by Todd Childs
Everyone remembers seeing the big “E” at the eye doctor’s office. But if it has been a few years since visiting the doctor’s office, there might be some questions about the process. Let’s talk about what to expect at your eye exam.
Eye exams are an important part of routine body maintenance. These painless procedures help with early detection of eye disease, result in clearer vision and, sometimes, result in new contact lenses. They also offer you a chance to talk with your doctor face to face about eye health issues.
Eye exams are not just for people who want to wear glasses. Eye exams allow doctors to make recommendations for contact lenses as well. Eye care professionals provide reliable information about eye care and can offer basic demonstrations on how to wear and care for your contact lenses.
Eye doctors usually perform a series of routine tests as part of the eye health exam. Here’s a brief explanation for each one.
These common tests occur at most eye exams. Most people know the “Snellen” Chart as the one with the big “E” on top. This tool determines how well someone is able to see, also referred to as their visual acuity. This tests their ability to read letters without squinting from a distance of 20 feet. Those with normal vision have an acuity of 20/20.
This test determines your ability to distinguish subtle color differences and helps to detect hereditary color vision deficiencies. This test can also detect eye health problems that may affect color vision.
This test measures your stereopsis, or depth perception. The process usually involves viewing images made up of dots or pictures, sometimes through special glasses. This determines how well someone can see in three dimensions. It also helps to detect eye diseases such as amblyopia, strabismus, suppression, and stereopsis.
This test is done to let your doctor determine how well your eyes work together and if there’s any muscle imbalance that may cause one or both eyes to want to not point straight. Muscle testing also helps ensure that all your eye muscles and nerves work well together. Eye muscle tests require very few tools. The doctor asks you to follow an object across six different positions, exposing weakness in muscles.
Pupil testing is usually done with a small bright flash light. The eye care professional shines a penlight over one eye at a time and looks for pupil dilation and contraction.
This test uses a computerized instrument to measure how light focuses through your eye and gives the doctor a preliminary measure of your prescription.
This test also helps the doctor determine your prescription by measuring what lenses it takes to focus light perfectly on the back of your eye.
The pressure inside your eye is very important to measure, because high pressures can be one risk factor for glaucoma, a potentially blinding eye condition. The eye pressure is measured one of several different ways. Doctors will sometimes use a computerized instrument that blows a gentle puff of air in the eye. Pressure can also be measured with various other handheld devices that gently touch the surface of the eye. The doctor may also use an instrument that is attached to the microscope and uses dye in the eye and a blue light.
The refraction test determines the ideal prescription for you. During this test, you are given something to look at (usually the Snellen chart or something similar) and asked to determine your best vision from a series of options. You look through the phoroptor, deciding between two lenses at a time. This is the part of the exam when you can expect to hear “one or two” and “three or four” over and over again. The eye care professional uses your choices to determine which, if any, prescription you need.
Your doctor will use a high-powered microscope called a slit lamp to thoroughly examine the structures on the outside of the eye under magnification. The doctor will also use a strong lens to focus on the structures inside of the eye. During this test, you’ll comfortably place your chin on the chin rest of the slit lamp while the doctor shines a bright light toward the eye.
These tests measure your peripheral vision. Peripheral tests are given by having you look in a fixed forward direction, then introducing images from behind and to the sides of your eyes. This measures how well you can see at the edges of your vision as you focus on a point directly ahead. Visual field testing may also be done with an automated instrument that presents lights or other targets and asks you to click a button when you see them like a video game. Peripheral tests can help discover glaucoma damage as well as neurological problems.
Your doctor will likely need to put drops in your eyes that enlarge the size of the pupil in order to get a wider view into the inside of the eye. It takes about 20 minutes for the drops to work, then the doctor will examine the structures inside the eye with a special headset mounted microscope and with the slit lamp. Pupil dilation will make it a little harder to focus at near distance and will make you more sensitive to bright light, but is a very important test to provide a thorough examination of eye health.
Depending on the examination findings, your doctor may order further testing such as photographs of the inside of your eyes, scanning images of the layers of the retina, or other diagnostic testing as needed.
Contact lenses come in many different shapes, sizes and materials. For people who are interested in wearing contact lenses, the doctor will need to perform extra measurements to be sure that the most appropriate lenses are fit on your eye. This will usually involve actually placing the lens on the eye and evaluating the way the lens sits on the eye surface and moves with a blink.
Once these measurements are found, the other parameters of the contact lens (such as the power) are determined by the refraction test.
It’s important for everyone to have their eyes checked, but there are guidelines about how frequently this needs to happen. Children will need their first exam at six months and again at age three and then before starting school. An eye examination can be a fun experience for children. School aged children should have an eye examination every year because during this formative time the eyes develop quickly and prescriptions can change fast.
Adults who wear contact lenses or who have a family or personal history of eye problems should continue to have eye examinations every year. If there is no history of eye problems, adults between the ages of 20 and 40 should schedule a routine eye examination at least every two years. After age 40 the eyes start to change significantly and there is a greater risk of eye disease. Adults over age 40 should see an eye doctor every year.
Eye examinations with your eye doctor help to maintain healthy eyes and vision as you age. They can uncover many eye ailments such as glaucoma, cataracts, and macular degeneration, and can even detect systemic health problems such as diabetes, high blood pressure, high cholesterol and stroke. Many of these issues can be treated when discovered early.
Updated Aug 25th, 2015
Todd Childs, O.D. has been practicing optometry for the past twelve years. He currently practices at South Valley Optical in Draper, Utah. Dr. Childs earned his Doctor of Optometry at Southern California College of Optometry.