An article in Science Magazine discusses the role of glucose in both supporting vision and causing vision loss via the retina.
In the back of the eye lies the retina, which enables our vision. The retina contains rods and cones which are types of cells sensitive to light, or photoreceptors. These photoreceptors convert light signals into neural signals in order for the brain to perceive visual information. The rods are highly sensitive to light and are used in peripheral vision and are therefore responsible for monochromatic vision, or scotopic vision. Cones, on the other hand, are responsible for colour vision, also known as photopic vision.
After much curiosity into how these cells acquired their energy, researchers partly delineated the process by studying both the cells of the human eye and mouse retinas. Under normal conditions, glucose from the blood is transferred to the retina via a layer of cells behind the rods and cones called the retinal pigment epithelium (RPE). They found the rods and cones use the glucose but convert what is not needed into lactate and that lactate is used by mitochondria in the retinal pigment epithelium. When deprived of lactate, however, the retinal pigment epithelium uses the glucose from the blood rather than giving it to the retina and the retina begins to die, causing vision loss.
This research also provides a possible reason as to why cones die when rods malfunction. The inability of the rods to convert glucose to lactate induces the retinal pigment epithelium to switch to glucose metabolism, depriving the two photoreceptors of glucose and causing them to die.
This groundbreaking research has recently been reported in Science magazine. This exciting work concerning energy and the retina has begun to reveal the function of glucose in age-related and disease-related vision loss and provides a possible intervention point in the treatment and prevention of these illnesses.
Written by Monica Naatey-Ahumah, BSc
Pennisi, E. (2017 October 17). Your eyes make waste. Without it, you could go blind. Science. Retrieved from http://www.sciencemag.org/news/2017/10/your-eyes-make-waste-without-it-you-could-go-blind.
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and Williams, S.M. (2001). Neuroscience. Available from https://www.ncbi.nlm.nih.gov/books/NBK10850/