Transient Monocular Blindness
A flash of lightening pierces the sky! You know you are in for a wet time if you don’t find a dry haven soon. A clap of a loud thunder follows. You embrace yourself, and sure enough, a torrential downpour lashes from the skies. What if you could prevent the impending rainstorm as soon as you saw the lightening? Impossible, right? However, transient monocular blindness, like the lightening, is a harbinger of the major disease - stroke. And what’s better, if you act in time, the stroke is not always inevitable.
Transient Monocular Blindness, also called as Amaurosis Fugax is a condition in which there is abrupt loss of vision in one of your eyes due to a temporary lack of blood supply to your retina (light sensitive layer in your eye).
Transient Monocular Visual Loss is mainly caused by lack of blood supply. This may be due to:
• Blocking of the artery supplying your brain (called carotid artery) or eyes (called ophthalmic artery) due to a blood clot or fatty substance (called plaque).
• Narrowing of the blood vessel supplying your brain with brief drop in blood pressure.
• Impending closure of circulation of the optic nerve (nerve supplying your eye) or retina.
• Swelling of your optic disc (the part where the optic nerve enters your retina).
• Sudden constriction of the small arteries of your retina.
Risk factors for developing blockage or narrowing of blood vessels include having raised cholesterol, high blood pressure, heart disease, smoking and diabetes.
There is sudden loss of vision. This may be seen as a gray black curtain that falls slowly on your field of vision. The episode is entirely painless.
The episode generally lasts for a few seconds. It may remain for several minutes sometimes. Vision returns to normal after this.
Complete Eye Examination which may show a clot blocking the retinal artery
Thorough Neurological Examination as this symptom may precede a stroke.
A carotid artery ultrasound or MRA (magnetic resonance angiography) scan should be done to evaluate the blockage.
Tests are needed to assess your risk factors like blood sugar and cholesterol.
The treatment of Transient Monocular Visual Loss varies depending on the severity of your blockage. The main aim of treatment is to prevent a stroke. You may be advised:
• No immediate treatment other than regular check up to keep a watch on your carotid artery.
• Modifications in diet and lifestyle along with medications to control your blood pressure
• Blood thinning medications to decrease your risk of stroke
• Carotid Artery Surgery (called Carotid Endarterectomy) may be required to remove the blockage in your arteries
Amaurosis fugax itself does not usually cause any permanent disability. However, it does put you at a greater risk for a stroke which can lead to permanent and severe disabilities.
Transient Monocular Vision can be prevented by preventing the buildup of blockages in your arteries and taking care of the risk factors. Some general guidelines are:
• Restrict alcohol intake.
• Exercise for at least 30 minutes every day.
• Quit Smoking
• Avoid fatty foods
• Keep a control on your blood pressure every 1 – 2 years and try to maintain it around 120-130/80 mm hg.
• Have your cholesterol levels checked at least every 5 years.
• If you have diabetes, high blood pressure, heart disease or a positive family history of these, you will need a check on a more regular basis.