Previous Versions can be found here.
Astigmatism is a decently strong card with the ability to kill the monster in front of it when every time your turn begins, effectively making that slot useless to most of the opponent's cards until Astigmatism is killed. Also, if it couldn't kill a monster, it will add a Loox to your hand.
Unfortunately, it's not the most survivable monster being 3/6 for 6G with no other effect, so it's beneficial to have a Taunt monster to protect this.
While facing against one, it can be used to activate the Dust effect of your monsters, namely Mettaton NEO.