Is it safe to inject dermal fillers into the brow bone area and supraorbital ridge? Are there arteries that can cause blindness?

It is never 100% safe injecting fillers in this area.  Your experienced injector may use a cannula to reduce but not eliminate the risk of intra-arterial injection of fillers.  However, in this region, there are the supraorbital and supratrochlear arteries that have a very short distance to travel before it is linked to eye arteries.  In fact, some studies have proposed that it takes as little as 0.085 cc of filler material to reach the ophthalmic artery if the suprorbital or supratrochlear artery was injected.  Most of the blindness cases reported around the world is from injection around the eyes and the nose.  However, blindness is possible from injection anywhere on the face.  Furthermore, we have recently published a study has proposed that even a rescue retrobulbar hyaluronidase injection is given, there may not be sufficient penetration into the central retinal artery to dissolve the HA embolism.
Sorry for the long answer, but I want the general public to be aware of certain high risk treatments.  Understanding the risks involved with your expert injector prior to proceeding would be wise.  There are ways to reduce risks but never absolutely safe.  Avoid injectors that do not understand the risks involved.

There is always some risk with any medical procedure including filler treatment. The risk of filler treatment can be reduced by seeing an experienced injector. Slow, low pressure injections using a microcannula are in my opinion the safest in higher risk areas. 

I suppose anything is possible Injecting fillers into brow bone will definitely make them more prominent And supraorbital fillers are performed for multiple reason one is to enhance the eyes and make them look less tired Best of luck Ft Lauderdale

Yes, it is fine to do so with an experienced injector/surgeon who knows the anatomy well. Surgeons actually have 'viewed' the anatomy in their experience rather than just studying diagrams like some injectors. The actual 'effect' you achieve has to be discussed since your goal has to be reasonable