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Calibrate to your vision

Different people have different levels of vision ability. To make a calibrated assessment, it is first necessary to determine the vision ability of the assessor, by reading some test-chart letters. To do this now, please follow the instructions below.

  1. On your phone, set your screen brightness to maximum.
  2. Unroll your tape measure to the 10 cm mark, and use the button to lock it off. Place it next to the image shown below.
  3. Use the — and + buttons below to alter the size of the image of a tape measure, until the 3 and the 7 cm marks line up with the real tape measure. This makes sure that test-chart letters can be displayed on your screen at exactly the right size.
tape measure
  1. Roll the tape measure out along the floor, so that the metal end is touching a wall. Press the button to lock the tape measure off.
  2. Prop this phone against the wall at eye-level. This is most easily achieved by asking an assistant to hold the phone against the wall at the right height.
  3. If you wear glasses for distance (e.g. driving), then wear them for this test.
  4. Walk backwards and forwards until you find the furthest distance away from the phone where you can read the letters below ‘quickly and with certainty’.
  1. Note the position of your big toe on the tape measure (in cm).
  2. Enter this number in the box below. It will be stored on this device for future reuse, and is specific to your eyesight.

Enter your Calibration Distance (cm) in the box below:



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