In 50% of cases, ocular migraines cause temporary and dramatic visual disturbance. In the other half of cases, ocular migraines can cause lesser vision disturbances such as:
Partial vision loss
Scotomas, or a blank spots in your vision
Flashes of light
Ocular migraines are usually brief, lasting less than five minutes. However, they can last up to 30 minutes. Forty-one percent of people have a headache during the vision loss. Twenty-five percent have it before...
The test is painless. To get the scan, you'll lie on a table. You may get a shot of "contrast material" into one of your veins, which will help doctors see parts of your brain more clearly on the image.
Be sure to tell the doctor or nurse if you've had an allergic reaction to contrast material in the past. The dyes have iodine, which can cause a reaction in some people.
The CT scanner uses X-rays, but the amount of radiation you get from them is kept to a minimum. But if you are or think you may be pregnant, let the doctor know -- X-rays can be harmful to a growing baby. A child who needs to have a CT scan should get it at a facility that often works with children, so that the lowest possible dose of radiation can be used.
How Should I Prepare?
Don’t eat anything 4 hours before your test.
Keep taking your medications as usual after you check with your doctor.
Plan for your test to take at least an hour. Most scans take from 15 to 60 minutes.
Ask your doctor any questions you have before the scan.
What Happens Before the Test?
You may get a drug that will make you feel relaxed and drowsy.
You may need to change into a hospital gown, because snaps and zippers in street clothes can interfere with the scan. You also may need to take off your watch, rings, or jewelry. It's a good idea to leave your valuables, including jewelry, at home.