Well, in my opinion, sinus infection cannot leas to optic neuritis. First, you should know that optic neuritis, is well known as retro-bulbar neuritis, and it is a leading cause of vision loss. So in some degree, we can say that it is very dangerous to have optic neuritis. And according to some experts, there are many reasons which can cause it, such as inflammation and damage to the optic nerve. Also, smoking can just increase the risk of getting optic neuritis too. By the way, injury to the optic nerve caused by trauma, as well as indirect trauma from external force can cause damage and subsequent optic neuritis. But there is nothing to do with sinus infection. So you do not have to worry about it.