In the convergence apparatus, the idea of Bangerter has been used – so-called “snail”.
The AK-1 Convergence Trainer consists of a base on which two guide bars are placed in the form of two parallel metal rods. The guide allows for free movement between the brackets of the mechanism driving the test disk (Archimedes’ spiral). In the lower part of the mechanism there is a handle for moving the disc. On the front support there is a chin rest for comfortable observation of the moving test disc.
Thanks to the distance control and rotating “snail disc”, patient gets a very strong stimulus for the convergence (also in case of very low or underdeveloped fusion). The use of a rotating spiral makes it easy to focus attention on its center point.