In the [Star Wars][1] movie [A New Hope][2] - we see [Stormtroopers][3] with helmets like the following:

[![enter image description here][4]][4]
[![enter image description here][5]][5]

Then in the Star Wars movie [The Clone Wars][6] - the helmets are shown as T-visors:
[![enter image description here][7]][7]

My question is: **Why did the storm trooper helmets change from the t-visor to the curved eye-sockets?**


  [1]: https://en.wikipedia.org/wiki/Star_Wars
  [2]: https://en.wikipedia.org/wiki/Star_Wars_(film)
  [3]: http://starwars.wikia.com/wiki/Stormtrooper
  [4]: https://i.sstatic.net/dO42K.jpg
  [5]: https://i.sstatic.net/WTU8G.jpg
  [6]: http://www.starwars.com/tv-shows/star-wars-the-clone-wars
  [7]: https://i.sstatic.net/r7xVF.jpg