Can staring at a light bulb for periods of one to two minutes at a time cause permanent eye damage?

Incandescent light bulbs are generally safe to look at. I am wondering why would you stare at an incandescent light bulb for such a long time?

One might think that a 50W incandescent light bulb is more dangerous than a 50 mW laser pen (1000 times less power) but power is only one factor to consider. (Also 50W represents the power consumed by the incandescent light bulb, the emitted power is significantly less than that).

The main factor that makes the laser pen MUCH more dangerous is that the light pen emits a collimated beam, all of which could potentially enter the eye, whereas the light bulb emits in all directions. The amount of power that gets into your eye from the light bulb drops off significantly with the square of the distance from the bulb (if you move twice as far away, the power drops by a factor of 4).

Another factor to consider is the size the the image on your retina. A lightbulb is an "extended source" whereas the laser pen is a "point source". This means that the size of the image spot on the retina will be larger for a lightbulb, and the energy density will be less, reducing the risk of injury.

Also, don't stare at the sun! Staring at the sun is dangerous.