Alamo Optometry Blog

September 7, 2014

Why Do I Need to Get My Eyes Dilated?

Filed under: Uncategorized — gkblog @ 5:32 pm

(As appeared in Alamo Today, May 2014)

As you can imagine, I get this question at the office on a daily basis.  Most patients understand that it is part of the comprehensive examination, but they don’t always know the reasoning behind it.  Therefore, they are always trying to get out of doing it.  The dilation is a very important (some would argue the most important) part of the exam, which helps determine the status of your ocular and systemic health.

The most valuable asset of the retina is that it is the only place in the body where neural tissue (the optic nerve and retina) and blood vessels can be directly viewed without an invasive procedure.  Trying to evaluate the retina through an undilated pupil is very difficult because as light is used to see into the eye, the pupil constricts to a pinhole.  Looking through a very small aperture does not allow the entire retina to be viewed.  The dilating drops will open up the pupil and will not allow it to constrict.  Since the muscles within the eye control the focusing power of the eye and the opening and closing of the pupil in response to light levels, paralyzing these muscles is why patients will experience light sensitivity and poor reading for a few hours after the drops are instilled.  The typical timing for the drops to wear off is between 2 and 3 hours.

A dilated examination can both diagnose and evaluate the progress of many systemic diseases;   in addition, assuring the patient that the eyes and retina are healthy and free of any conditions.  The main ocular conditions found during dilation include cataracts, diabetic and hypertensive retinopathy, glaucoma, macular degeneration, and retinal holes, tears, and detachments.  Systemic ailments such as diabetes, high blood pressure, multiple sclerosis, brain tumors, and heart and carotid artery disease can be diagnosed in the course of a dilated evaluation.  For otherwise young and healthy patients, dilation should be done about every 2 years.  For patients who are diabetic, have cataracts, glaucoma, or are taking certain medications, dilation should be done annually at the minimum.  For these patients, in addition to visiting your internist, endocrinologist, rheumatologist, etc. an annual dilated examination should be conducted.  Most physicians realize the importance of dilation and will require it of their patients.  When these patients come into the office, a letter to the doctor will be sent to update him/her on the condition of the eyes.

When an eye professional needs to assess the health of the back portion of the eye, dilation is still the standard of care.  There are new digital imaging systems that take relatively good views of the retina.  However, they are generally not able to reach the far periphery of the retina, and they are only able to give a 2-dimensional view of the retina as viewed on a computer monitor.  Dilation using an instrument called a binocular indirect ophthalmoscope (BIO) allows the doctor to see all around the retina in 3-dimensions.  Keep in mind that although reading ability will be impaired for a few hours, distance vision remains the same.  Light sensitivity might make it harder to see outdoors, but the actual vision does not change.  Please bring your sunglasses with you to the exam; if you don’t own any, we have some shields that will help protect you from the sun.

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