What Happens During an Eye Exam?
A routine (or comprehensive) exam uses a wide range of tests and procedures to evaluate your vision and the health of your eyes. Diagnostic tests are usually performed by a technician. These test results are reviewed by your physician, who will also perform a thorough examination of your eyes. If necessary, your physician may also perform or re-check some of the diagnostic tests.
Tests During Your Eye Exam
The exam may take anywhere from 30 minutes to an hour and will include many or all of the following tests:
Visual Acuity
This test measures the sharpness of your vision using an eye chart projected onto the wall. Both eyes are tested together, as well as the left and right eyes separately. As you read each line out loud, the letters get smaller, until you are no longer able to read the screen.
Visual Field
This will check for blind spots in your side (or peripheral) vision by testing what you can see with your eyes facing forward.
Pupillary Reactions
A technician will observe your pupils’ reactions to light and close objects.
Cover Test
This checks how your eyes work together. As you focus on a small object some distance away, a technician will cover and uncover each eye to observe how much your eyes move. If the uncovered eye must move to focus on the object it may indicate an issue with alignment. The test may be repeated up close.
Alignment
To ensure that the alignment of your eyes is normal, a technician will ask you to follow a target with your eyes in different directions. The technician will observe your eye movements while you do this.
Retinoscopy
If you need of glasses or contacts, a technician may shine a light in your eyes and have you look at a large target while flipping lenses in a machine in front of your eyes and observing the way the light reflects from your eyes.
This yields an approximate idea of your prescription. This is particularly useful for children and patients who are unable to accurately answer questions.
Refraction
To determine your exact prescription, your doctor or technician may fine-tune the prescription manually by asking you to respond to questions such as "Which is better, one or two?" while flipping back and forth between different lenses. If you do not need vision correction you will not be given this test.
Glaucoma
This tests whether the fluid pressure inside your eyes is within normal range. Numbing drops will be placed in your eyes, after which you will be asked to stare directly ahead. A technician will barely touch the front surface of each eye with an instrument called a tonometer or Tonopen, which measures the pressure. This is a quick and painless part of the exam.
Pachymetry
Although not often part of a routine exam, pachymetry may be used on patients who have (or are suspected of having) glaucoma or corneal disorders. This test uses ultrasound to measure corneal thickness.
External Exam
Your doctor will check the visible portion of your eye, looking at things such as the condition of the white of the eyes and the position of your eyelids.
Slit Lamp
The slit lamp is used to examine the health of your eyes. This device gives a highly magnified view of the eye, and allows your doctor to check for eye diseases and disorders by examining your cornea, iris, lens, and anterior chamber.
Retinal Examination
Eye Dilation
To perform a retinal examination, your doctor will dilate your eyes. Pupil dilation enlarges the pupil, allowing your doctor to get a better view of your eye’s internal structures. Dilating drops are placed in the eye, after which it takes 20 to 30 minutes for the eyes to dilate fully—darker eyes often take longer than lighter ones.
These drops will temporarily cause you to be more sensitive to light and will blur your vision. These effects last for several hours, so it is important to bring a pair of sunglasses for the ride home.
