I've got mine on a timer and it stays on 12 hours a day. But I'm only using a single t8 15 watt bulb that also provides uvb. Though the lighting seems bright in the house, it's really not enough light for many plants. I'm wanting to increase the lighting so I don't have to depend on "low light" plants in the viv. It's only a ten gallon viv and I'm going to go to two t8 15 watt bulbs.

But I'm still planning on a bigger viv at some point and am trying to find out what the intensity level is that actually is a concern for their eyes. They have shady areas where they don't get full light.

However as an exaggerated example..... If I have twenty t8 15watt bulbs over them, lighting this 18inch by 12inch viv, and they leave the shade, are they in immediate danger of blindness? And if so, then what about 10?