NIH Toolbox Visual Acuity Test TASK

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This test directly measures participants’ visual acuity or distance vision. The participant is seated 12.5 feet away from a computer monitor at eye level, and letters (called “optotypes”) are displayed one at a time on the screen for the participant to identify, using both eyes at the same time, with the participant wearing his/her normal corrective lenses for distance vision (glasses or contact lenses), if worn. As the participant successfully identifies optotypes of a given size, smaller ones appear on the screen, until the computer program ascertains the smallest-size optotype the participant can successfully see. Conversely, the program displays larger optotypes if the participant cannot see the size that is first displayed, until a size that he/she can accurately see is found. For participants ages 3-7, only the letters H, O, T and V are used, and children may point to a laminated card showing the letters if they cannot verbalize or recall the letter names. For participants ages 8 and above, the entire set of optotypes is used, following a common protocol used in professional vision testing. This is the standard binocular visual acuity measure scored in LogMAR units.

Definition contributed by Anonymous
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