Does the inverse square law apple? (2 times recc. distance requires 4 times exposure)

The change in the intensity of light follows the inverse square law. The intensity of light decreases by 1/(distance squared) But that doesn’t necessarily equate to the exposure time required by the person using the light. In general the exposure time for light therapy will increase as the intensity of the light decreases but since everyone has different number of receptors in the back of their eyes and the function and secretion from their pineal gland is also likely different, we don’t believe exposure time will follow any mathematical formula. Feel free to give us a call in Vermont at 1-800-786-6850 or email us at hello@verilux.com if you have any other questions or concerns.

How is this different from the $79 model?

This model is designed to be simpler to use with just an adjustable brightness control. The $79 model (I am assuming model VT32) allows you to adjust the color from day light to warm white for added comfort. Feel free to give us a call in Vermont at 1-800-786-6850 if you have any other questions!

Is this rechargeable batteries or 110 volt

This does not have rechargeable batteries. It must be plugged in. The power supply is designed to accept anywhere from 110V to 240V. However, please note that this item does not come with a plug adapter and is only ETL and UL certified in the U.S. & Canada. Feel free to give us a call in Vermont at 1-800-786-6850 or email us at hello@verilux.com if you have any other questions or concerns.

How does this differ from the VT22? (I have that one & like it)

I first ordered the VT22 and returned it for this model. This one has a MUCH better stand that is on the bottom and isn't easily knocked over. It also has 3 levels of brightness. It is almost the same size. I think it is a little taller and a little narrower, but not enough to make a difference. I really love the VT31 over the VT22 and the larger one that I tried out first.