The Parks Three-Step Test is used to isolate the paretic muscle in acquired vertical diplopia.
Enter your observations for each of the three tests and the app will suggest which EOM is underacting.
However, I firmly believe you should never fully trust an app to make your clinical decisions! This app explains how the each test is used to determine the final result. Consequently, this application is not only clinically useful but also helps you understand which are the primary EOMs in different fields of gaze.