Neira | ARTICLE
the regular time of day, which is the case for most patients with NLP (Berson, 2002). Over time their circadian rhythms can get disarranged with regular daytime hours causing tremendous fatigue and exhaustion throughout the day. Therefore, many people who have NLP suffer from a circadian rhythm disorder called Non-24-Hour Sleep Wake Disorder (Non-24). Of all blind patients with NLP, 70% suffer from Non-24 (Vanda Pharmaceuticals Inc., 2015). Many blind people with Non-24 are not able to keep their jobs as a result of this disorder because their exhaustion is so extreme that they can fall asleep at unexpected times without control. According to the National Sleep Foundation (2015), there are three treatments for Non-24: phototherapy, the intake of a drug called Tasimelteon, and the treatment of melatonin. Specifically for blind people with NLP, phototherapy is the least useful because the patient does not detect the light used in the treatment at all since the light used is purposely weak in order to not damage the eyes of people who can still see. Tasimelteon is effective in helping to regulate the circadian rhythm; however, there are many side effects that can be harmful for older blind patients. The use of melatonin is thus the most reliable source of treatment for patients with NLP, but the patient would have to continuously take melatonin for the rest of their lives, a feat that may become financially difficult for some people. Thus the introduction of a new treatment must be implemented, one that is both economically friendly and effective. We are then left with a treatment that must trigger an internal response without the use of drugs. The result? Phototherapy again. Only this time, the phototherapy will not depend on weak white light, but a powerful blue light. From the visible light spectrum, blue light has the shortest wavelength and most energy. The problem with regular phototherapy for people with NLP is that the treatment uses relatively low-energy light to prevent any damage to a sensitive eye); however, most people with NLP do not have sensitive eyes and thus cannot register this weak light (Vandewalle et al., 2013). For this reason, a powerful blue light will be used in our experiment. How can the exposure of blue light lead to the regulation of the circadian rhythm? The answer lies within our eyes. Initially it was believed that humans were able to perceive light through two photoreceptors in the eye called rods and cones. Rods are cells that respond to low-light vision and transmit black and white shapes to the brain. Cones, on 28 | Issue 1 | Volume 7 | Fall 2017
the other hand, are cells in the eyes that are able to register color. It was thought that light was only perceived through these two photoreceptors until Clyde E. Keeler accidentally bred mice that were born with no rods and cones (Keeler, 1924). These mice were completely blind, yet when light was shone into their eyes, their bodies responded to the stimuli and their pupils dilated. The study showed implications that there is a nonvisual way in which we perceive light. Yet how was this possible if none of the mice were born with rods and cones? Keeler wondered over this enigma for years but could not figure out the reasoning behind this phenomenon. Unfortunately, his work was left untouched for decades and the mystery of the perception of light was left unsolved for many decades to come until Russell G. Foster dug up Keeler’s work in 1991. After extensive experiments, Foster’s work showed a correlation between the circadian rhythm of blind mice and the exposure of light, indicating that the circadian rhythm is still able to regulate itself without the presence of rods and cones (Foster et al., 1991). In his experiment, Foster realized the mice that were exposed to light had slightly different sleep cycles than those who were not exposed to light. Therefore, there was an unknown cell somewhere within the eye that was sensing the presence of light (Vandewalle et al., 2013; Owens et al., 2012); however, it would take yet another couple of years before these mysterious cells were found. After far-reaching research, the discovery of these mysterious cells was finally made. These special cells are called intrinsically photosensitive retinal ganglion cells (ipRGCs) and transmit light signals to the brain (Weng et al., 2009; Owens et al., 2012). To this day, there is still limited research on how ipRGCs function in human eyes and even less on how the stimulation of these ipRGCs can be used to help regulate the circadian rhythms of blind patients. The predicted general outlook of the role of ipRGCs is that these cells send an electrical message to the suprachiasmatic nuclei (SCN, located in the hypothalamus within the brain) when light comes in contact with the eye. Once in the hypothalamus, the message is transferred to the pineal gland where melatonin is either released or suppressed depending on the initial message (Schmoll et al., 2010); thus, ipRGCs may very well have a direct correlation with the regulation of sleep (Owens et al. 2012, Weng et al., 2009; Flynn-Evans et al., 2014). However, Owens’ study showed that there is The Undergraduate Journal of Neuroscience