Increase in myopia

A recent study in the Archives of Ophthalmology confirms what we’ve all probably suspected, which is that the prevalence of near sightedness or myopia is on the rise.  The study headed by Susan Vitale of the National Eye Institute examined National Health and Nutrition Examination (NHANES) population data from 1971-1972 and compared it to the NHANES data from 1999-2004.  This is the same data set that we examined to compare the increase of obesity and food supply to conclude that the obesity epidemic is due to a push effect of too much food (see here).  The prevalence of  myopia increased from 25% to 41.6%.  The greatest increase in myopia was for African Americans, who doubled their prevalence.  Whites increased by about 30%.

The conventional wisdom is that the increase in near activities such as reading, surfing the web, texting and watching TV are the cause for this dramatic rise in myopia.  However, a group in Australia have been arguing that it is the lack of outdoor activities during childhood that may be the most to blame.  Papers in Opthalmology in 2008 for Australian children (age 6 and 12) and in 2010 in the British Journal of Opthalmology for Singaporean children (ages 11-20)  show that the number of hours spent outdoors was significantly correlated with less myopia.  To control for genetic factors, they also just looked at children of Chinese descent in Australia and Singapore.  Both studies found a protective role for outdoor activities and a further protective role for outdoor sports such as soccer, softball and baseball for the older children but only for 6 year old  boys.  They also found that it wasn’t a threshold effect – the more you play outside the less likely to have myopia. Interestingly, playing sports indoors did not have a protective effect so some combination of being outside and playing sports (and perhaps visually oriented sports) seems to help. The effect is also independent of the amount of time spent reading.  It would be interesting to repeat this study in the northern hemisphere where it is cold and dark for half the year to see if that plays a role.

I think there may also be a business opportunity to develop displays that put the point of focus at infinity (as well as mimicking being outside).  Although, it is still not known why being outdoors helps (it could be exposure to higher light intensities including UV light for example), I still believe that focusing at infinity rather than at 18 inches must help even if it is only to alleviate eye strain.  The display would essentially be a simplified 3D viewer where the experience of editing a document would change from staring at letters directly in front of you to looking at a supersized billboard sitting on a mountain top in the distance.

Addendum 2010-2-10:  You would also need to apply ray tracing software to the image to mimic the effect of a converging lens to put the image at infinity, in effect blurring the image unless you focused at infinity.


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