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What is Eye Dilation and Why is it Important?

Dilation—or the eye drops that sting when put in and make you light sensitive and blurry for a few hours—are something many patients dislike about going to the eye doctor. Why do eye doctors want us to undergo this eye torcher?


What is Eye Dilation?

Dilation is typically performed by instilling a drop of Tropicamide into the eye. Tropicamide is a cholinergic antagonist, meaning it inhibits the muscarinic receptors of the sphincter muscle of the iris.

What does that even mean? To break it down to a little more understandable language, a cholinergic antagonist is a drug used to inhibit the parasympathetic nervous system—or the controler of the “rest and digest” system.

In the eye, the parasympathetic nervous system controls the iris sphincter muscle—a muscle in the eye that constricts the iris (the colored part of your eye) to make your pupils smaller to help view objects up close.

Therefore, Tropicamide (or any cholinergic antagonist) temporarily inhibits this function—meaning the pupil of the eye stays big instead of small.


Why is Eye Dilation Important?

An essential part of any eye exam is for your eye doctor to get a good view of the back structures of the eye—the retina—to get a good health check.

To see the back of the eye, your doctor needs to use a series of lenses to look through the pupil and into the retina. The smaller the pupil is, the more difficult it is to see back into the eye, and the more limited of a view your eye doctor will get.

Think about this as the pupil being a keyhole. When you peak through a keyhole you have a very small, limited view of what is on the other side. Dilation drops turn the “keyhole” into a window and thus provide a bigger area to view through.


But Why Exactly do Eye Doctors Care so much about the Retina?

Believe it or not, the retina is the only part of the body that doctors can physically look inside without surgery. Optometrists can see arteries and veins and any of the diseases that go along with these structures.

The retina also connects to the brain through the optic nerve head, allowing for even further evaluation of issues that occur in the central nervous system.

Besides being an important indicator for your overall systemic health, the retina is also the most important part of the eye. The retina is filled with special cells called photoreceptors. Photoreceptors are responsible for detecting light and transmitting it to the brain to be turned into images.

Without a healthy retina, you would not be able to see.

Some examples of things your eye doctor can see through carefully examining the retina include:

  • Retinal Detachments
  • Retinal Holes and Tears
  • Macular Edema (Swelling of the retina)
  • Hypertension (high blood pressure)
  • Multiple Sclerosis
  • Variations of Brain Tumors
  • Diabetes
  • Diabetic Retinopathy
  • High Cholesterol
  • Cancer
  • Various Genetic Diseases
  • Glaucoma
  • Macular Degeneration
  • Medication Adverse Reactions
  • Many More!

Many eye doctors have actually been able to save patient’s lives through careful evaluation of the retina to warn patients of stroke or heart attack!

While your eye doctor may not be the doctor you think about first when you hear some of these diseases, optometrists play a crucial role in detecting these subtilities in the retina and referring you to the appropriate doctor for immediate care. All of this medical help is brought to you through a good dilated exam!


What if I Really Do Not Want My Eyes Dilated?

Fortunately with advancing technology there are now retinal cameras that allow doctors to look at the retina without dilation drops. One popular camera is called OptoMap, which can take a picture and allow your doctor to observe up to 200 degrees (out of 360 degrees) of the retina.

Retinal photos are a great tool, they are especially great for doctors to be able to compare photos from year to year to see if anything has changed or is progressing.

However, retinal photos are not a replacement for dilation. It is recommended that if you opt to do photos instead of dilation, that you be dilated the next year—or at least once every 3 years.

It is also always possible that your photo will reveal something your doctor wants to take a closer look at via dilation.

If you take a photo and your doctor asks you to be dilated at that same visit, you should always undergo dilation to allow them a better look.


Our eye doctors at Eye Theory in Houston, TX excel in the prescription of contact lenses, glasses and various eye diseases.  Call our optometrist at 832.831.7386 or schedule an appointment online if it is time for your eye exam with eye dilation.  Our eye doctor, Dr. Jonathan Tsao, provides the highest quality optometry services and eye exams in the Midtown, Downtown, Museum District, Montrose, East Downtown, and Southside Commons (Southside Place) vicinities of Houston, Texas.