No. That is an old tale designed to discourage the activity. Regarding viagra, I agree that blurry vision should lead a man to discontinue that and related medications, i.e. Cialis & levitra (vardenafil).
No it does not. However if one is on viagra (sildenafil) and experiences blurry vision it would be important to discontinue.
No. While orgasm can result in momentary visual blur, it typically resolves within minutes. Persons using drugs for erectile dysfunction with history of high blood pressure or heart disease should consult their physician since there have been occasional reports of retinal blood vessel blockage related to such drugs.
No relationship. It is an old fiction that masturbation can cause visual blur (and many other problems). Vision is unaffected by this activity.