When you are alone, a Bluetooth keyboard may help you to respond to the app running on the mobile device more than 2 meters away. You may make the mobile device standing on a table facing you a few meters away, and the app is running in the Autoplay mode which could calculate VA scores. Depending on which eye chart you are using, you may do the following:
- For Snellen, ETDRS and HOTV, you press respective letter keys to respond to each optotype displayed on the screen.
- For Tumbling E and Landolt C, you may press arrow keys to respond to the direction of the opening of the optotype. And in QWERTY keyboard, W is equivalent to the up key, X to the down key, A to the left key and D to the right key, pretty much the same mapping that you had seen in some PC games. Since Landolt C may have 8 opening directions, therefore, Q is for up-left, E for up-right, C for down-right, and Z for down-left.
- For Numbers, you may press the right key when you identify what number displayed, and left key when you can't see clearly.
Using a keyboard is practical if you can do touch typing without watching the keyboard. Wathing the keyboard with an arm-reach distance then staring at the eye chart a few meters aways may impact on the accuracy of the test.
If you are a GP, you may let the patient use the keyboard if the patient is familar with touch typing on a physical QWERTY keyboard.