Sticking to the theme of eye health I wanted to briefly write about cataracts today.  Cataracts are cloudy areas that develop in the lens of the eye, the cloudiness reduces the amount of light transmitted to the retina and this causes poor vision.  In the UK about 1 in 3 people over the age of 65 develop a cataract, which gradually forms over many years.  Initially vision may only be very mildly affected and this may not progress, however, in some individuals the vision will get worse over time. 

Treatment is an option when a cataract becomes bad enough to interfere with normal life e.g. if vision starts to interfere with reading, driving, watching TV etc or stops an individual from doing anything that they would normally do.  Before making a decision about treatment it is recommended to make sure your glasses are giving you maximum benefit.  Treatment involves the removal of the cloudy lens and replacement with an artificial plastic lens (an intraocular implant).

Cataracts seem to occur due to the breakdown and subsequent clumping of proteins in the lens.  Obviously, prevention is always better than cure!  Lifestyle factors that may increase the risk of cataract development include a poor diet low in antioxidant nutrients (found in fruits and vegetables), smoking and prolonged sunlight exposure.  Again, as with AMD, free radicals appear to play a causal role and hence dietary antioxidants may be protective.

I would like to highlight three (1,2,3) very recent research studies.  The first study(1) looked at the association between cataracts and dietary lutein and zeaxanthin, caroteinoids found in spinach, collard greens and kale.  The study involved 1802 women aged 50 to 79 years.  Women with high dietary levels of lutein and zeaxanthin had a 23% lower prevalence of cataract compared to those with low levels.  Women with the highest dietary intakes or highest blood serum levels of lutein and zeaxanthin as compared with those with the lowest were 32% less likely to have cataract.  For more information on these carotenoids and potential supplements please refer to Monday's post which looked at AMD.

The researchers involved in the second study(2) wanted to investigate the relationship between antioxidant nutrient intakes and incidence of age-related cataract over a 10 year period.  The study involved 2464 individuals (aged 49 or over at the start of the study) for 5-10 years.  Eye health was observed using lens photography and dietary intakes of various antioxidants, including zinc, beta carotene, vitamins A, C and E, was assessed.  Individuals with the highest total intake, from diet and supplements, of vitamin C had a 45% reduced risk of cataract.  An above average intake of combined antioxidants -vitamins C and E, beta-carotene, and zinc - was associated with a 49% reduced risk of cataract.  The authors of the study conclude that “Higher intakes of vitamin C or the combined intake of antioxidants had long-term protective associations against development of nuclear cataract in this older population”.

Both of these studies, as in the studies I highlighted in relation to eye health on Monday, re-iterate the importance of a diet rich in vegetables and fruits, which are fabulous sources of antioxidants.  As yet the role for supplementation in the prevention of cataract is unclear (and cannot, of course, substitute diet) but many individuals are taking multivitamin and mineral supplements to help keep their eyes, and bodies, healthy.  Future large supplementation trials are planned and I look forward to seeing the results.

The third study(3) involved around 2000 individuals aged 49 or over (at the start of a 5 year investigatory period).  The researchers found that higher dietary intakes of omega-3 polyunsaturated fatty acids were associated with a significantly reduced risk (42% compared to those with the lowest intakes) of developing cataract over 5 years.   For more information regarding omega 3 fatty acids and eye health please refer to the piece that I posted on Monday which looked at AMD.

(1)Moeller SM et al.  2008.  Associations between age-related nuclear cataract and lutein and zeaxanthin in the diet and serum in the carotenoids in the age related eye disease study, an ancillary study of the women’s health initiative.  Arch Opthalmol.  126:354-364
(2)Tan AG et al.  2008.  Antioxidant intake and the long-term incidence of age-related cataract: the blue mountains eye study.  Am J Clin Nutr.  87:1899-1905
(3)Townend BS et al.  2007.  Dietary macronutrient intake and five year incident cataract: the blue mountains eye study.  Am J Opthalmol.  143:932-939.

Written by Ani Kowal