Environment (outdoor, reading, diet, etc.)
Lisa A. Jones-Jordan, Loraine T. Sinnott, Susan A. Cotter, Robert N. Kleinstein, Ruth E. Manny, Donald O. Mutti, J. Daniel Twelker and Karla Zadnik. (2012) Time outdoors, visual activity, and myopia progression in juvenile-onset myopes. (ABSTRACT) Invest. Ophthalmol. Vis. Sci. September 13, 2012, doi: 10.1167/iovs.11-8336

MyopiaPrevention.org comment: Unlike prior studies, this one did not find any benefit to outdoor activity for slowing myopic progression. It also found that near work "had little meaningful effect on the rate of myopia progression."

Jeremy A. Guggenheim, Kate Northstone, George McMahon, Andy R. Ness, Kevin Deere, Calum Mattocks, Beate St Pourcain, Cathy Williams. (2012) Time Outdoors and Physical Activity as Predictors of Incident Myopia in Childhood: A Prospective Cohort Study. (ABSTRACT) Ivestigative Ophthalmology & Visual Science VOL 53 no. 6 PG doi: 10.1167/iovs.11-9091

MyopiaPrevention.org comment: Lesser myopia progression was associated with greater time spent outdoors but not necessarily with greater physical activity. Thus it appears that the benefit of being outdoors does not require a higher level of physical activity to exert a beneficial influence on myopia control.

Earl L. Smith III, Li-Fang Hung and Juan Huang. (2012) Protective Effects of High Ambient Lighting on the Development of Form-Deprivation Myopia in Rhesus Monkeys. (ABSTRACT) Ivestigative Ophthalmology & Visual Science January 25, 2012 vol. 53 no. 1 p. 421-428 doi 10.1167/iovs.11-865

MyopiaPrevention.org comment: It was found that form deprivation (a method to induce myopia) in rhesus monkey infants could be significantly prevented from inducing the myopic changes if light levels approximating outdoor illumnination was maintained for six hours during the middle of the daylight cycle. In other words, bright lights slowed or stopped myopia. The conclusion stated that manipulation of indoor light levels may be a method of myopia control.

Justin C. Sherwin, MBBS, Mark H. Reacher, MD, Ruth H. Keogh, Anthony P. Khawaja, MBBS, MPhil, David A. Mackey, MD, Paul J. Foster, PhD. (2012) The Association between Time Spent Outdoors and Myopia in Children and Adolescents: A Systematic Review and Meta-analysis. (ABSTRACT) Ophthalmology published online 20 July 2012 DOI: 10.1016/j.ophtha.2012.04.020

MyopiaPrevention.org comment: Quoting from the Results and Conclusions: "The pooled OR for myopia indicated a 2% reduced odds of myopia per additional hour of time spent outdoors per week, after adjustment for covariates..." "The overall findings indicate that increasing time spent outdoors may be a simple strategy by which to reduce the risk of developing myopia and its progression in children and adolescents."

W Neil Charman.(2011) Myopia, posture and the visual environment. (FULL TEXT) Ophthalmic and Physiological Optics Volume 31, Issue 5, pages 494–501, September 2011 DOI: 10.1111/j.1475-1313.2011.00825.x

MyopiaPrevention.org comment: The "possible role of the peripheral retina" is discussed. The mechanism of oblique astigmatism generating the peripheral signal is mentioned and how that requires a uniform field of equal distances from the eye that is generally present in outdoor environments but is lacking indoors, especially for near tasks with poor posture and head tilts.

Yuval Cohen, Michael Belkin, Oren Yehezkel, Arieh S. Solomon, Uri Polat. (2010) Dependency between light intensity and refractive development under light-dark cycles. (FULL TEXT) Exp Eye Res January 2011, pp 40-46; doi:10.1016/j.exer.2010.10.012

MyopiaPrevention.org comment: Chicks were raised under light-dark cycles with light levels of low, medium and high intensity. Low levels of light were found to be a risk factor for the development of myopia and high light levels were found to be protective against myopia.

Mutti, Donald; Zadnik, Karla.(2009) Has near work's star fallen? (FULL TEXT) Optometry & Vision Science: February 2009 - Volume 86 - Issue 2 - pp 76-78

MyopiaPrevention.org comment: The authors argue for a paradigm shift in the thinking that links near work to myopia. After 400 years, they say it is time to recognize "the inconvenient truth" that the eye is far more responsive to inhibitions to ocular growth (resulting in no myopia) than it is to stimulation of ocular growth. Since reading is a short term activity in relation to the overall visual experience, (except in severe cases where it might actually be a factor) study after study has shown a weak connection between myopia and near work. Thus short term environmental changes, such as two hours a day outdoors, has the ability to significantly reduce the incidence of myopia regardless of the amount of near work involved. Without stating it, the authors are trying to say "Reading does not cause myopia. Probably." A fallen star indeed.

Lim LS, Gazzard G, Low YL, Choo R, Tan DT, Tong L, Yin Wong T, Saw SM..(2010) Dietary factors, myopia, and axial dimensions in children. (ABSTRACT) Ophthalmology 2010 May;117(5):993-997.e4. Epub 2010 Jan 15.

MyopiaPrevention.org comment: Higher saturated fat and cholesterol intake are associated with longer axial length eyeballs, a significant indicator of degree of myopia.

Mutti DO.(2010) Hereditary and environmental contributions to emmetropization and myopia. (ABSTRACT) Optom Vis Sci. 2010 Apr;87(4):255-9.

MyopiaPrevention.org comment: Emmetropization happens as the eye grows in childhood and the lens thins, the thinner lens compensating optically for the longer eyeball. The thinning appears to be due to the lens being stretched by the growing eye. If the lens stops thinning and the eye keeps growing, myopia will develop. The author suggests that myopia is caused by the thickened lens of the myopic eye restricting growth at the front of the eye so that the lens stops stretching. The eye continues to grow however as the child matures, but now elongates instead of an even increase in size, resulting in myopia. Thus "interruption of equatorial expansion" causes myopia. Their study of 262 babies which showed that babies with the poorest accommodative response also showed the least robust emmetropization. The author believes that "the visual signal for emmetropization is the degree of the accommodative response rather than hyperopic defocus. This hypothesis is, of course, at odds with the numerous animal studies suggesting that hyperopic defocus is the visual signal for infant emmetropization." Emmetropization and myopic development may be two different processes.

Bei Lu, Nathan Congdon, Xiaojian Liu, Kai Choi, Dennis S. C. Lam, Mingzhi Zhang, Mingwei Zheng, Zhongxia Zhou, Liping Li, Xueyu Liu, Abhishek Sharma, Yue Song. (2009) Associations Between Near Work, Outdoor Activity, and Myopia Among Adolescent Students in Rural China. (FULL TEXT) Archives of Ophthalmology 127(6):769-775.

MyopiaPrevention.org comment: A study of 1892 Chinese children, various subgroups of which completed surveys of near-work, time spent outdoors and parental education. Time spent on near-work and time spent outdoors were not associated with myopia. Thus reading was not found to be a risk factor for myopia development while outdoor activity was not found to be protective against myopia.

Dirani M, Tong L, Gazzard G, Zhang X, Chia A, Young TL, Rose KA, Mitchell P, Saw SM. (2009) Outdoor activity and myopia in Singapore teenage children. (ABSTRACT) Br J Ophthalmol. 93(8): 997-1000

MyopiaPrevention.org comment: Outdoor activity resulted in less myopia, independent of other factors such as amount of near work or parental myopia.

Deng L, Gwiazda J, Thorn F.(2010) Children's Refractions and Visual Activities in the School Year and Summer. (ABSTRACT) Optom Vis Sci. 2010 Apr 1. [Epub ahead of print] [cited 2010 Apr 10]

MyopiaPrevention.org comment: 147 children between the ages of 6 and 18 were studied for differences in activities between myopes and non-myopes during the school year and during summer break (June, July and August). Non-myopes spent more hours outdoors each week (10.95 vs 8.25) and less time watching TV (8.91 vs 12.78) compared to myopes during the school year. No such differences were noted during the summer. The abstract is not clear if indoor sports are included in "sports/outdoor activity".

Jacobsen N, Jensen H, Lund-Andersen H, Goldschmidt E.(2008) Is poor glycaemic control in diabetic patients a risk factor of myopia? (ABSTRACT) Acta Ophthalmol. 2008 Aug;86(5):510-4.

MyopiaPrevention.org comment: "The study suggests that myopia may be regarded as a complication of hyperglycaemia in diabetes."

Rose KA, Morgan IG, Ip J, Kifley A, Huynh S, Smith W, Mitchell P. (2008) Outdoor activity reduces the prevalence of myopia in children. (ABSTRACT) Ophthalmology 115(8): 1279-85

MyopiaPrevention.org comment: Higher levels of outdoor time resulted in less myopia. They attributed the effect to brighter light outdoors leading to constricted pupils and thus sharper images with less image blur. They also considered dopamine a potential factor, released in response to bright light by the retina and acting to slow eye growth. Over three thousand students studied.

Konstantopoulos A, Yadegarfar G, Elgohary M.(2008) Near work, education, family history, and myopia in Greek conscripts. (ABSTRACT) Eye (Lond) 2008 Apr;22(4):542-6. Epub 2007 Jan 12.

MyopiaPrevention.org comment: Myopes and non-myopes were studied in young adult men. No attempt was made to determine the refractive error of those who passed the visual acuity screening. It was found that myopes generally had a family history of myopia, were older, more educated, read more and were of higher social class.

Lisa A. Jones, Loraine T. Sinnott, Donald O. Mutti, Gladys L. Mitchell, Melvin L. Moeschberger, and Karla Zadnik (2007) Parental history of myopia, sports and outdoor activities, and future myopia. (FULL TEXT) Invest Ophthalmol Vis Sci. 48: 3524-32

MyopiaPrevention.org comment: Third grade students with greater participation in sports and outdoor activities had reduced odds of being myopic and those with myopic parents were more likely to be myopic five years later. Reading time did not predict future myopia. For those students with two myopic parents, outdoor activity over 14 hours/week reduced the odds of becoming myopic from 60% to 20%.

Chong YS, Liang Y, Tan D, Gazzard G, Stone RA, Saw SM (2005). Association between breastfeeding and likelihood of myopia in children. (SUMMARY) JAMA 293: 3001-2

MyopiaPrevention.org comment: A very small correlation was found that breastfeeding protected against myopia development, but it could not be identified as necessarily a causal relationship. Many such specific questions must be answered before we will have a complete picture of myopia development.

Morgan I, Rose K. (2005) How genetic is school myopia?(ABSTRACT) Prog Retin Eye Res 24(1): 1-38.

MyopiaPrevention.org comment: A discussion of the relative risk of heredity vs environment for myopia development. It is pointed out that in major group of humans studied, the prevalence of myopia is lower in "native" populations but becomes more myopic with urbanization, something termed "myopigenic environments".

Saw SM, Chia KS, Lindstrom JM, Tan DT, Stone RA (2004). Childhood myopia and parental smoking. (FULL TEXT) Br J Ophthalmol. 2004 July; 88(7): 934–937.

MyopiaPrevention.org comment: Parental smoking does not appear to significantly affect the development of a child's myopia.

Cordain L, Eades MR, Eades MD.(2003) Hyperinsulinemic diseases of civilization: more than just Syndrome X. (FULL TEXT) Comp Biochem Physiol 2003 Sep;136(1):95-112.

MyopiaPrevention.org comment: Well worth reading, even if you don't understand it all. (When they speak of "secular trends", they are using the definition of secular that means "long term".) Basically, the article makes a strong case that "high-glycemic-load carbohydrates", which are 36% of the typical US diet, combined with susceptible genes cause a chemical cascade that leads to unregulated growth of many tissues throughout the body, including the sclera, leading to more myopia. The link (where the article can be read)is to The Paleo Diet web site whose premise is that our diet is the reason for many of our health problems.

Cordain L, Eaton SB, Brand Miller J, Lindeberg S, Jensen C (2002). An evolutionary analysis of the etiology and pathogenesis of juvenile-onset myopia. (FULL TEXT) Acta Ophthalmol Scand. 80: 125-35

MyopiaPrevention.org comment: Chronic hyperinsulinaemia (too much insulin in the blood) related to the modern diet may play a key role in myopia progression. An excellent article. Includes a review of rates of myopia in different literate, illiterate, urbanized and rural environments. Basically, near work (such as reading) only produces myopia in urban environments.

Cordain, L.(not dated) Slide presentation: An evolutionary analysis of the etiology and pathogenesis of juvenile-onset myopia. Undated .pdf file on Vision Institute of Canada website. Retrieved May 25, 2010.

MyopiaPrevention.org comment: This is a series of slides illustrating Dr. Cordain's hypothesis that our industrialized food supply is a significant risk factor for the development of myopia. Dr. Cordain is the author of The Paleo Diet.

Donald O. Mutti, G. Lynn Mitchell, Melvin L. Moeschberger, Lisa A. Jones and Karla Zadnik.(2002) Parental Myopia, Near Work, School Achievement, and Children’s Refractive Error. (FULL TEXT) Investigative Ophthalmology and Visual Science 2002;43:3633-3640.

MyopiaPrevention.org comment: Both heredity and near work are associated with myopia, but "heredity is by far the more important factor." They "also found no evidence to support two alternate theories, either that children with myopia resemble their parents because they do more near work or that they inherit a susceptibility to the environment." Environment in this context is meant to be near work (reading). "In contrast to the concerns of parents, watching television, playing video games, or working on a computer at home were not associated with myopia." Studying and reading for pleasure had the strongest association with myopia of different near-work activities but the association was weak compared to whether the parents were myopic.

Earl L. Smith, III, Li-Fang Hung, Chea-su Kee and Ying Qiao.(2002) Effects of brief periods of unrestricted vision on the development of form-deprivation myopia in monkeys. (FULL TEXT) Investigative Ophthalmology and Visual Science. 2002;43:291-299.

MyopiaPrevention.org comment: Infant monkeys were fitted with diffuser (fogged) lenses and developed myopia, as expected. But if the diffuser lenses were removed one hour a day, allowing normal vision, the myopia was reduced by over 50%. Two hours reduced myopia more and four hours nearly eliminated the myopic shift. This effect has also been found in chicks and tree shrews. Brief intervals of clear vision are enough to prevent myopic progression caused by form deprivation, something that may be very important in human myopic development.

Seang-Mei Saw, Hui-Min Wu, Benjamin Seet, Tien-Yin Wong, Eric Yap, Kee-Seng Chia, Richard A Stone, Lionel Lee. (2001) Academic achievement, close up work parameters, and myopia in Singapore military conscripts. (FULL TEXT) British Journal of Ophthalmology 2001;85:855-860

MyopiaPrevention.org comment: Risk factors for myopia were most associated with educational level but not with close up work activity, such as reading. In spite of this and other similar findings, "the strong epidemiological associations of myopia with educational exposure on both individual and societal levels, with higher socioeconomic status and with advanced societal economic development all have made it difficult for investigators to reject the role of close up activity in myopia pathogenesis." In other words, the tendency is to want to assume that since people who are more educated are more myopic then myopia must be caused by reading, but different studies have actually failed to find that link.

Zhan MZ, Saw SM, Hong RZ, Fu ZF, Yang H, Shui YB, Yap MK, Chew SJ.(2000) Refractive errors in Singapore and Xiamen, China--a comparative study in school children aged 6 to 7 years. (FULL TEXT) Optometry and Vision Science June 2000 - Volume 77 - Issue 6 - pp 302-308

MyopiaPrevention.org comment: Chinese students from three different areas were studied for prevalence of myopia. The highest rates were found in the cities, the lowest in the countryside. Since the groups were all students with similar reading habits and genetics, the difference in myopia rates is postulated to be something environmental besides these two factors.