Why Do You Need Your Eyes Dilated for Eye Exams?
Reading an eye chart at your eye doctor’s office to help test for refractive errors is important, but it is just one of many tests your eye doctor uses to determine your overall eye health.
Examining the interior structures of your eye for signs of disease is also essential, particularly to check for retinal diseases and determine the health of your optic nerve located at the back of your eye. To adequately view the interior of your eye, your doctor will need to dilate your pupils so there is a wide enough opening to conduct a comprehensive eye exam. In this blog post, we will explain the importance of dilating your pupils for an eye exam and provide general tips on how to care for your eyes after dilation.
Dilating Pupils for an Eye Exam
Under natural conditions, your pupil, the dark circle in the center of your eye, does not open wide enough, or allow enough light in, to enable your eye doctor to see the back of your eye. This is due to a protective measure called the pupillary response in which the pupil constricts in response to bright light.
The smaller the pupil becomes, the harder it is for your eye doctor to see the back of your eye.
“The pupil acts like a window to allow me to look in the back of the eye. When that window is opened wider, I get a much better field of view,” said Dr. Jessica L. Lucas, an optometrist at the Dean McGee Eye Institute.
To counteract the natural tendency of the pupil to constrict, special eye drops are used to dilate the pupil and keep it wide for the exam.
Eye Dilation Drops
The iris, the colored part of your eye, contains muscles that regulate the amount of light that enters your eye by expanding and contracting the size of your pupil.
Eye dilation drops stimulate your pupils to open wide, allowing in more light for the exam. There are two types of drops that are used. One type, such as phenylephrine, stimulates the muscles so your pupils widen. The other type, such as tropicamide, relaxes the muscles so your pupils do not contract. They are often used together or in a combination eye drop.
Administering eye dilation drops is relatively painless. You usually have to wait about 20 or 30 minutes for your eyes to become fully dilated. This process is quicker if you have blue, green, or hazel eyes. Once dilated, your pupils become large enough for your eye doctor to examine the interior structures of your eye, including your retina and optic nerve, using different techniques such as indirect ophthalmoscopy or a slit lamp.
In indirect ophthalmoscopy, the doctor uses a headset with a light source and binocular lenses (similar in appearance to a miner’s headlamp) along with a handheld lens to magnify and view the image coming from inside your eye. A slit lamp is a type of microscope with a narrow beam of light, which can also be also be used in conjunction with a handheld lens to view the back of your eye.
What Not to Do After Eye Dilation
Because eye dilation widens your pupils more than normal, your vision will be blurry — especially when viewing things close up — and you may be sensitive to light.
The blurriness and sensitivity to light may cause problems driving. Consider having a friend or family member drive you to and from your appointment.
Avoid spending time in the sun as your eyes are more at risk from UV damage because your pupils will not constrict as normal. Should you go outside, wear sunglasses to prevent damage from UV rays.
Blue light emitted from electronic devices can also impact your eyes when dilated. Try limiting your time spent in front of a computer screen or phone. Watching TV is fine because you are likely sitting far enough away. Avoid reading small text as the strain from your blurred vision could cause headaches.
How Long Does Eye Dilation Last?
The range in time for your pupils to return to normal depends on many factors, including age and eye color. Light-colored eyes, such as blue or hazel, may take longer to return to normal.
Generally, light sensitivity and blurred vision go away after a few hours, although it can take up to a day for your pupils to return to normal, which is why you should take the extra precautions mentioned above.
How Often Should You Get Your Eyes Dilated?
How often you should have your eyes dilated depends on several factors. You should have a dilated eye exam once every year or two, especially if you are over the age of 60, are an African American over the age of 40, or have a history of eye issues, such as a retinal detachment or a family member who has had glaucoma.
People with diabetes or high blood pressure should have their eyes dilated each year as these conditions can damage the tiny blood vessels of the retina and lead to blurred vision or loss of sight.