why do they dilate your eyes during an 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.
A thorough, dilated exam allows your ophthalmologist to do a complete exam of the retina, and that is important to do throughout your life, as several eye diseases and conditions are detected at their earliest stages during a thorough eye exam: Prescription Only? On the other hand, of the University of Utah s Moran Eye Center notes, Dilation isn t always required. In fact, if you are seeing your eye doctor solely to get a prescription, dilation induces potential changes to a prescription that aren t present in the normal state of the eye when the iris/pupil is not dilated. The exception is when we re examining young children. We dilate because they have a greater capacity to accommodate and to allow the doctor to use an objective measure to confirm their prescription (i. e. retinoscopy) if they re not very cooperative. Of course, it s always important to dilate if we want to do a complete exam of the retina. Factors your eye doctor considers when determining whether eye dilation is necessary: Age. The risk of eye diseases increases with age particularly over age 40. Eye health. If you ve experienced eye diseases that affect the back of the eye, such as retinal detachment, you may have an increased risk of future eye problems.
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