The silent stealer of vision; A review of the commonest cause of irreversible blindness
How would you feel if you woke up one day and had suddenly lost your vision?
Or you then begin to lose your vision in a rapid manner?
In a previous post, I talked briefly about my ophthalmology posting as a medical student. I mentioned that I had encountered some patients who were practically blind. I did mention a few causes back then and one of them was glaucoma.
Of all the causes of blindness, glaucoma was the one I disdained the most for a number of reasons. One was that it was irreversible and had no cure. Another reason was that it gradually takes away a person’s sight sometimes without the person even knowing until it is well advanced.
Interestingly, glaucoma is the second leading cause of blindness worldwide according to WHO. This means that anyone can be affected and that is even more reason why the public should be educated on this so as to be able to tackle it early and curb its growing menace.
What is Glaucoma?
Glaucoma refers to a group of eye conditions that damage the optic nerve( the nerve responsible for sight).
I remember while growing up and seeing my grandmother blind. At that time, I thought blindness was a total loss of vision.
However, I discovered that she could see me doing some things and at some point, she would report some of my wrong deeds to my mother.
This got me confused for a while but as you read on you will understand what happens when glaucoma affects the eye.
By National Eye Institute, National Institutes of Health (TIFF image), Public Domain, Wikimedia The picture above shows the way a patient with glaucoma sees. This is called tunnel vision as there is loss of peripheral vision meaning you can only see centrally
By National Eye Institute, National Institutes of Health (TIFF image), Public Domain, Wikimedia
What are the causes of glaucoma?
Within the eye, there are different compartments. These compartments have fluids that are continuously secreted and drained.
The aqueous humour is the fluid in the anterior part of the eye. It is being produced by an organ called the ciliary body and drained by a meshwork called the trabecular meshwork and minor drainage called the uveoscleral outflow.
When there is excess production or reduced drainage, pressure builds up. If for anything there is no balance, pressure builds.
This pressure affects the surrounding structures of which the optic nerve( you remember it) is primarily involved.
This is why if it’s caught early, additional vision loss could be prevented.
Glaucoma is usually but not always, the result of abnormally high pressure inside the eye.
Other causes could be familial, age and sometimes race.
What are the symptoms of glaucoma?
Glaucoma is called ‘the silent thief of sight’ because it usually has no symptoms in its early stages especially in types like open-angle glaucoma.
It's that bad that half the people with glaucoma do not know they have it!
However, the symptoms depend on the type of glaucoma.
What are the types of glaucoma
Let's get something straight...
The drainage system is angulated and if the angle gets smaller such that there is difficulty with drainage, glaucoma ensues
This drainage can get blocked too and we can guess what will happen.
It is worth noting that there are different things that can make the angle reduce.
So now the types...
Open-angle (chronic) glaucoma:
This is the most common type of glaucoma. In this case, nothing happens to the angle and there are no warning signs or obvious symptoms in the early stages.
As the disease progresses, blind spots develop in the peripheral (side) vision as well as gradual vision loss.
Therefore, open-angle glaucoma is a cause of gradual loss of vision and this was why my grandmother could still see me. Her central vision was still preserved.
Angle-Closure (Acute) Glaucoma:
If the flow of aqueous humour fluid is suddenly blocked, the rapid build-up of fluid may cause a severe, quick, and painful increase in pressure.
Angle-closure glaucoma which is also known as narrow-angle glaucoma is an emergency situation. It can present with symptoms such as:
- severe eye pain
- sudden blurred vision
- redness in the eye
- sudden vision disturbances
- seeing halos
Secondary glaucoma is often a side effect of injury or another eye condition, such as cataracts or eye tumours. Medicines, such as corticosteroids, may also cause this type of glaucoma. Rarely, eye surgery can cause secondary glaucoma.
In some cases, people without increased eye pressure develop damage to their optic nerve. The cause of this isn’t known. However, extreme sensitivity or a lack of blood flow to the optic nerve may be a factor in this type of glaucoma.
In pigmentary glaucoma, pigment granules from the iris build up in the drainage channels, slowing or blocking fluid exiting the eye.
Activities such as jogging sometimes stir up the pigment granules, depositing them on the trabecular meshwork and causing intermittent pressure elevations.
Some people may see halos or have blurry vision after activities like jogging or playing basketball.
Glaucoma can affect any age group and some babies are born with this condition. When this happens, it is called congenital glaucoma.
Children born with congenital glaucoma have a defect in the angle of their eye, which slows or prevents normal fluid drainage.
Congenital glaucoma usually presents with symptoms such as cloudy eyes, blepharospasm (excessive involuntary closure of the eyelids), epiphora (excessive tearing) or photophobia (sensitivity to light).
Who are the people predisposed to having glaucoma?
The first set of people are those who have high internal eye pressure (intraocular pressure), those over 60 years of age.
A positive family history of most conditions always predispose one to that condition and glaucoma is not exempted.
Being black, Asian or Hispanic is another risk factor.
There are certain medical conditions that predispose one to high intraocular pressure and others that affect the blood vessels. Conditions like Diabetes, hypertension and sickle cell have been implicated as risk factors for glaucoma.
Other things that put you at risk include;
- Having corneas that are thin in the centre
- Being extremely nearsighted or farsighted
- Having had an eye injury or certain types of eye surgery
- Taking corticosteroid medications, especially eyedrops, for a long time
How can glaucoma be caught early?
By NIH - , Public Domain, Wikimedia
As earlier stated, early detection and prompt treatment can help reduce the progression and this is why it is important to see an eye doctor once in a while say 6months.
Diagnosing glaucoma involves taking a detailed medical history to exclude risk factors and characterize the symptoms
The most important aspect of diagnosing glaucoma is by measuring intraocular pressure (tonometry). This is such an easy test. It's cheap and it doesn't take time.
I am sure if you have visited an eye clinic, a doctor must have looked into your eye with an instrument that has a light. This is called fundoscopy and this helps to look at the optic nerve and see the extent of the damage.
In glaucoma, there is loss of peripheral vision meaning that you might not be able to see side views without having to turn towards that side. Another way of seeing the extent of damage is by checking for areas of vision loss (visual field test)
Other ways of diagnosing glaucoma include;
- Measuring corneal thickness (pachymetry)
- Inspecting the drainage angle (gonioscopy)
Can glaucoma be treated?
From the cause of glaucoma, treatment is focused on reducing intraocular pressure which in turn halts further vision loss.
Depending on the situation, treatment may be medical or surgical or a combination of both.
Most times, glaucoma treatment often starts with prescription eye drops. These can help decrease eye pressure by improving how fluid drains from the eye or by decreasing the amount of fluid the eye makes.
Prescription eye drops include Prostaglandin analogues, Beta-blockers, Alpha-adrenergic agonists, Carbonic anhydrase inhibitors, Rho-kinase inhibitors or Miotic or cholinergic agents. Just meet your doctor, he will do the needful!
There are times when eye drops alone are not able to bring the IOP down to the desired level(11-25mmHg) the doctor may then prescribe an oral medication which usually has a synergistic effect.
I mentioned that the angle of drainage could get reduced or the drainage itself could get blocked.
If the angle is reduced a surgery can be done to increase the angle so that it can drain properly.
If the drainage is blocked, the cells responsible for producing fluids can be destroyed and most times this is done using a laser.
It should be noted that there’s no cure for glaucoma, and life-long treatment may be needed to regulate the IOP.
Unfortunately, vision loss as a result of glaucoma cannot be restored hence the need for prevention.
How can glaucoma be prevented?
Glaucoma can’t be prevented, isn't that sad?
However, it’s still important to catch it early to prevent it from getting worse.
The best way to catch any type of glaucoma early is to have an annual preventive eye care appointment.
Glaucoma is the commonest cause of irreversible blindness
Glaucoma is an eye pathology of which the major problem is an increase in intraocular pressure.
If diagnosed early and treatment is commenced early, the progression slows down
Annual visits to the eye clinic can help in detecting this problem early and treatment could be either medical or surgical.