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Questions and Answers
What does the top number in a visual acuity test fraction represent?
What does the top number in a visual acuity test fraction represent?
What does a visual acuity of '20/40' indicate?
What does a visual acuity of '20/40' indicate?
What is 'optical infinity' in the context of visual acuity testing?
What is 'optical infinity' in the context of visual acuity testing?
Which factor does NOT affect visual acuity?
Which factor does NOT affect visual acuity?
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How does presbyopia impact visual acuity?
How does presbyopia impact visual acuity?
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What happens in amblyopia that affects visual acuity?
What happens in amblyopia that affects visual acuity?
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Study Notes
Visual acuity is a measure of the spatial resolution of the visual processing system. It is typically tested by requiring a person to identify optotypes, or stylized letters or symbols, on a printed chart from a set viewing distance. Optotypes are represented as black symbols against a white background, and the distance between the person's eyes and the testing chart is set so as to approximate "optical infinity" or at a defined reading distance (known as near acuity).
The results of a visual acuity test are usually written as a fraction. The top number represents the distance between the person and the chart, typically 20 feet. The bottom number is the line on the chart that was correctly read. For example, a result of "20/20" indicates that the person can read the line that those with normal vision can read, while a result of "20/40" means they can see at 20 feet what those with normal vision can see from 40 feet away.
Visual acuity can be affected by various factors, such as refractive error (nearsightedness, farsightedness, or astigmatism), illumination, contrast, and the location of the retina being stimulated. Additionally, age-related changes, such as presbyopia, can impact visual acuity, as can conditions affecting the retina (e.g., retinal detachment or macular degeneration) or the brain (e.g., amblyopia).
Visual acuity testing is an important part of a comprehensive eye exam and is used to screen for visual impairments, aid in the diagnosis of refractory eye disease, evaluate acute changes in vision, and re-evaluate vision after corrective procedures or interventions. It is typically performed using a Snellen chart, although other charts, such as the Tumbling E chart, Landolt C chart, Allen chart, or LogMAR chart, may also be used.
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Description
Test your knowledge on visual acuity, optotypes, and factors affecting vision in this quiz. Learn about how visual acuity is measured, the significance of results, and the various charts used in visual acuity testing.
