The glass lense has very little to do with it. The real advatage is they are ellipsoidal projectors. Rather than reflecting the light, the light is aimed (projected) ahead, giving you a 30% increase in lowbeam range.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>