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Exploring the medical and scientific background of blood drinking
Investigation and Research Into Sanguinarians
Investigation and Research Into Sanguinarians
Copyright 2005
by Sarah Mediv 
  All Rights reserved 
  E-Mail: s_faolchu@yahoo.com
Ophthlamology
References:

Kolb, Helga.  "Simple Anatomy of the Retina." Webvision. October 8, 2011. Web. <http://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/>

Vorvivk, Linda J "Photophobia." MedlinePlus. June 1, 2011. Web. <http://www.nlm.nih.gov/medlineplus/ency/article/003041.htm>
One of the most common symptoms reported in the sanguinarian syndrome is light sensitivity (also called photophobia). Many sanguins rely on sunglasses heavily during the day and even have sensitivity to florescent indoor lighting. Most commonly, this manifests as headaches after exposure without protection. Are there increases in light collection by the sanguin eye? Other morphic changes? Is it related to a chemical sensitivity? Let us take a look!

FORM AND FUNCTION OF THE EYE

First, how does the eye get light and what mechanisms sense it? Basic biology will teach us the eye has a cornea (clear front part), iris (colored part), lens (part that focuses light), pupil (area in the middle of the iris), retina (that senses light and color) and the sclera (white part that holds it all together). All of these parts come together and the signals produced by the retina are transmitted down the optic nerve to the brain. Interestingly, the right side of vision is monitored on the left side of the brain and visa versa.

Since we are most interested in light sensing and sensitivity, lets look closer at the retina, iris, and pupil. The iris is responsible for expanding and contracting to allow more or less light through the pupil respectively. This light is passed through the lens, which focuses the image onto the retina. the retina itself has two main forms of receptor cells: rods and cones. Rods are responsible for light vision while cones are responsible for color vision. These rods and cones are not completely evenly distributed about the retina, however. The fovea is an area to the temporal side of the optic nerve and is almost explusively cones. The dorsal (top) part of the retina is almost exclusively rods and so has better light sensitivity, but poor color resolution. This is why it is sometimes easier to see things in low light from your periphiral vision then when looking at them directly. In the center of the eye is the optic nerve and it has no rods or cones, a "blind spot" that many optical illusions are based on. 

There are actually many known causes of light sensitivity ranging from some medications to nutritional deficiencies. We know that medications such as doxycycline, ibuprofin and sulfa antibiotics can cause photophobia as well as some herbal therapies such as kava kava and Saint John's Wort. the breakdown of these drugs in the body produce UV sensitive by products that cause photosensitivity (can be in the eyes and the skin as well). We also know some nutritional deficiencies such as vitamin B12 can lead to photosensitivity. As a symptom, photosensitivity can also be part of migraine headaches, meningitis and corneal damage.

PHOTOPHOBIA IN RELATION TO SANGUINARIAN RESEARCH

So, we can see photophobia is likely a part of the syndrome as a whole, but may also be a marker for the underlying cause. When we look at the eye we have to wonder if sanguins have more rod cells then others? Are they distributed differently in the eye? Is it a nutritional deficiency that creates our photophobia? Since photophobia is more likely a syndrome marker, reasearch in other areas may yield more information, though anything that decreases the photophobia and the blood need together would be likely candidates for further investigation.