Why should I get my eyes dilated?

January 7, 2016 - 3 minutes read

Many of our new patients at Cannon EyeCare seem surprised when we bring up dilation at their routine eye exams. Often they have never had their eyes dilated in the past, or it has been a very long time. This blog post will let you know what it means to get dilated, and why it is important.

The right eye is normal while the left eye is dilated

This patient’s left eye has been dilated making her pupil huge compared to the right (undilated) eye.

Dilation means putting in special eye drops that make your pupils huge (see photo above, where the left eye only is dilated). Typically both eyes would be dilated with pharmaceutical drops that cause the pupil to open as the iris retracts. Without dilation your eye doctor’s view of the back of your eye is limited; as they shine light in, the pupil constricts. In most patients the doctor can see about 10-20% of the retina without dilating. When they perform a dilated eye exam, your eye doctor can see the remaining ~85% of your retina. They also get a better look at the crystallin lens (where cataracts occur) and the vitreous (where floaters are located). So in the end you get a more thorough health exam for your eyes. That is the good part.

The down side to having your eyes dilated is that your exam takes longer, there are some bright lights that are uncomfortable, and then there are the side effects. When you get your eyes dilated, the typical side effects include blurry vision that is typically worse up close than far away, in addition to light sensitivity. Both of these side effects can last from 3-6 hours, so getting dilated and then going back to work may not be the best plan. It can also dangerous to drive while dilated, so we always encourage patients to bring a driver if they need to have their eyes dilated.

At Cannon EyeCare we are very thorough, but most of our patients do not need a dilation every year. Most healthy, normal patients are dilated every two to four years. Those with risk factors for vision loss like diabetes, glaucoma, or macular degeneration are dilated more often. If you have trauma to an eye or experience new floaters or flashes of light, you should go see your eye doctor and ask to be dilated right away. New floaters and flashes of light can sometimes be due to a retinal tear or detachment. So if you are diabetic and are due for dilation or have had a recent onset of flashes and/or floaters, call your eye doctor today to make sure your retina is OK.

Sincerely, Dr. Mark Cannon, optometrist @ Cannon EyeCare (at Market Optical) in Seattle, Washington

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