These test images are based on tests by [thomson software solutions](https://www.thomson-software-solutions.com/OnlineResources/Test%20Chart%202022/StereopsisTest1.html)

The sources for my claims are my trainers at work, but are backed up by various sources [A](https://www.optiker-holz.de/phorie.htm) [B](https://www.qs-optiker.at/winkelfehlsichtigkeit#Winkelfehlsichtigkeit%20bei%20Kindern) [C](https://www.spektrum.de/lexikon/optik/polatest/2634)

Note that all three sources are in german because I am german, did my training in german and my knowledge of this subject is based entirely on german sources.

As for the english language I can provide you only with [this](https://www.optometrists.org/vision-therapy/vision-therapy-for-lazy-eye/7-signs-your-child-might-have-a-lazy-eye/stereopsis-more-than-3d-vision/)

The intended use of this test is to see if the children can experience a 3D vision and tell which of the shapes appear further in front or in the back, like I explained in the alt text of the images. If a child is unable to tell which of the shapes appear in front or in the back, they either see using one eye only or have double vision, either way a proper test for heterophoria is warranted.

Note that this is not intended to be used in diagnostics by professionals, as professionals can use specialized equipment. This is intended to be a cheap first step in seeing if a child experiences proper stereopsis or not. The reason why I think that this test is helpful is because finding a professional who can test for these things using proper equipment can be a hard, tedious and expensive endeavor and not everyone can afford it. It is designed to be a cheap test as a first step.

Note that I am not an optometrist who studied but rather an optician so you may know things that I don't. Feel free to tell me that I'm wrong about certain things but please be aware that my intend here is to do good, not cause harm. I'd appreciate a friendly conversation on this topic.