Common vision tests include color vision tests, refraction tests, visual acuity tests, and visual field tests. All of these tests can be administered during a routine eye exam and some are performed during a regular physical to check for vision changes in a patient, determining if a referral to a vision specialist is necessary. These tests are repeated on a regular basis with the goal of identifying vision problems early so they can be treated before complications develop.
In color vision tests, patients are presented with materials intended to test their color vision. This may be done for a number of reasons, ranging from concerns about inheriting vision defects to worries about changes to the optic nerve that might interfere with color vision. A common example is a set of cards covered in dots of various colors. Numbers and letters are embedded in the dots and will be visible or invisible, depending on someone's color vision capability.
Refraction tests require dilation of the eyes, using eyedrops. The doctor will look into the eyes with a bright light to see how light behaves within the eye and the patient will also be asked to look through a series of lenses to determine if vision correction is needed and see what level of correction is required. After this test, the patient will need to wear protective glasses before going outside, as there is a risk of eye damage caused by bright light when the pupils are dilated.
Visual acuity tests involve seeing how well people can distinguish objects like letters or numbers at various distances. The classic form is the eye chart on the wall, where people are asked to read down the chart and note is taken of the last legible letters for the patient. People who cannot read can be given visual acuity tests involving the identification of shapes and objects on a chart or card, allowing doctors to diagnose vision problems in young children. Other vision tests for acuity include options like the Amsler grid used to check for macular degeneration.
In visual field tests, the goal is to see how much peripheral vision is available to the patient. Doctors can perform this test simply by standing in front of the patient and moving a target like a finger from left to right. The patient reports when the finger is no longer visible and the doctor can take note of the point at which it moved out of the patient's visual field. Changes in peripheral vision identified during vision tests can be a sign of damage to the eyes or surrounding structures.