Glaucoma is treated by lowering intraocular pressure. Treatment options include prescription eye drops, oral medicines, laser treatment, surgery or a combination of approaches.
How can you prevent blindness due to glaucoma?
These steps may help detect and manage glaucoma in its early stages. That may help to prevent vision loss or slow its progress.
Get regular eye examinations. Regular comprehensive eye exams can help detect glaucoma in its early stages before significant damage occurs. As a general rule, the American Academy of Ophthalmology recommends a comprehensive eye exam every 5 to 10 years if you’re under 40 years old; every 2 to 4 years if you’re 40 to 54 years old; every 1 to 3 years if you’re 55 to 64 years old; and every 1 to 2 years if you’re older than 65.
If you’re at risk of glaucoma, you’ll need more frequent screening. Ask your healthcare provider to recommend the right screening schedule for you.
Know your family’s eye health history. Glaucoma tends to run in families. If you’re at increased risk, you may need more frequent screening.
Wear eye protection. Serious eye injuries can lead to glaucoma. Wear eye protection when using power tools or playing sports.
Take prescribed eye drops regularly. Glaucoma eye drops can significantly reduce the risk that high eye pressure will progress to glaucoma. Use eye drops as prescribed by your health care provider even if you have no symptoms.
Conclusion
Glaucoma is also known as “the silent thief of sight” because most initial stages of the disease do not manifest any sign or symptom. It is the leading cause of irreversible blindness globally and has the highest prevalence in the African sub-region. There is no known cause of glaucoma however it is associated with increased eye pressure which could be a result of many factors. Advanced age and family history are common risk factors; however, people at a young age can also get the disease.
Glaucoma has no cure but it can be managed to delay blindness. In addition, it is highly recommended to get your eyes screened because early diagnosis can be helpful in the management of the disease. It is wise to do a medical checkup not only when you are sick, to detect diseases early and prevent possible complications. Finally, it is important to note that, not every person that wears glasses or has visual impairment has glaucoma.
