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Astaxanthin for
Eye Health

Printable Version

The Problem

Asthenopia otherwise called eye fatigue occurs on a daily cycle, in that the visual performance generally decreases naturally from morning until night.

The Symptoms

The symptoms of asthenopia include sensitivity to glare, headaches, sore eyes, and blurred vision. Standardized questionnaires that assessed subjective eye fatigue find that symptoms are in most cases mild, but get progressively worse if the causes are not rectified.

The Causes

This phenomenon known as asthenopia prompted a large number of occupational safety studies. For example, epidemiological studies over the last decade revealed significant factors that contribute to eye fatigue. These studies, sometimes involving up to 6,000 sufferers identified the following causes: insufficient lighting, poor ergonomics and uncorrected vision. Despite the new information, follow-up studies later showed that implemented improvements were only effective in 50% of sufferers. The possible explanation for this observation could be that other factors remained undiscovered, poor implementation of improvements, or visual work had become even more visually demanding. It is likely to be a combination of these factors so that current solutions are insufficient to reduce asthenopia.

More recently, the advances of information technology, software and electronics have led to the widespread use of screen based equipment or visual display terminals (VDT) especially at work or leisure. VDT’s are important because it forms the essential interface between an operator and computer to perform specific tasks. The problem acknowledged by the ophthalmic community is that habitual use of VDTs often leads to higher visual fatigue complaints.

The Solution

Beside removal of the cause of eye fatigue, which is often not practical, there has to date been little progress toward relief of this growing problem. In answer to this challenge Fuji Chemical Industry of Japan has focused on the research of astaxanthin for the relief and prevention of eye fatigue. To date, Fuji has sponsored 9 human clinical studies performed at 6 different research institutions.

The Science

Reducing Asthenopia
A couple of randomized double blind placebo controlled pilot studies demonstrated the positive effects of astaxanthin supplementation on visual function. For example, a study by Nagaki et al., (2002), demonstrated that subjects (n=13) who received 5 mg astaxanthin per day for one month showed a 54% reduction of eye fatigue complaints. In a sports vision study led by Sawaki et al., they demonstrated that depth perception and critical flicker fusion had improved by 46% and 5% respectively on a daily dose of 6 mg (n=9). The effect of astaxanthin on visual performance prompted a number of other clinical studies to evaluate the optimum dose and identify the mechanism of action.

A study by Nakamura (2004), demonstrated significant improvements in reducing asthenopia and positive accommodation for the 4 mg (p<0.05) and 12 mg (p<0.01) groups. However, it was not until Nitta et al., (2005), who established the optimum daily dose at 6 mg (n=10) for a period of 4 weeks by comparing eye fatigue using a visual analogue scale (VAS) based questionnaire and accommodation values. Overall, the 6 mg group improved significantly better at week 2 and 4 of the test period. Furthermore, questionnaire results obtained by Shiratori et al., (2005) and Nagaki et al., (2006), also confirmed the previous findings that astaxanthin supplementation at 6 mg for 4 weeks improved symptoms associated with tiredness, soreness, dryness and blurry vision. Another study by Takahashi & Kajita (2005), also demonstrated that astaxanthin attenuates induced-eye fatigue, as opposed to treating eye fatigue, which suggests prevention rather than treatment. Astaxanthin treated groups (asthenopia negative) were able to recover quicker than the control group after heavy visual stimulus. Later, Iwasaki & Tawara (2006) also confirmed the same tendencies of subjective eye fatigue complaints in a randomized double-blind placebo controlled double-crossover study.

Mechanism of Action: Improved Accommodation, Increased Retinal Blood-flow and Improved Ciliary Body Function
Accommodation measures the lens refractive property and it corresponds to the ciliary body function. This small ocular muscle controls the lens thickness in order to focus the light on the retina. In heavy visual workloads, the eye is focused on a fixed object distance for extended periods that will cause muscle spasms or develop fatigue detectable by accommodation tests. These tests are interrelated and include the following: accommodation amplitude; accommodation reaction (positive or negative) and high frequency component (HFC). Each clinical study used a combination of accommodation tests to indicate the amount of fatigue present. For example, increased accommodation amplitude in all treated subjects indicated improved reaction on near and far objects (Nagaki et al., 2002, 2006; Nakamura et al., 2004). reveal the higher rate of accommodation reactions measured in astaxanthin treated groups. These indicate the speed at which the ciliary body reacted to the direction change of focus (negative accommodation means from a near object at 35 centimeters to distant object at 5 meters or vice versa); (Nitta et al., 2005; Shiratori et al., 2005; Nakamura et al., 2005; Iwasaki & Tawara, 2006). The effects of astaxanthin are significant from 2 weeks.

Another technique called HFC directly measured the microfluctuations in the lens during the accommodation response and typical values exist between 50 and 60 for normal eyes. Asthenopia sufferers (values greater than 60) experienced faster rates of recovery in that their HFC results decrease towards normal values in less time compared to control groups (Takahashi & Kajita, 2005).

Another randomized placebo controlled study by Nagaki et al., (2005) detected the increase of retinal blood flow in the astaxanthin treated group that received 6 mg for 4 weeks (n=14, p<0.01). Even though the precise reason for accommodation improvement seen with astaxanthin is not yet clear, the author postulated that based on the rheological improvement measured in the retinal capillary vessels, most likely means more blood also reaches the ciliary body and provides more nourishment to the ciliary muscles. Furthermore, the rheological improvement agreed with Nagaki et al., (2005) who studied ten healthy subjects treated with 6 mg astaxanthin for ten days. The blood exhibited significantly higher flow rates (ex-vivo) compared to the control group (p<0.05) utilizing the micro-array channel flow analyzer (MC-FAN).

Lastly, a top Japanese ophthalmology research collaboration between Hokkaido, Yokohama and Tokyo concluded anti-inflammatory properties of astaxanthin in endotoxin-induced uveitis (EIU or eye inflammation) both in vivo and in vitro models. Ohgami et al., (2003) observed in a dose dependant fashion that astaxanthin doses of 1, 10 or 100mg/kg dose in rats had the same anti-inflammatory action as 10 mg/kg prednisolone (n=8, p<0.01). Inflammation markers such as nitric oxide synthase (NOS), prostaglandin E2 (PGE2) and tumor necrosis factor (TNF)-a were all significantly reduced. In human terms, 4 mg astaxanthin per day may deliver the same benefits as 4 mg prednisolone without the side effects of intraocular pressure build-up. Other reduced biomarkers were cellular infiltration and protein build up in the aqueous humor.

In another study, Suzuki et al., (2006) confirmed the same effects while they carefully studied the anti-inflammatory effect of astaxanthin in the iris-ciliary body of rat eyes. This was also the first study to prove that astaxanthin suppressed NF-kB activation by free radicals in the EIU rat model (Figure 8). The result is a lower pro-inflammatory response that would otherwise perpetuate local sites of inflammation that may also help explain why astaxanthin worked to alleviate eye fatigue in numerous clinical trials.

References

  1. Iwasaki & Tawara, (2006). Effects of Astaxanthin on Eyestrain Induced by Accommodative Dysfunction. Journal of Eye (Atarashii Ganka) (6):829-834.

  2. Suzuki et al., (2006). Suppressive effects of astaxanthin against rat endotoxin-induced uveitis by inhibiting the NF-kB signaling pathway. Exp. Eye Res., 82:275-281.

  3. Nagaki et al., (2006). The supplementation effect of astaxanthin on accommodation and asthenopia. J. Clin. Therap. Med., 22(1):41-54.

  4. Miyawaki et al., (2005). Effects of astaxanthin on human blood rheology. J. Clin. Therap. Med., 21(4):421-429.

  5. Nitta et al. (2005). Effects of astaxanthin on accommodation and asthenopia – Dose finding study in healthy volunteers. J. Clin. Therap. Med., 21(6):637-650.

  6. Shiratori et al. (2005). Effect of astaxanthin on accommodation and asthenopia – Efficacy identification study in healthy volunteers. J. Clin. Therap. Med., 21(5):543-556.

  7. Takahashi & Kajita (2005). Effects of astaxanthin on accommodative recovery. J. Clin. Therap. Med., 21(4):431-436.

  8. Nagaki et al. (2005). The effects of astaxanthin on retinal capillary blood flow in normal volunteers. J. Clin. Therap. Med., 21(5):537-542.

  9. Nakamura et al. (2004). Changes in Visual Function Following Peroral Astaxanthin. Japan J. Clin. Opthal., 58(6):1051-1054.

  10. Ohgami et al., (2003). Effects of astaxanthin on lipopolysaccharide-induced inflammation in vitro and in vivo. Invest. Ophthal. Vis. Sci., 44(6):2694-2701.

  11. Nagaki Y., et al., (2002). Effects of astaxanthin on accommodation, critical flicker fusions, and pattern evoked potential in visual display terminal workers. J. Trad. Med., 19(5):170-173.

  12. Sawaki, K. et al. (2002) Sports performance benefits from taking natural astaxanthin characterized by visual activity and muscle fatigue improvements in humans. J. Clin. Ther. Med., 18(9):73-88.

The Outlook

Although some might argue that asthenopia is non-life threatening or not disabling compared to a condition such as age-related macular degeneration, the phenomenon contributes to the functional discomfort that greatly affects the quality and performance at work and leisure. Eye fatigue, a problem which for the most part is still untreated welcomes a complementary alternative such as astaxanthin based on the current clinical evidence showing improved accommodation, reduced inflammation and increased blood flow.

For a complete study reference list or more information, contact Fuji Health Science, Inc.

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