Myopia is Caused Partially by Long Hours of Study

It is well known that short-sightedness, or myopia, is associated with the intensity and duration of education.[1] But is this cause and effect? A Mendelian randomisation study, beloved of the CLAHRC WM Director, finds strong evidence for a causal explanation.[2] Using this form of analysis there is a statistically strong association between genes that predispose  to long duration of education and myopia. The reverse does not apply; genes associated with myopia are not associated with duration of education. Together, these findings argue against reverse causality.

That said, the effect, although statistically highly significant, is not large. Genes associated with longer education explain only 7% of the variance in the incidence of myopia.  However, they do suggest that something associated with education is causal of myopia, and it is probable that the intensity of book work is also important. The incidence of myopia has risen dramatically in recent years, especially in China, where both the intensity and duration of education have increased over the last generation. Myopia can sometimes lead to blindness. These results are therefore very important.

It seems that children should have a balanced life between looking at books and screens, versus playing in the outdoors. In fact, there are probably other, even stronger, arguments for such a lifestyle prescription.

— Richard Lilford, CLAHRC WM Director

References:

1. Gwiazda J, Deng L, Dias L, et al. Association of Education and Occupation with Myopia in COMET Parents. Optom Vis Sci. 2011; 88(9): 1045-53.
2. Mountjoy E, Davies NM, Plotnikov D, et al. Education and myopia: assessing the direction of causality by mendelian randomisation. BMJ. 2018; 361: k2022.

Antioxidants and Age-Related Macular Degeneration

It is estimated that around 5% of the general population suffer from age-related macular degeneration (AMD),[1] where extracellular material known as drusen accumulate under the retina at the back of the eye and which can eventually lead to blurred or a loss of vision. It has been suggested that antioxidants may help prevent or delay development of AMD in people who do not suffer the condition by protecting the retina against oxidative stress, but it is unclear as to whether this is the case.

A systematic review in the Cochrane Database by Evans and Lawrenson looked at the effectiveness of antioxidant supplements as treatment in people who already had AMD,[2] and found that taking a multivitamin antioxidant vitamin may delay the progression of AMD when compared to a placebo or no treatment (odds ratio 0.72, 95% CI 0.58-0.90). The authors also conducted a systematic review looking at whether there was an association between taking antioxidant vitamins (carotenoids, vitamin C, vitamin E) or minerals (selenium, zinc) and the development of AMD in people without AMD.[3] Five RCTs were included, with a total of 76,756 individuals without AMD. These studies all looked at the use of various supplements against placebo. Generally, the various studies found that there was no effect of supplements on development of AMD, while in some cases there was evidence of an increased risk (see table below).

Comparison	No. of studies	Disease	Risk Ratio (95% Confidence Interval)
Vitamin E vs. placebo	4	AMD	0.97 (0.90-1.06)
		Late-stage AMD	1.22 (0.89-1.67)
Beta-carotene vs. placebo	2	AMD	1.00 (0.88-1.14)
		Late-stage AMD	0.90 (0.65-1.24)
Vitamin C vs. placebo	1	AMD	0.96 (0.79-1.18)
		Late-stage AMD	0.94 (0.61-1.46)
Multivitamin vs. placebo	1	AMD	1.21 (1.02-1.43)
		Late-stage AMD	1.22 (0.88-1.69)

— Peter Chilton, Research Fellow

References:

1. Owen CG, Jarrar Z, Wormald R, Cook DG, Fletcher AE, Rudnicka AR. The estimated prevalence and incidence of late stage age related macular degeneration in the UK. Br J Ophthalmol. 2012; 96(5): 752-6.
2. Evans JR, Lawrenson JG. Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration. Cochrane Database Sys Rev. 2017; 7: CD000254.
3. Evans JR, Lawrenson JG. Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration. Cochrane Database Sys Rev. 2017; 7: CD000253.