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When you are diagnosed with high blood pressure, your doctor may wish to examine your eyes or refer you to a specialist clinic. A simple test can look at the small blood vessels in the back of your eye, to check if any damage has been done by high blood pressure.
Looking at the back of the eye reveals whether or not your small blood vessels (caplliaries) have thickened, narrowed or burst. This is the only place where the small blood vessels can be viewed and often any problems here are repeated in the small blood vessels in places that cannot be seen, such as in the kidneys.
In fact, many people discover they have high blood pressure because their optician notices the signs during a routine eye test.
How is an eye test carried out?
Before your doctor tests your eyes, he or she will give you eye drops to widen your pupils. This will give a better view of the back of your eye. The drops may sting at first, and may also leave your vision blurry for some hours afterwards. You may also have a medicine taste in the back of your mouth.
The eye test is then carried out by a doctor or ophthalmologist using a handheld machine called an ophthalmoscope. The ophthalmoscope shines a light on the back of your eye, allowing your doctor to examine the blood vessels using magnifying lenses.
Because a bright light is being shined into your eye, you may be temporarily dazzled and may see images of the back of your eye reflecting in your vision. These are known as after-images and are common and completely harmless.
What do I need to do before an eye test?
Before being having an eye test, it is important to say if you:
- are allergic to any medicines
- are taking any medicines
- have glaucoma or a history of glaucoma.
Because the eye drops can make your vision blurry, you may need someone to drive you home. Also, because your pupils are wider than normal, take sunglasses or tinted lenses to wear after the test. After a few hours the effects will wear off and your eyesight will return to normal.