The problem is that the LED is not bright enough.
LED's have greatly varying maximum brightnesses. A cheap LED from Radio Shack is not likely to be as bright as one could get. Try ordering one from an electronics catalog, or visit a good electronics store.
One of the things that limits the brightness of an LED is the temperature. If it gets hot, I believe the resistance increases. This limits the current. You can try increasing the current, but you fry the LED. One way around this is to cool the LED. If you immerse an LED in a clear dewar flask of liquid nitrogen, it will light up the room. Not as bright as a light bulb, but I would say a good five or ten watts, like a small flashlight.
Of course, feeding liquid nitrogen right next to your eyeball could be uncomfortable.
(In adjusting the brightness of your LED, it is the current that counts, not the voltage. A very small change in voltage will greatly change the current. You want a "regulated current source", the simplest way of doing this is to combine a "large" voltage with a large resistance in series with the LED. That way variations in the resistance of the LED will be small in comparison with the current limiting resistor.
Has anyone tried using a single strand of fiber optic? You can get fiber which is as fine as you care to have it, and with the right optics you can get quite a bit of light to go through.
BTW - see comp.risks today for an article on a recent "mail storm" from Sun. Worse than what we have here today.
Regards,
Mike Crawford Mike_Crawford@QuickMail.Apple.Com