Lighting is only necesssary in a leopard gecko enclosure to aid the gecko's day and night cycle.  Leopard geckos are primarily crepuscular animals.  They venture out of their homes at dusk and dawn, in the wild.  Having too much lighting in their enclosure can actually damage leopard gecko's eyes.  They do not need UVB or UVA lighting.  A standard low watt light bulb works well in their enclosure.  Should you find your gecko hiding in dark places in their enclosure, your gecko is telling you that there is too much light.