Self-diagnosis within Arm's Reach

While the minimum predefined distance is 2 meters, you may define an arm's reach distance which should be at least 500 mm (50 cm or 1.64 f). After measuring the distance between your hand/wrist holding a smart phone and your eyes, you input the distance in "Arm's Reach Distance" in Settings, then this distance will appear in the Predefined Distances.

Remarks:

To identify nearsightedness symptoms, the test distance should be at least 2-meter which is longer than arm's reach. Since generally an arm's reach distance is much shoter than 2-meter,  this testing mode is good only for casual self-diagnosis for example when you are on a train, and the test result is inaccurate and unreliable. It may be easier to use Self-diagnosis with a Mirror.