Visors and sunglasses are typically used to block out the sun. You can usually wear either or both even while wearing a helmet. Sunglasses and visors come in a variety of tints and colors.
The NFL has banned helmet visors unless prescribed by a physician.
They are not allowed in texas. But you can wear a clear visor.
Offensive lineman should not be required to wear visors because many of them have a very large cage. Justin Tuck uses a helmet (I think it's an ION 4D or DNA) that has more bars than I've seen on any other helmet.
The reason dealers wore clear tinted visors was because they were able to see marked cards when looking through them. You may notice that many card discard racks are made from a clear tinted material, it's the same reason as the visor.
Under NFL rules, any player may wear a visor as long as it's untinted. Special approval (and usually a doctor's prescription) is required for tinted visors. NCAA (college) and NFHS (high school) rules go a little further in that they also specify that the visor must be "rigid" (and, as far as I can tell, there's no provision whatsoever made for tinted visors; the visor must be clear and untinted). However, they don't place any restrictions on which positions are allowed to wear them.
I recently stumbled across your clearly defined explanation for players to only wear clear visors on their helmets. I also understand that it is the same in the NFL. Players are not allowed to wear mirrored or tinted visors. Recently about a year or two ago I remember hearing of Miami Dolphin's running back getting fined because he was wearing a "sunburst" design visor. The only exception to these rules that I was able to find, was mentioned in a recent article stating that tinted visors can only be worn with special permission from officials. Now this article referring to the NFL rules.
Majority of NFL players wear oakley visors.
Tinted football visors are allowed in most, if not all high school football leagues. Some leagues or divisions require a signed doctor's note to allow the use of a tinted visor, while others don't.
Astronauts in spacesuits wear helmets with opaque visors, which protect them from the harsh conditions of space. The visors also help regulate temperature and provide oxygen. Additionally, the visors shield their eyes from glare and harmful radiation.
yes they have to wear visors.
yes, yes he does