Even if your vision seems fine to you, eye exams can identify potential problems and serious threats, like glaucoma and cataracts, before they get out of hand.
During a comprehensive eye exam, your doctor will exam both the inside and outside of your eyes through a series of tests.
Sharpness and clarity
Visual acuity tests measure the sharpness and clarity of your vision. The doctor will test how well you can see objects, from a distance and up close, by having you identify the smallest line of letters you can read clearly on an eye chart.
How well your eyes work together is measured using the cover test. The doctor will have you stare at a distant object in the room while having you cover each eye alternately. You’ll repeat the test focusing on an object close to you. The doctor uses these tests to assess whether the uncovered eye must move to focus on the target.
To evaluate how well your eyes can follow a moving object and move between two separate objects, your doctor will conduct two tests. The doctor will have you follow the movement of a small light or other target with just your eyes. You’ll then be asked to focus on one object and move your eyes to another to test how well your eyes move between the two objects.
Early on in your examination, the doctor measures the eyes’ refraction using a retinoscope. The doctor shines a beam of light in the eye, then places a series of lenses in front of the eye, and observes the reflection off the retina. The way the light reflects determines if you can see clearly or if you are farsighted, nearsighted or have astigmatism. This test provides the doctor with an estimate of your glasses or contact lense prescription.
The doctor will use an instrument known as a phoropter to develop your final vision prescription. The phoropter is put in front of your eyes, and the doctor shows you a series of lenses. You can identify the ones that make your vision the sharpest.
Two tests can be used to check the fluid pressure of the eyes to see if it is in normal range: the “puff test,” or an applanation tonometer test. During the “puff test” the doctor uses a non-contact tonometer (NCT) to gently push a puff of air onto the eye. Or the doctor may put numbing drops in the eyes and touch the surface of each eye with an applanation tonometer.
These tests can help identify glaucoma, a pressure buildup in the eye, which can damage the optic nerve over time and cause vision loss.
The last step in a comprehensive eye exam is to dilate the pupil. In this test, known as the dilated fundus exam, eye drops are put into the eyes to increase the size of the pupil. The doctor uses a slit lamp and biomicroscope to examine the internal areas of the eye, including the optic nerve, blood vessels, retina, vitreous and macula. Pupils may remain dilated for three to four hours after this test.
It typically takes 30 minutes to an hour to complete a comprehensive eye exam. Your doctor may also offer you optional tests, such as photographing the eye, which may not be covered by your insurance.
After the exam, your doctor will discuss with you any corrective measures you may need and work with you to choose the method that best fits your lifestyle. Whether you need corrective measures or not, the doctor will recommend a date for your next exam.