A visual acuity test is a medical examination that assesses the sharpness of a person’s vision. The test is commonly performed as part of a routine eye examination, as well as in the diagnosis and management of various eye conditions.
During a visual acuity test, the patient is typically asked to stand or sit a specific distance away from an eye chart, which displays rows of letters, numbers, or symbols of decreasing size. The patient is then asked to read out loud or identify the symbols on the chart from top to bottom. The smallest line of symbols that the patient can accurately identify determines their visual acuity.
The results of a visual acuity test are typically reported as a fraction, with the top number indicating the distance at which the patient was tested (usually 20 feet in the United States) and the bottom number indicating the smallest line of symbols that the patient could accurately identify. For example, if the patient can accurately identify the symbols on the 20/30 line, this means that they can read at 20 feet what a person with normal vision can read at 30 feet.
Visual acuity tests can be performed using various types of charts and symbols, depending on the patient’s age, ability, and other factors. In addition to standard charts, some tests may use pictures or other symbols to assess visual acuity in young children or individuals with difficulty reading letters or numbers.
Visual acuity tests are important for detecting and monitoring a range of eye conditions, including refractive errors (such as nearsightedness, farsightedness, and astigmatism), amblyopia (lazy eye), cataracts, macular degeneration, and glaucoma. By accurately measuring a patient’s visual acuity, healthcare providers can make informed decisions about the need for corrective lenses, medications, or other interventions to manage and treat these conditions.