author=Neil_E says:
'Stephen; I would concur with Pete, its to enhance the chances of getting very small parts in the right place when normal eyesight fails.
I guess they would accentuate flaws given the magnification but it up to the modeler to correct these or be relaxed enough to ignore them if they are not crucial and not overly visible to the naked eye...'
Very good Neil_E & PeteLH. Optivisors enlarge the image so we can get better fit to the pieces were putting together. Flaws can be minimized. Aim small - miss small. (She was a great gal by the way)
'...I found optivisors to feel a bit odd and unwieldy to wear but that is my my personal preference only.
I am concerned about their overall affect on eyes given they are not prescription lenses.'
(The visiting prof. whispers)Pssssssst Neil, your supposed to wear your prescription lenses with the optivisor. That way your RX is magnified and there's even less chance for your eyes to be strained . 
Next we move on to The use of Accelerants: There are several types. The most common are:
1. Over the counter types. These are composed of Triethanolamine or other similar amines. They usually carry the label 'Suspcted Carcinogen' Just a little tip. If there has been cancer in your family or you smoke Don't use these over the counter types. Its too risky. My youngest son (13 today- will be pronounced 'cancer free' in June this year, after 7 long years of struggle.) I have done some serious studies into this, I have used the accelerant in the past and what I learned is I'll never use it again.
2. When used with Cyanoacrylate estre type glues, Baking Soda / Micro Balloons are converted to a level of a minute toxic gas for about .0154 of a second in a well ventilated work area. I have used such 'welds' for nearly 25 years and I have yet to have a joint fail. Within 5 minutes is hard as nails.
Fumes need to be avoided and NEVER directly inhale from an open container such as Testors acrylic paint remover or thinner. Roughly 2% of the population are allergic to its fumes (I am one) It will close your eyes and cause possible respiration concerns. Its effects could take about 16-20 hours to pass through your system.
Caution is the Name of The Game Folks. When ever you try a new chemical try to get a copy of the MSDS (Material Safety Data Sheet) and follow all directions. I use simple paper masks when I feel the need. For further reading I heartily suggest, Finescale Modeler Finishing School Lesson #6 for your homework. Ask your self do you know the hazards?
Pop Quiz: What makes a substance Toxic?