Ophthalmologist visits are usually predictable. You expect an eye chart test, a few eye drops, light sensitivity, and an afternoon of temporarily blurry vision. It’s a small price to pay to know your vision is healthy. But have you ever stopped to ask: Why do eye doctors dilate your eyes?

As it turns out, many eye problems can be detected early through eye dilation. So, you might want to reconsider the next time you tell your eye doctor you don’t want to dilate your eyes.

Why Does An Optometrist Conduct A Dilated Eye Examination?

Dilating your eyes with eye drops is an important step when it comes to vision testing, because it allows your eye care professional to see inside each eye.

Pupil dilation allows more light into the center of the eyeball, giving doctors the chance to assess the function of the important tissues in the back of your eye, including your optic nerve, macula, and retina.1

Optometrist vs Ophthalmologist

Before your eye exam, it’s important to know the difference between an optometrist and an ophthalmologist. An optometrist is a medical care professional who specializes in eye care and has attended optometry school. An ophthalmologist is a medical doctor who specializes in the treatment of eye disorders and disease.2

Both ophthalmologists and optometrists are qualified to perform eye exams, but an ophthalmologist is trained to treat a wide range of eye diseases and can perform eye surgery, if necessary.

How Do Eye Drops Dilate Your Eyes?

Now, there are often three different eye drops used during a comprehensive eye examination, and they serve two different purposes.

Cycloplegic Drops

These drops temporarily paralyze the muscles of your eye so that you are not in control of your eye focus. This allows for a procedure called a cycloplegic refraction to take place.

Cycloplegic refraction allows your eye doctor to measure how much help your eyes need (how strong your glasses prescription will be).3

Cycloplegic refraction is common and extremely effective when testing young children, as their eye muscles can easily compensate for vision issues at a young age, hiding potential issues during a routine visual field test.4

Dilated EyesDilating Eye Drops

These eye drops enlarge the pupil and allow the examination of the macula, optic nerve, and retina. This enlargement of the pupil is referred to as mydriasis. The ingredient to dilate your eyes is most commonly phenylephrine.

Phenylephrine, which is also found in decongestants, causes the blood vessels in your eye to constrict and the muscles to relax. This allows your eye doctor to have a clear view to the back of your eye during an exam.5

Miotic Eye Drops

These eye drops tighten the muscles that make your pupil constrict and relax the ones that focus the lens of your eye. This effect is called miosis. You’ve likely experienced miosis before – it occurs naturally when there’s a lot of sunlight or bright light hitting your eyes.

Miotic eye drops are common when treating glaucoma, and are used both in appointments and as part of your at-home care.6

How Does Pupil Dilation Help In Detecting Vision Problems?

Each part of your eye has a specific function, and dilating your eyes is the most direct way to observe macular function. While the blurred vision side effect can be annoying, dilation is a key step in vision screening.

When your eyes are dilated, you’ll experience light sensitivity. This is because your pupil’s job is to regulate the amount of light that passes into your eyes.

When your pupil is dilated, light passes all the way through your eye, allowing your eye doctor to better observe the functions of your retina and macula – the area near the center of your retina that allows you to see sharply.7

Reasons To Dilate Your Eyes

With your pupil fully dilated, a doctor can screen your eye for possible visual issues and overall eye health. All diagnosis, however, stem from two main ways to diagnose. Both ways involve eye drops for dilation.

Retinal Examination:

Your retina is a thin membrane located at the back of your eyeball. When your retina functions properly, it converts the light that comes through your cornea into nervous system messages for your brain. The retina sends these messages to your brain through your optic nerve.8

Macular Examination:

The macula is located in the center of your retina, and it controls central vision skills, like reading and facial recognition. This part of your eye can become weak and stop functioning with age, or as a side effect of health issues like diabetes.9

Dilated Eyes

Tests Involving the Cornea

Your cornea is the outermost lens of your eye. It controls your ability to refract light, so your retina can send it to your brain. When your cornea becomes thin or misshapen, it can require an eyeglass prescription or surgical intervention. Contact lenses are unable to rest correctly on the eye’s surface when a cornea’s shape changes too aggressively.10,11

One common screening for the cornea is tonometry. This procedure measures the amount of pressure in your eyes.

Now, your eye pressure can fluctuate as you age, or because of certain medical issues.

When your intraocular eye pressure is elevated, you will experience a gradual loss of sight. This condition is called glaucoma. Reading your eye pressure accurately can be difficult because everyone’s cornea differs in thickness. Corneal thickness directly affects the internal pressure, but it can be assessed by a quick test called pachymetry.12

Glaucoma is a condition that develops as you age, and is commonly screened in all people over 60 years old. Certain factors, like your gender or ethnicity, can lower your age for glaucoma screening to 40.13

Retinal Detachment: How and Why Does It Happen?

When small holes or tears occur in your retina and allow too much light to reach your optic nerve at one time, it is called retinal detachment. Symptoms include ‘floaters’ and blurred vision, and the condition can result in permanent blindness if left untreated.

The most advanced way to view the health of the retina is to use retinal imaging. Retinal detachment is a serious medical emergency and should receive attention from a medical doctor immediately.

People who are at risk for retinal detachment include:

  • People who are extremely nearsighted
  • Families with a history of retinal detachment
  • Victims of head trauma
  • Those experiencing complications from other ocular health issues, like glaucoma
  • Someone recovering from ocular surgery, like the treatment of cataracts
  • Anyone who has retinal detachment in their other eye14-16

Detached retinas can be rebuilt or patched through a wide variety of surgical options, depending on the severity of the retinal tear or separation.17

Dilate Your Eyes Against Age-Related Macular Degeneration (AMD)

When the macular part of the retina begins to break down, it is called macular degeneration. Now, there are multiple reasons why this can occur, with the leading cause being age. Other reasons include gender, race, and eye color.18

Dilated EyesAs it turns out, age-related macular degeneration (AMD) is a leading cause of blindness in the elderly. In addition, high blood pressure, smoking, and poor diet have been linked to raising your risk of macular degeneration.19,20

Can You Prevent Macular Degeneration?

Obviously, macular degeneration is something you want to avoid. While you can’t control aging, studies suggest you can make certain lifestyle modifications that might help lower your risk of AMD. If you smoke, quit. And watch your weight – obesity is a potential risk factor as well.

Additionally, research suggests a diet low in fat and high in green vegetables may help slow or reverse macular degeneration, as well as a diet high in antioxidants.21

Vision and Diabetes

People with diabetes are at a higher risk of vision problems, as diabetes slowly shuts down the functionality of our organs and extremities.

Specifically, diabetic retinoplasty occurs when the blood vessels in the retina break, swell, and leak due to high blood sugar levels.22

Diabetics who are affected by diabetic retinoplasty report periodic blindness, floaters, and increased trouble with peripheral vision, finding things on shelves, and driving. This increased impairment is caused by the retina losing contact with the optic nerve over time.23

Healthy Vision and Preventative Care

While there are many vision issues that are complex or rare, most problems can be detected and resolved during routine comprehensive eye examinations.

Start practicing vision screening at a young age to maintain great eye health and, as you age, don’t put off that eye exam. Yes, having a dilated eye exam can cause light sensitivity, but it’s nothing a great pair of sunglasses can’t fix!

Learn More:
These Are the Telltale Signs You Need Glasses
Color Blindness: What Is Color Vision Deficiency?
What Are Eye Floaters and How to Protect Your Eyes