Glaucoma: The Silent Vision Thief

Dr Neetha K I R is an associate professor, glaucoma specialist, department of opthalmology, Kasturba Medical College and Hospital, MAHE, Manipal.

March 16, 2023

What is Glaucoma?
Glaucoma is a disorder involving gradual and irreversible damage of the optic nerve. It is usually associated with a high pressure inside the eye (intraocular pressure).

What happens if the optic nerve is damaged?
If the optic nerve is damaged due to glaucoma, it can result in the loss of peripheral vision (edge or side vision) in early stages and blindness if left untreated.

Are there any symptoms of glaucoma?
Glaucoma is known as the “silent thief of vision” and is typically associated with painless and progressive loss of vision that may not produce any symptoms. More than 50% of the individuals with glaucoma are unaware that they have the disease.

Why should we know about glaucoma?
Glaucoma is the leading cause of irreversible blindness in the world. The vision lost due to glaucoma cannot be regained. It is important that we are all aware of glaucoma so that we can alert members of our community about the need for regular eye checks, which allow earlier detection of glaucoma and, hence, saved sight.

What is normal intraocular pressure?
The normal intraocular pressure ranges from 10 to 21 mmHg.

How does the pressure inside the eye build up?
There is continuous production of a nourishing fluid inside the eye called ‘aqueous humor’, this fluid drains through a space between the cornea and iris called the ‘angle’. If there is any obstruction to the outflow of aqueous, the pressure inside the eye increases.

Are there different types of glaucoma?
There are two main types of glaucomas- open angle glaucoma and angle closure glaucoma. The aqueous humor fluid inside the eye drains through the angle between the iris and cornea.

In open angle type of glaucoma, even though the angle is open, there is an increased resistance to outflow of aqueous fluid, leading to rise in intraocular pressure and damage of the optic nerve.

In angle closure glaucoma, access to the angle is closed and fluid cannot drain from the eye. This leads to build up of pressure.

What increases the risk of developing glaucoma?

• Family history – this means that if your parents or siblings develop glaucoma there is nearly 10 times higher risk of you developing glaucoma.

• Age – the risk of developing glaucoma can increase as you get older. Ideally everyone over the age of 40 should get their eyes screened for glaucoma.

• Ethnic group – Asian people are at a higher risk of developing angle closure glaucoma and people of African descent are more susceptible to develop open angle glaucoma.

• Short sightedness (myopia) and farsightedness (hypermetropia) –Myopia increases the risk of open angle glaucoma and hypermetropia increases the risk of angle closure glaucoma.

• Diabetes – can be associated with glaucoma.

• Glaucoma can develop as a complication of other eye diseases.

Glaucoma Detection:

Why is early detection important in glaucoma?
Glaucoma is an asymptomatic disease. This is because glaucoma tends to damage the outer edge of the visual field and works slowly inwards. The patient may not notice a problem until the disease becomes severe and affects the central part of the eye and vision. With early detection, early treatment is possible and irreversible blindness can be prevented.

How can one get screened for glaucoma?
Glaucoma screening is possible with intraocular pressure measurement and careful examination of the optic nerve inside the eye using special lenses/equipment. If found suspicious, it is important to undergo more detailed testing.

What are the tests available to detect glaucoma?
• Visual field test: This test is important to check the functioning of the optic nerve. In glaucoma, the edge or sides of the vision are affected first, and this test helps detect it.
• OCT (Optical coherence tomography): This is a scan that measures the thickness of the optic nerve and can thus detect damage.

Are there any other tests done for glaucoma?
• Gonioscopy is a test done routinely for glaucoma. This is done to examine the angle to see if it is open or closed.
• Pachymetry is another test that is done to measure the thickness of the cornea. Corneal thickness affects the eye pressure and can affect the treatment.
• Optic nerve/disc photography: this is done to document the damage at the optic nerve and for comparison in future.

Is it necessary to repeat the glaucoma tests?
Yes, it is important to do so. Glaucoma is a disease for lifetime. Tests have to be repeated at regular intervals to determine whether the disease is under control or not. (This is comparable to diabetes where blood sugars are repeated at regular intervals). The tests that have to be repeated are visual fields and OCT.

Glaucoma treatment

Can glaucoma be cured?
Glaucoma cannot be cured. It can be treated to prevent further damage to the optic nerve. Any damage that has already occurred cannot be reversed.

What are the treatment options available for glaucoma?
Treatment for glaucoma can be in the form of eye drop medicines, lasers, or surgery.

For how long is the glaucoma treatment?
Glaucoma treatment is a lifelong process. Even after initiating treatment, it is important to go for regular follow up visits to the doctor.

Can glaucoma treatment restore the lost vision?
No, glaucoma treatment cannot restore lost vision. It can only prevent further damage. This is why early detection and appropriate treatment is very important.

How many times should glaucoma drops be used, on a daily basis?
Some glaucoma medicines are used once daily, some twice daily and some thrice daily. Depending on how severe your glaucoma is, you may be on multiple medications. Speak to your doctor to determine the correct dosing of your medications.

I have an appointment with the doctor tomorrow, should I use the drops before going for check up?
It is important that you use the medicines even on the day you go for your eye test. This will help the doctor determine if the medicine is acting adequately in bringing down the pressure.

Is glaucoma surgery similar to cataract surgery?
No, glaucoma surgery is different. In conventional glaucoma surgery (trabeculectomy) we are trying to bring down the eye pressure by diverting the aqueous fluid from the eye.

The follow up period after surgery is longer and more frequent in glaucoma surgery. Post-operative medications are also given for a longer duration after glaucoma surgery compared to cataract surgery.

Are there any glaucoma surgeries where the follow up period is shorter?
There are newer glaucoma surgeries called ‘Minimally Invasive Glaucoma Surgeries (MIGS)’ where the post operative recovery phase is quicker. These surgeries have lesser complication risks compared to conventional trabeculectomy, but they may not be as effective.

I underwent glaucoma surgery 6 months ago. Does that mean I am free of glaucoma?
No. Even after successful glaucoma surgery it is essential to monitor the disease with the doctor as glaucoma can worsen without you being aware of it.

I underwent trabeculectomy 3 years ago, but the pressure is now increasing. Why is this happening?
In some cases, trabeculectomies fail over time and eye pressure increases. This is due to normal healing and scarring process in the eye. In such cases you may be started on additional glaucoma eye drops or you may be advised to undergo a second surgery.

What are glaucoma tube surgeries?
Tube surgery or ‘Glaucoma Drainage Device’ surgery is done to divert aqueous fluid by implanting a tube inside the eye. This is recommended in failed trabeculectomies and glaucomas that develop secondary to other problems in the eye.

Special information for angle closure glaucoma

How is angle closure glaucoma different from open angle glaucoma?
Majority of angle closure glaucoma patients are similar to open angle glaucoma patients, as they may not have any symptoms of the disease.

But a small group of angle closure patient may present with dramatic symptoms such as nausea, vomiting, severe eye pain, headache, blurred vision and rainbow-colored haloes around lights. This is due to sudden build up of pressure in the eye when the iris blocks the angle of the eye.

How is treatment of angle closure glaucoma different?
Angle closure glaucoma patients need to undergo an additional LASER procedure called ‘iridotomy’. This laser procedure opens the angle in most of the patients. Once the angle is open, they are treated similar to open angle glaucoma patients.

Are there any special precautions that angle closure patients have to take?
Yes, angle closure patients who have not undergone laser iridotomy have to avoid doing near work in dim lighting conditions, they have to avoid cold medications like nasal sprays or antihistamine tablets. They also have to visit an eye doctor immediately if they notice rainbow-colored rings around lights like head lamps of cars, or if they develop redness/eye pain/ headache.

Who are at higher risk of angle closure glaucoma?
• Older or middle aged people
• Women
• People with farsightedness (hyperopia)
• Asian origin people

It is important for you to get yourself regularly screened for glaucoma. If you have been diagnosed to have glaucoma, effective treatment options are now available. Regular treatment and follow up can help you to preserve your vision for your lifetime.

You can live happily with glaucoma and enjoy an excellent quality of life, particularly if the disease is detected early and treated in time. Always remember that once you have glaucoma, you will have to be under the care of an eye doctor for the rest of your life.

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By Dr Neetha K I R
Dr Neetha K I R is an associate professor, glaucoma specialist, department of opthalmology, Kasturba Medical College and Hospital, MAHE, Manipal.
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Comment on this article

  • Rita, Germany

    Thu, Mar 16 2023

    Thank you Prof.Neetha.You have explained it in simple way and understandable.Thank you for your information.I do have a question ,before my diabetes was detected ,I used to have a fast and sudden pulling like or a reaction in left eye .I used to be awake all of a sudden even midnight.Later as I was put on medicament .It was reduced or almost disappeared.What can be cause of this?Is it a nerve disorder ?Or on the way to Glaucoma ?I do go for tests regularly as it is prescribed for diabetics.Wish if you could explain this -Thank you

  • mohan prabhu, mangalore/canada

    Thu, Mar 16 2023

    Thank you very much, Dr. Neetha for the very informative Q&A on Glaucoma, its causes, treatment and ongoing/permanent need to keep the eyepressure under constant vigilance and control. I know nothing about opthalmology, leave aside medicine, but do have glaucoma in both eyes and have had it for twenty years now, have been operated locally at the University of Ottawa Eye Institute Glaucoma Clinic in 2023 and again in late October last year in one eye, the next eye is scheduled in two months. I can still function with one eye that was operated for glaucoma 20 years ago. The other eye which had glaucoma was also operated soon after that, and was again operated last October. The operation scheduled in May this year is for the othr glaucoma operated eye, so that the pressure in both eyes is kept optimal. My question to you is, is an operation needed for an old man like me who is 93 and who has probably not a long time left, when I can still function ewith one eye. 2. I am constantly bothered by floaters which shoot from one eye into the air, but not from the other eye, and more noticeable as they are like beams of light coming out of the eye; during day time, I am also bugged by similar symptoms but they appear like microscopic flies or insects. I told my ophthalmologist about it and he thinks it is what he calls Charles Bonnet syndrome. He says there are a few eye exercises; I have tried them in vain. I think that is a "bull" explanation in my case. Do you, or your colleagues at KMC, have any information about this and how to overcome the floaters. I use eye blinders at night for that eye and, of course, soon fall asleelp. Kindly email me at Thank you.

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