Aging and eye disease Our eyes sensitive to light and be damaged by ROS produced by UV exposure, which is detrimental to vision performance and eye health.
We experience 80% of the sensory information around us through vision. We can say that our perception, cognition, and most daily activities are mediated through vision.
Eyes are exposed to the outside world and are constantly subjected to ultraviolet rays. Light entering the eye reacts with oxygen in our cells, generating a large amount of reactive oxygen species (ROS). These ROS damage our eye cells and the optic nerve, and are thought to be a major cause of eye aging and increase likelihood of developing certain eye diseases.
Presbyopia is the most common symptom of aging eyes, appearing around the age of 40. It is caused by prolonged oxidation of the lens which reduces lens flexibility, making it harder to focus on nearby objects. By age 80, more than half of all Americans either have a cataract (clouding of the lens) or have had cataract surgery according to National Eye Institute.
Only a few antioxidants can reach the eye and protect it from ROS damage.
Your eyes are protected by the blood-retinal barrier (BRB), whose purpose is to prevent toxins and other undesirable things from entering the eye through the circulatory system.
Astaxanthin is one of the rare antioxidants which can both cross the BRB and inhibit ROS damage within our cells, due to its unique molecular structure. Red blood cells carry it into the eye, where it provides both anti-oxidative and anti-inflammatory benefits, slowing the progression of presbyopia and reducing the risk of developing cataracts and age-related macular degeneration (AMD).
Astaxanthin slows down progression of presbyopia.
Presbyopia is the normal, progressive loss of the ability to focus on near objects. Most people begin to notice this condition develop around the age of 40, complaining that text appears blurry when viewed up close. This affects the ability to read books or view smartphones, etc.
When you are young, the lens in your eye is flexible and elastic, and can easily change its shape to focus on close and distant objects. The tiny muscles surrounding the lens are called ciliary muscles, and they contract or relax to adjust the thickness of the lens.
With age, oxidative damage to the lens it stiffer and less flexible. At the same time ciliary muscles weaken with age. As a result, your lens can no longer change shape to focus on close images, and these images appear out of focus. More recently however, people in their 20s and 30s are reporting smartphone-induced premature presbyopia.
In 2009, Kajita Eye Clinic investigated the effect of astaxanthin in 22 elderly participants with presbyopia. After supplementing with 6 mg/day AstaReal® astaxanthin for 4 weeks, participants experienced a subjective improvement in their presbyopia symptoms, and found their vision to be less blurry when viewing objects up close. (Kajita M et al., The effects of a dietary supplement containing astaxanthin on the accommodation function of the eye in middle-aged and older people. Medical Consultation & New Remedies. 2009;46:89-93. (IN JAPANESE))
Astaxanthin benefits for two types of AMD.
Macular degeneration is a progressive disorder affecting the central part of the retina, called the macula. This disorder is due to the gradual loss of photoreceptor cells and is the leading cause of irreversible blindness. AMD appears to be related to light-induced oxidative processes within the eye. While cataracts causes our eye lens to become opaque, in AMD, our ability to sense light is directly affected. Light (particularly blue light) entering the eye interacts with oxygen to produce ROS.
Macular degeneration is diagnosed as either wet (neovascular – producing new blood vessels) or dry (non-neovascular).
“Dry AMD" is a vision disorder caused by the loss of photoreceptor cells and retinal pigment epithelium (RPE) cells, which form a layer under the macular. Inflammation occurring in RPE cells damage both the RPE themselves and the photoreceptor cells.
In “Wet AMD”, new blood vessels are formed just below the retina, and components leaking out from these fragile blood vessels damage the macula. This abnormal growth of blood vessels is due to the impairment of RPE cells which is variously caused by aging.
The dry form of AMD is more common than the wet form, with about 85 to 90 percent of AMD patients diagnosed with dry AMD. However, the wet form of the disease usually leads to a much more serious loss of vision.
Carotenoids seem to play an important role in nature in protecting tissues against UV-light mediated photo-oxidation and are often found in tissues directly exposed to sunlight. Among the many carotenoids available in our diet, the eye selectively accumulates astaxanthin, lutein and zeaxanthin to protect it, and what is remarkable is that astaxanthin protects the whole retina from ROS. (Nakajima Y et.al. (2008) J Pharm Pharmacol. Oct;60(10):1365-74)
Additionally, research has shown that the abnormal formation of new blood vessels in the eye was suppressed in wet AMD by astaxanthin supplementation. The research also showed that astaxanthin’s strong antioxidant capacity, together with its anti-inflammatory properties also suppressed inflammation in wet AMD. (Izumi-Nagai K et.al. (2008). Invest Ophthalmol Vis Sci. Apr;49(4):1679-85.)
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