Eye Chat with Perak’s Only Fellowship-Trained Retinal Surgeon, Dr. Lee Mun Wai
What you should know about “Eye Stroke”
Most people are familiar with the term “stroke” which refers to a blockage of blood vessel(s) in the brain resulting in partial paralysis, slurred speech and even death in the most severe cases. Not many people however, are aware that the eye itself can also have a “stroke”. The eye is like a camera; light is focused by the cornea and lens onto the “film” of the eye – the retina. The retina is responsible for converting light energy into electrical impulses which are transmitted to the brain and interpreted as images. That is how we “see”!
Like any other tissue in the body, the retina is dependent on nutrients and oxygen from a series of blood vessels comprising of arteries and veins. When blockages (occlusions) occur in these blood vessels, the result is a “stroke of the eye”.
People with eye stroke usually have little warning when it occurs. They could go to sleep with normal vision and wake up with loss of vision in one eye. There is no pain at all and some people notice a dark area or shadow which affects the upper or lower half of their vision.
Types of Eye Stroke
Blockages can occur in either the arteries or veins of the retina. The extent of visual loss depends on whether it is the central or branch artery (or vein) which gets blocked. Artery occlusions are usually caused by a clot or plaque (embolus) which breaks free from the major artery in the neck (carotid) or the valves or chambers in the heart. The embolus may be very small and not cause any significant interruption of blood flow in the larger arteries but when they reach the retina where the vessels are so fine, that’s where the occlusion occurs.
Vein occlusions are caused by a localized clot (thrombus) which forms as a result of hardening of the artery adjacent to the vein. The arteries and veins of the retina are crossing over one another and it is at these crossings where vein occlusions can occur.
The occurrence of an “eye stroke” is often an indication of more widespread vascular disease in the body. The major risk factors are age, high blood pressure, high cholesterol, diabetes and heart disease. A referral to the cardiologist to look for abnormalities in the heart as well as narrowing of the carotid arteries is often necessary. In vein occlusions however, raised pressure in the eye (glaucoma) can also be a risk factor. In artery occlusions, treatment in the acute stage may involve lowering the eye pressure with medication or sometimes by releasing fluid from inside the eye and ocular massage. This has limited success but may help to dislodge the clot and allow normal blood flow again.
In vein occlusions, depending on the amount of bleeding and swelling in the central retina (macula), laser treatment can be done. More commonly now, an injection of a medication which is an anti-VEGF, is given directly into the eye. VEGF is a growth factor which is found in abundance in a vein occlusion and is responsible for causing the retinal swelling and bleeding.
Eye stroke is a potentially devastating eye disease and is often related to other vascular problems in the body. It is therefore, very important that if you have any sudden vision loss, you should visit your ophthalmologist immediately. It is also vital that if you have any risk factors for eye stroke such as hypertension, diabetes or heart disease, that these conditions are well controlled.
For more information, contact: Lee Eye Centre Ipoh
Tel: 05-254 0095 or email: email@example.com. Website: www.lec.com.my