Check your eyes is an eye exam that checks how well you see the details of a letter or symbol from a specific distance.

Check your eyes refers to your ability to discern the shapessizecolours and details of the things you see.
There are several different types of visual checks most of which are very simple. Depending on the type of test and where it’s conducted the test can check your ability of the folowing things:
Acuity vision
Colour vision
Contrast vision
Focus vision

No risks are associated with Check your eyes app and you don’t need any special preparation.
But you have to know it will not be alternative to ophthalmologist or to your eyes doctor.