The Freiburg Vision Test Battery FrACT₁₀ has learned something new: Any smartphone can be used as a “response box”. Thus, a 4 m viewing distance is easily manageable.

To start, click the button Pair Phone right in the center of FrACT’s main screen, letting a QR code pop up. Scan it with your smartphone, and open the encoded webpage which will look like the figure on the right. Within less than a second, the QR pop-up should go away and near the bottom of FrACT a message will say “Connection to phone response box: success.”

If you have no luck in connecting: reload FrACT, and try pairing again. If there still is no success, contact me bach@uni-freiburg.de.

On the smartphone in the opened webpage you can initiate a test run, e.g. Acuity Letters. FrACT needs to have been calibrated beforehand, and with the phone response box can now entertain the standard 4 m distance without extension cables or Bluetooth. In case you started without calibrating, you can bail out with Reset. To abort during any run, press “Ø”, or press “5” twice. If you reload FrACT, you need to pair anew.

In my testing, the delay from the smartphone to FrACT was 10–300 ms. Since this is not immediate, I added a clicker sound to the response box. If that annoys, turn it off by unchecking Audible button click (near bottom of response page).

Any feedback is highly appreciated; this is totally new, so certainly bugs need to be ironed out. Thanks & enjoy!

PS: How does it work? The transfer between your smartphone and the FrACT device utilises Google’s “Firebase”. It was a non-trivial programming exercise for me 😎, and I had help from various LLMs which were right ≈¾ of the time. To preserve your privacy:

  • Each pairing is based on a random session ID (a unique “UUID”, created on each start/reload of FrACT, something like “0ae387da-…”).
  • No connection to Google is made unless you click Pair Phone.
  • All analysis algorithms in Firebase are off.
  • No personal information about you is transmitted, only the session ID which changes every time you reload FrACT.
  • Every time you send anything with the phone response box, the previous responses are deleted.