* Children who develop myopia by the age of 10 have a diet that is lower in energy intake, protein, fat, vitamins B1, B2 and C, phosphorus, iron and cholesterol (Optom Vis Sci, 1996; 73: 638-43).

* A further hypothesis linking diet to the development of myopia comes from ophthalmologist William Jory (bmj.com/ cgi/eletters/324/7347/1195#22422). He bases his work on his own studies done in North West British Columbia on teenagers, contrasting both their high prevalence of myopia and greater height with their better-sighted, stockier parents. He suggests this increase in long-bone measurement happened along with an increase in the axial length of the eye, causing myopia, and both were due to a sudden change of diet from high-protein meat and fish to a high-carbohydrate Western-style diet in a single generation. It was noteworthy, he says, that the further these tribes lived from a Western-style fast-food outlet, the lower the incidence of myopia.

* Wearing rigid, gas-permeable contact lenses may slow the development of myopia. Several studies have indicated that children given this type of contact lens benefit from a slowing of the expected progression of shortsightedness. A major trial is taking place in Ohio to ascertain how effective this is. The theory is that children benefit because wearing these lenses flattens the cornea. The trial (called the CLAMP study, Ohio State University College of Optometry) is due to finish this year and is expected to be published soon after.

* There are claims that eye exercises - and there are a number of types - can improve shortsightedness, but there are no clinical trials showing any clear benefit. Perhaps the most famous of these is the Bates method, developed in the 1920s by American oculist William Bates and brought to the public by writer Aldous Huxley in his much-reprinted 1942 book on the Bates method, The Art of Seeing (Flamingo Modern Classics, 1994).

* There is a growing interest in the impact of nutritional and lifestyle factors on eye health in general. The US Age-Related Eye Disease Study (AREDS) is an important ongoing study that may teach us a lot about ways of preventing and treating the progression of eyesight problems in older people. So far, significant benefits have been seen in the field of age-related macular degeneration (AMD), which leads to a progressive loss of sight. Nutrients included the antioxidant vitamins E, C and beta-carotene, and zinc with copper. In the AMD trial groups, those at high risk of developing advanced AMD lowered their risk by about 25 per cent when treated with megadoses of antioxidants combined with minerals (Can J Ophthalmol, 2003; 38: 27-32; Arch Ophthalmol, 2001; 119: 1417-36; Insight, 2002; 27: 5-7).