Can Botox Migrate to the Retina if Injected on the Forehead and Cause a Blind Spot?

BOTOX is injected into muscles of facial expression and primarily affects the location it is injected.  A small amount of the agent can spread in the blood stream to cause systemic side effects.  These are minimal for cosmetic treatments.  There effects are primarily associated with injecting BOTOX for medical reasons.  Blindness is not a known side effect of this agent.  So rest assured that your treatment will not cause blindness.  However, there are a variety of reasons that you might experience sudden changes in your vision unrelated to BOTOX.  If you are experiencing a change in your vision you are advised to immediately seek assessment by an ophthalmologist.  If you can't arrange this, go to an emergency room.  They will assess you and have you seen by an ophthalmologist if this is warranted.

No. Botox will not affect the visual part of the retina. It works by preventing nerve communication with muscles that move. There are no moving muscles of the retina. Botox is not a thick liquid that could plug up a blood vessel and interfere with the retina's oxygen supply.

Embolization of Botox via the central retinal artery will not cause retinal injury. However, inadvertent injection of facial fillers into this artery can cause blindness. Rest assured that Botox is safe to inject into the forehead muscles and will not cause distal effects.

Injections of other medications, especially steroids but even fillers, can enter a blood vessel and result in embolization or thrombosis of a vessel.  It this were to occur to the central retinal artery, then it COULD cause blindness.  However, this would be very difficult to accomplish unless you were injecting deep into the orbit, or trying intentionally to inject into another artery that supplies this area.  None of the superficial facial or forehead vessels do this, and so injection of material into these areas is considered safe practice.  

And while these concerns may exist for other materials, the theoretical risk of Botox causing a similar problem is even lower.  Even though Botox has been shown in animal studies to transit the nerve via axoplasmic transport and end up in the cell body in the central nervous system (CNS), the amount of Botox that can make it to the CNS is miniscule and there has never been shown to be any real impact of this phenomenon.  Also, it has never been shown to occur in humans anyway.  

I have never heard of Botox causing blindness. I do not even think this is a theoretical consideration based upon common injection areas. However, with filler, it is a different issue and has been reported and is theoretically possible of filler is inadvertently injected into a retinal blood vessel.