Dry Eye Syndrome (DES)
Sue McGarrigle ND DipION CNHC mBANT
I was recently asked to prepare a lecture for the British Contact Lens Association about nutrition for Keratoconjunctivitis Sicca or Dry Eye Syndrome (DES). It is far more common than I thought and on the rise. In 2011, in England and Wales there were over 6.6 million prescription items for artificial tears, ocular lubricants and astringents dispensed in the community at a cost of over £34.2 million.(1) Prevalence does vary, with the condition more common in older people, (2) millions suffer but increasing dependence on iPads, computers and smartphones plus air conditioning may leave our younger population with an eye problem resulting in gritty, itchy, inflamed eyes, thanks to long hours staring at a screen. ‘When we use such devices, the mind focuses so strongly on the screen we can ‘forget’ to blink’, according to dry eye specialist Dr Christine Purslow Director of the Contact Lens and Anterior Eye Research Unit at Cardiff University, ‘this can affect the eye’s lubrication system and soft contact lens wearers are particularly at risk.
As a nation we are getting older, which means the proportion suffering age-related dry eye is increasing, where the tear film over the surface of the eye deteriorates with age,’ she said. DES can have significant effects on quality of life and common vision-related daily activities, such as driving and reading (3). DES is not usually a serious condition; however severe cases can result in scarring, corneal ulcers and visual impairment (3, 4). Dry eyes can be caused by a deficiency of fluid and disturbances in the tear flow or excess evaporation of the tear film and can be caused by: dry spots on the ocular surface, inflammation of the eye surface, elevated tear film osmolarity with loss of water from the tear film which can activate inflammation and interference of tear film production and stability. (5)
Causes of Dry Eye Syndrome can involve; compensating immune responses leading to inflammation, underlying inflammation e.g. blepharitis, changes in nerve function e.g. lack of tear production, allergic responses e.g. allergic conjunctivitis, changes in hormones e.g. menopause or pregnancy, side effects of medication e.g. anti-histamines, antidepressants, beta blockers and diuretics, environmental conditions, smoking which increases oxidation, ageing, free radical oxidative damage, underlying virus e.g. herpes, pro-inflammatory diet, sugar intake; increasing the risk of dry eye by decreasing the tear break-up time especially when dietary folic acid is deficient.
Consumption of more than 11 teaspoons/day of sucrose is a significant factor linked to reduced tissue potassium levels in dry eye patients. Underlying autoimmune disease; any condition that reduces the production, alters the composition or interferes with the distribution of the tear film may result in dry eyes. DES is often related to other health conditions and may be commonly associated with dryness of other mucous membranes, digestive imbalances or more serious autoimmune diseases, such as rheumatoid arthritis, Sjogrens syndrome or lupus erythematosus which trigger an immune response that slowly destroy the cells responsible for tear production and secretion.
Good nutrition is fundamental to supporting the health of the eye and managing inflammation, oxidation, immune, microcirculation and tissue health: Vitamin C – is concentrated in the tear film to a higher level than that found in the blood. It protects the eye from oxidative stresses including toxins, irritants, allergens and inflammation. Vitamin C is a necessary cofactor for the final phase of production of prostaglandin PGE1 which inhibits ocular surface inflammation, as well as reducing the inflammatory process associated with meibomitis and reduced lacrimal gland aqueous output. Vitamin C is present in high concentrations in the fluid in the aqueous humour. It is thought that vitamin C acts as an ultraviolet filter, helping to protect against cataracts and oxidative damage to the retina and the lens. (6-9)
Rosehips provide a natural rich source of vitamin C and it’s nutritional and biochemical role is enhanced by the synergistic activity of associated food factors such as polyphenols, antioxidants, flavanols and tannins contained in fruits such as pomegranate, plum and blueberry. Singlet oxygen and light induced free radicals are the major causes of eye and CNS related diseases. Carotenoids including Astaxanthin, Lutein and Zeaxanthin protect against oxidative and free radical damage.
Astaxanthin the most powerful carotenoid antioxidant increases the blood flow to the eye, helps focusing ability and reduces eye fatigue. Astaxanthin was found to reduce ocular inflammation in eyes with uveitis by down-regulating pro-inflammatory factors and by inhibiting the NF-kappaB dependent signalling pathway. (10) Dr.Tso of the Wilmer Eye Institute at Johns Hopkins University has clearly demonstrated that astaxanthin is the significant carotenoid when it comes to protecting eyes. He discovered that astaxanthin easily crosses into the tissues of the eye and exerts its effects safely and with more potency than any of the other carotenoids, without adverse reactions and can be effective in preventing or treating a whole host of eye diseases.
In parts of the world where vitamin A deficiency is widespread, severe dry eye syndrome is a leading cause of blindness. Vitamin A is needed for the health of all epithelial tissues, as well as for good night vision. Vitamin A is especially needed to produce the mucin layer of the tears. Beta carotene (pro-vitamin A) has been reported to be helpful in dry eye as well. Vitamin A regulates the proliferation and differentiation of corneal epithelial cells and preserves conjunctival goblet cells. It is required for the synthesis of mucin glycoproteins in the eye. Vitamin A deficiencies negatively affect the lacrimal glands, ocular epithelial cells and conjuctiva. (11)
Vitamin A has been shown to support moist, healthy eyes at a cellular level. Vitamin B6 is important for absorption of magnesium and together they maintain the production of prostaglandin PGE1 for the production of tears. Potassium has been found to be low in DES, linked to dehydration, digestive problems, certain drugs, poor diet, low intake of folic acid, vitamin C and vitamin B6, along with high sugar consumption. Potassium, zinc, calcium, magnesium and sodium are essential and together provide sufficient mineral content in the tear film to promote integrity of the corneal epithelium.
It has been estimated that the ratio of omega-6 to omega-3 fatty acids in the diet of early humans was 1:1, but the ratio in the typical Western diet is now almost 10:1 and can be up to 30:1 due to increased use of vegetable oils over reduced fish consumption. Adequate amounts of nutrient cofactors, magnesium, vitamins A, C, E, B6 and zinc—stabilize both omega-6 and omega-3 fatty acid synthesis. Successful metabolism of omega-6 to the anti-inflammatory PGE1 is secured by omega-3 blockage of arachidonic acid (ARA), and will reduce ocular surface inflammation, as well as the inflammatory process associated with meibomitis and lacrimal gland aqueous output. The Women's Health Study collected dietary information and whether they suffered from dry eye syndrome from 32,470 female health professionals who were aged between 45 and 84 years.
The researchers found that the greater the dietary intake of omega-3 fatty acids the less the risk of DES, after adjustments for age, other demographic factors, postmenopausal hormone therapy, and total fat intake. Tuna fish, rich in DHA, also had a protective effect against DES. (12-15) Combining astaxanthin’s superior antioxidant activity is important to reduce susceptibility to lipid oxidation.
