http://jcem.endojournals.org/cgi/con...ull/88/11/5315

There are two types of blindness. This study was done with totally blind patients.

Other forms of blindness the patients see light and would not
be good subjects for this test.

There are melatonin receptors in the normal retina. It is thought that these receptors are connected to the circadian expression of melatonin for night sleep.

Another:
http://www.lef.org/magazine/mag96/oct96_abstracts.html

http://www3.interscience.wiley.com/j...TRY=1&SRETRY=0

http://www.ncbi.nlm.nih.gov/pubmed/9...?dopt=Abstract

Effects of drugs and nutrients on melatonin:
http://www.spineuniverse.com/display...ticle1105.html

http://www.umm.edu/altmed/articles/melatonin-000315.htm

If you still use Coumadin, taking melatonin is not advised.
You could still encourage endogenous production with
methylcobalamin.

A reading in the 600's is just above borderline.
You probably could benefit from 1mg daily of oral methylcobalamin which is not expensive.
example:
http://www.iherb.com/ProductDetails.aspx?pid=129&at=0
local stores typically do not carry this. Most of us buy it online.

In some other countries 500 is the cut off for treatment.

Also with the new information coming out about Vit D and the new data surrounding it...you should get a Vit D test done to see if you are low. Many people on the net on forums like this with neuro issues and/or chronic pain/fibro and other problems benefit from fixing blood levels to the normal range.

http://www.vitamindcouncil.org/
from depression, cancer, osteoporosis, etc are finding improvements with this new information.

B12 and Vit D are the two most obvious new issues involving hidden deficiencies.

There are others however, which you can explore later.

I found methyl B12 very helpful during my menopause. I had terrible sleeping problems then...that was my main complaint.
I used and still use 1mg daily. And my levels were 849 on testing before using it.