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why do they dilate your eyes for eye exam

The eye is a beautiful organ, and it is the only place in the human body where a doctor can see a part of the central nervous system, the optic nerve. The observation of that nerve is a crucial part of a comprehensive eye examination. Both the dilated and the undilated eye exams provide important information to an eye doctor. Let s explore the undilated exam first. The Undilated Eye Exam One of the first parts of a comprehensive eye exam is a test of your vision, and perhaps a measurement to determine an eyeglass prescription, both of which require that your eyes remain undilated. In addition, eye doctors will examine your
responses to light prior to dilation. This can be important for determining whether the visual pathways for each eye are functioning properly. There is also an examination, called gonioscopy, which allows the doctor to examine your eye s drainage angle with a special mirrored lens. The angle that is being referred to is the angle between the iris, which makes up the colored part of your eye, and the cornea, which is the clear window front part of your eye. When the angle is open, your ophthalmologist can see most, if not all, of your eye s drainage system. When the angle is narrow, only portions of the drainage angle are visible, and in acute angle-closure glaucoma, none of it is visible. Part of a glaucoma examination is formal visual field testing, where your peripheral, or side vision, is tested. Ideally, your eyes are not dilated during this test. Finally, there are other parts of the front of the eye, the iris for example, which should be examined when your eyes are not dilated. The Dilated Eye Exam The view to the back of the eye is limited when the pupil is not dilated. When your pupil is small, an eye doctor can see your but the view is limited. In order to see the entire retina, the pupil must be dilated. This is achieved through the use of eye drops. They typically take about 15-30 minutes to fully dilate the pupils, depending the person s response to the medication, and typically take 4-6 hours to wear off.


Onc your eyes are dilated, there is an increase in light sensitivity because the pupil is large and more light is coming through, so bring your sunglasses, or your ophthalmologist may provide some disposable shades for your use. You may also experience blurry vision, particularly if you are trying to read. Some patients feel a tightening or different sensation in their eyelids. If it is your first time having your eyes dilated or you know your vision is too impaired for driving after dilation, bring a friend or companion to drive you home from your examination. While in the past there were some eye drops that could reverse the dilation, these are no longer available, so you will have to wait the 4-6 hours before the drops completely wear off. What Conditions are Diagnosed with a Dilated Eye Exam? Glaucoma The optic nerve can be seen through an undilated pupil, but for optimum viewing a dilated pupil is required. This is important for the diagnosis of, as well as other diseases of the optic nerve. Macular Degeneration Two very common retinal diseases, diabetic retinopathy and (AMD), are diagnosed and monitored by examining the retina through a dilated pupil. Other Conditions In addition to macular degeneration and glaucoma, there are many other conditions that require pupil dilation, such as detection of a retinal tear or detachment, or an ocular tumor, just to name a few. How Frequently Should You Have a Comprehensive Dilated Eye Exam? The National Eye Institute generally recommends that starting at age 60 everyone should have an annual, comprehensive, dilated eye examination. If you are African-American, the recommended age of having a dilated eye exam is 40 years old, because of the higher risk of glaucoma. The American Academy of Ophthalmology has specific recommendations for diabetic patients.


It is recommended that Type 1 diabetics have their first eye exam within five years of diagnosis. Type 2 diabetics, should have their eye exam at the time of diagnosis. If you are a diabetic woman considering pregnancy, it is recommended to have an exam prior to conception or early in the first trimester. Summary As part of a comprehensive eye examination, pupil dilation is very important at revealing the status of your optic nerve and retina, and is critical to preventing and treating eye conditions that could potentially lead to vision loss. You may think your eyes are healthy, but visiting an eye care professional for a comprehensive dilated eye exam is the only way to really be sure. During the exam, each eye is closely inspected for signs of common vision problems and eye diseases, many of which have no early warning signs. Annual comprehensive dilated eye exams are generally recommended starting at age 60. However, African Americans are advised to start having comprehensive dilated eye exams starting at age 40 because of their higher risk of glaucoma. Its also especially important for people with diabetes to have a comprehensive dilated exam at least once aPyear. Key elements of a comprehensive dilated eye examination include, and a. Dilation is an important part of a comprehensive eye exam because it enables your eye care professional to view the inside of the eye. Drops placed in each eye widen the pupil, which is the opening in the center of the iris (the colored part of the eye). Dilating the pupil allows more light to enter the eye the same way opening a door allows light into a dark room. Once dilated, each eye is examined using a special magnifying lens that provides a clear view of important tissues at the back of the eye, including the retina, the macula, and the opticPnerve. This video describes what a doctor sees when examining the retina, optic nerve and macula after the pupils arePdilated.


In a person with diabetic retinopathy, the most common diabetic eye disease and a leading cause of blindness in the United States, the exam may show swelling or leaking of blood vessels in the retina, the light-sensitive layers of tissue at the back of the eye. The eye care professional may also see abnormal growth of blood vessels in the retina associated with diabeticPretinopathy. In age-related macular degeneration (AMD), a common cause of vision loss and blindness in people over the age of 50, the exam may show yellow deposits called drusen or clumps of pigment beneath the retina. In some cases, the exam may also show abnormal growth of blood vessels beneath the retina. These AMD-related changes tend to cause deterioration of a small area of the retina called the macula, which is needed for sharp, centralPvision. A comprehensive dilated eye exam is also critical for detecting glaucoma, a disease that damages the optic nerve, which carries information from the eyes to the brain. In a person with glaucoma, the dilated exam may show changes in the shape and color of the optic nerve fibers. The exam may also show excessive cupping of the optic disc, the place where the optic nerve fibers exit the eye and enter thePbrain. Tonometry is a test that helps detect glaucoma. By directing a quick puff of air onto the eye, or gently applying a pressure-sensitive tip near or against the eye, your eye care professional can detect elevated eye pressure, which can be a risk factor for glaucoma. Numbing drops may be applied to your eye for thisPtest. A Visual field test measures your side (peripheral) vision. A loss of peripheral vision may be a sign ofPglaucoma. A Visual acuity test will require you to read an eye chart, which allows your eye care professional to gauge how well you see at variousPdistances.

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