The need for eye dilation during an eye exam depends on a variety of factors, such as the reason for the exam, age, general health, and risk of eye diseases. The eye doctor may decide not to dilate the eyes during each exam if there are no risk factors for diseases that dilation may reveal. Dilation allows the doctor to use a magnifying glass to see the inside and back of the eye, including the retina, optic nerve, and blood vessels. Annual exams become important in your late thirties, when changes in vision and concentration are more likely to occur, along with eye diseases.
Eye dilation also causes vision to be blurred and makes the eyes more sensitive to light, which can affect your ability to drive or work for a few hours. If you have new and worrying eye symptoms or vision problems, eye dilation may be needed to make a diagnosis. People ages 20 to 30 should have an eye exam every two years, unless there are changes in vision, pain, flashes of light, new floating particles, injuries, or tearing. Eye dilation rarely causes side effects, although the pupils will remain enlarged for 4 to 24 hours after the exam.
A comprehensive eye exam may be the only way to identify certain conditions early and control them before they seriously affect vision. The test is simple and painless. The doctor will check for vision problems that make it difficult to see clearly and then give you eye drops to dilate (widen) your pupil and check for eye diseases. When more light enters the eyes, the doctor can more easily see the back of the eye and detect signs of numerous diseases or conditions.