DR Fong: Sudden loss of vision to one of our eyes is one of the most frightening things we can encounter.
This is usually caused by a blockage to one of the main blood vessels of the eye.
This can be loosely called an "eye stroke".
An eye stroke occurs when a clot forms in a small blood vessel within the eye.
The interruption of blood flow destroys the retina, the light-sensitive nerve layer that captures images.
The attack is sudden, painless, but can cause partial or complete vision loss in one eye. The other eye is usually unaffected.
Stroke refers to an acute loss of blood supply to any portion of the brain, resulting in irreversible brain damage and loss of bodily functions controlled by that part of the brain.
The eye is connected to the brain by the optic nerve, which directly comes from the brain.
In fact, the eye is the only part of our body where we can look at our brain directly.
Eye doctors use an ophthalmoscope to look at the optic nerve through the pupil of the eye to look for various eye diseases.
Because of this direct eye/brain connection, stroke frequently affects both vision and the ability to coordinate the movements of both eyes.
So, the term "eye stroke' is actually quite accurate.
The retina at the back of the eye requires a constant blood supply.
This blood supply makes sure that the cells of the retina get all the nutrients they need to continue working.
The blood supply also removes any waste material that the cells have finished with.
Like the rest of the body, there are two types of blood vessels concerned with the blood supply to the retina; arteries and veins.
Arteries carry fresh blood from the heart and lungs to all the cells in our bodies.
Veins take away the blood that has been used by the cells and return it to the lungs and heart to be refreshed with oxygen and other nutrients.
When the arteries become blocked, then this fresh blood cannot reach the cells and the retinal cells quickly suffer from the lack of oxygen.
This stops them working and sight can be affected quite badly.
The amount of sight that is affected varies according to the location of the blockage.
We can imagine our blood vessels spreading across the retina like a tree.
Thinking of them like this helps in understanding how much sight is affected by an artery occlusion.
The retinal arteries have a large trunk of a blood vessel that splits into smaller branches to feed all parts of the retina.
If the trunk of the tree is blocked then a lot of sight will be affected; less sight will be affected if the blockage happens further along in one of the branch arteries.
The main cause of a retinal artery occlusion is atherosclerosis.
Atherosclerosis is a problem with the condition of the inside of the blood vessel's wall.
Our blood vessels are like a tube with the blood flowing through it.
The tube is usually wide and smooth so that the blood flows directly through it.
However, in some people, the inside of this tube becomes thinner or sticky, which means it is harder for the blood to flow through it.
These patches of sticky blood vessels are called atherosclerotic plaques.
Problems occur because these sticky patches can catch any debris in the blood, which in turn makes the plaques bigger.
If the plaques become bigger, they can cut off part or all of the blood going to or from the retina.
Large pieces of debris can also get caught and block off the blood vessel, leading to an artery occlusion.
A rare cause of retinal artery occlusion is a giant cell arteritis, which is a disease where the blood vessels are blocked due to inflammation of the blood vessel wall.
This needs treatment with steroid tablets or injection.
Eye stroke is an emergency and needs immediate attention by an eye doctor to determine whether it is an artery or vein occlusion.
Unfortunately, there is little treatment available for retinal artery occlusions because the cells on the retina are very sensitive to a lack of blood supply.
A disturbance for any length of time in the supply of fresh blood to the retinal cells will cause permanent sight loss.
There are a number of common risk factors for eye stroke.
They are quite familiar since these same risk factors can cause other problems like heart attacks and brain strokes.
The main risk factors are:
- Age - most eye strokes happen in people over the age of 50 years
- High blood pressure
- High cholesterol levels
Although nothing can be done about our age, all the other risk factors can be controlled.
Regular visits to your family doctor to diagnose problems like high blood pressure and cholesterol levels, good diabetic control, a healthy diet, and stopping smoking can all help to reduce the risk of getting an eye stroke.
What concerns me is that I am seeing more patients with eye stroke who are younger than 50 years old.
This suggests that the general well being of the population in terms of blood pressure control, high cholesterol levels, and diabetes incidence, is getting worse rather than better.
My colleagues in the UK have found that more than 12% of patients who presented with eye stroke went on to suffer a stroke or heart attack within two years, and 70% of these patients had the stroke or heart attack within two months of the loss of vision.
What this means is that getting an eye stroke is an indicator of future severe life-threatening events, and the patient needs to have their general medical condition reviewed and have all their potential risk factors treated adequately.
Being male and having high blood pressure puts you at much higher risk of getting a full blown stroke or heart attack after getting an eye stroke.
An eye stroke is a shock to most people.
At first, you may find that you are constantly aware of the change in your vision and that the sight loss in one eye dominates your vision, making it difficult to see using both eyes.
However, after a few months, you will probably find that this becomes less of a problem.
This happens because our brains are able adjust to a new level of vision and are able to make the eye with good sight the dominant one.
Usually, people find that with time their good eye "takes over" and that tasks that were difficult become easier.
When sight in one eye is affected, it can affect our depth perception. You may find that you have trouble judging distances, how high a step is, or how far away a table is.
With time you should be able to judge these distances better, but you should take care in the first couple of months.
Chui Hoong: What you eat can modulate your risk factors for eye stroke. Your healthy diet should incorporate the following:
1. Fat intake
Cut back on total fat intake.
Choose healthier cooking methods.
Reduce saturated fat and trans-fat intake. These are found mostly in animal fats (eg fatty cuts of meat), processed foods (sausages, burgers), baked goods (cakes, cookies, pastries, pies) and coconut milk.
Replace the saturated or trans-fat with unsaturated fat sources (eg oily fish, nuts).
2. Fruits, vegetables, wholegrains and pulses
Increase fruit, vegetable, wholegrains and pulses intake.
They are good sources of total and soluble fibre, and rich in antioxidants.
Fruits and vegetables are also good sources of potassium, which helps to lower blood pressure.
Five portions of fruits and vegetables a day is hardly enough.
You should aim to get more than seven portions a day!
3. Maintain a healthy body weight
As a guide, Malaysians should aim to have a body mass index of 19-23.
I have included a simple breakfast recipe that uses oats and is naturally sweetened with fresh fruits.
Breakfast is an important meal and it helps in weight management.
Dr Fong Choong Sian is a consultant ophthalmologist while Goo Chui Hoong is a consultant dietitian. They are publishing a book on eye health and diet next year. For further information, e-mail email@example.com. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader's own medical care.