Optics Course : Astigmatic fan/Dial : principle behind and how to use.

This video is available with better sound quality at https://youtu.be/DvfjAY7i2Fw
Astigmatic fan /Dial is of help for the subjective diagnosis of astigmatism as well as for the description of the correct glasses. This video explains the idea behind it use and how to practically make us of this simple technique at hand.
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Видео Optics Course : Astigmatic fan/Dial : principle behind and how to use. канала Adel Abdelshafik