Subject: How does eye damage occur when looking at sun during total solar eclipse

In one of the grade ten science classes I teach, during a lab exploring 
human senses one of my students asked why it is so dangerous to look 
directly at the sun during a total solar eclipse.  We were discussing how 
the eye protects itself and increases visibility by the dilating and 
constricting of the pupils.  During the solar eclipse when darkness occurs, 
how can the sun damage the retina?  All my searching yielded only warnings 
against looking directly at the sun at this time because of the possibility 
of even blindness, but none explained how or why this damage occurs.  My 
best guess is that the darkness "tricks" the eye so the pupil dilates, but 
the ring of light at the outer edge must be brighter than we can perceive 
so the exposure acts in a way that is similar to flash burn.  Am I way off? 
My disclaimer is that I'm a chemist not a biologist!

Re: How does eye damage occur when looking at sun during total solar eclipse