Reading causes Myopia or Hyperopia inhibits reading?
There are basically two schools of popular thought when it comes to how myopia (nearsightedness) develops. You basically have the eye doctors on one side and the natural vision people on the other. Most doctors and others in the first group believe that myopia is primarily caused by genetic factors. There are many studies to back up this idea. The natural vision people believe that myopia is caused by close work with no genetic factors. Many of these people practice methods like the Bates Method, which teaches to relax your eyes and "learn" to see better. Both sides claim to have their respective scientific studies backing their claims up. Others, in the middle, think there are both behavioral and genetic influences involved.
If you perform a quick Google search, you will find a lot of contradictory information, from both of these schools. I found that no one vehemently denies any behavioral factors, while many sites will write off genetic factors completely with little or no hard evidence. This was my first clue that the studies finding a genetic link have probably been conducted scientifically, and that the ones blaming behavior just don't have as much science behind them as I would like (if any). This site was pure comedy. Although I think they are completely ridiculous, I don't actually want to get into this fray - the thing that bothers me is that there are very few pop culture references to the idea that being myopic could predispose people toward reading (equivalently, being hyperopic may provide some inhibition for reading much). This isn't to say that reading definitely doesn't contribute at all to myopia, but the established correlation between heavy readers and myopics may have something to do with the fact that it is easier to read when you are an uncorrected myopic.
Sites like the one above use the statistic that 90% of college students in Asian countries are myopic to support the claim that the readers must become myopic through the close work of reading. This statistic may also be partially explained by the idea that in such an academically competitive culture, the non-myopic people are filtered out. As I described on another page, I have personal experience from a LASIK surgery which has shown me just how much easier it is to read for long periods when you are myopic rather than hyperopic (farsighted).
Most elementary schools I know of test for myopia, since this is fairly easy to do. It is much more difficult to test for hyperopia, since chart tests can miss hyperopia and reliable testing involves objective (non verbal response) measures like retinoscopy and refraction. There are plenty of sites like this one which give a lot of factual information about different refractive errors. I know I was never tested beyond the simple chart test in school, and I am not sure of the percentage of elementary schools who use retinoscopy to test for hyperopia. I do know that not just anyone unqualified can practice this method, so it seems unlikely many schools actually use it.
Without reliable tests for hyperopia, we are left with a large percentage of children with undiagnosed hyperopia. Many statistics I've found put the figure at 25%(EyeSTAR LASIK Institute) of the population, although most of these comes from LASIK centers. A recent study1 claims 10% of adults over 40 in the U.S. are hyperopic, and another in Spain claims around 37% of children 3-8 are hyperopic there2. So there's some discrepency, but from what I know personally about the difficulty of reading with hyperopic eyes, I know that if I had been a hyperopic child who remained undiagnosed it would have been difficult to spend a great deal of time reading at night. This was something I loved to do as a myopic child. Furthermore, if I had been hyperopic I would have been unable to explain or complain about the problem, because as a young child I would have believed that it was just regular vision. I mean, I couldn't read the board at school and it took more than a year for me to communicate the problem to my parents. Something as subtle as a reading fatigue would most likely be confused with "well, i guess he just doesn't like to read."
The implications of all this are that people who can read easier will like to read more. People who have more physical trouble reading will like to read less. It's no secret that activities seem more rewarding when we can perform them well. So the myopics will do more reading as children (in general), putting them on average above the academic curve. The hyperopics will do less reading and close work, inhibiting their learning (which is based in reading). The end result? In academic competition the myopics will win. So at your average competitive college look around you. Those glasses and contacts on so many may not be caused by all the hard work those students have done, but rather the myopia as young children got them reading and helped get them on a solid academic track.
With all the information that's out there, there is little information and few (if any) accessible studies that explicitly mention the possibility that myopia could be a cause of reading to explain the large correlation between the two. Even in the "facts" is always present the statement that the correlation is sometimes explained by experts who think reading contributes to myopia. Lots of times the scientific findings are distorted a bit by the news.
- A authoritative web page, with an account of myopia which also mentions the possibility that close work causes myopia while ignoring the other possibilities
- Another article aimed at parents warning against close work (took a screenshot of the article, the original is gone)
- Good page and fact based. The causal relationship between close work and myopia is again mentioned.
- Another study3-based article providing only one possibility for the causality. This is a case where the title of the article biases you in advance of hearing about the research at all: "Reading can damage eyes"
There are also the people who believe in self correction without glasses or lenses, who all believe close work is the sole cause of myopia, many who publish webpages looking for converts. No science here, as far as I can tell.
- An interactive approach to eye "disease" treatment. Just relax to solve that vision problem caused by reading, and stare off into the distance.
- More biased information about the Bates Method
- Blindness is all in your imagination
- A guy who is convinced that reading caused his myopia
The following are pages which are especially relevant to the possibility that myopia helps children want to read and hyperopia influences them not to enjoy reading.
- A few years ago the idea that night lights cause myopia was contradicted by a study4.
- An unassuming look from a practical point of view. Points out that the famous Eskimo study5 cited by all the crazies who want you to buy their fancy headgear may not be believable due to poor sampling.
- A recent study which puts heredity as the main cause of myopia. Interestingly, it also finds a link for reading but not for computer use.
So what do I propose? What do I want from this? Right now everyone studies myopia and close work. If we can't start testing and correcting for hyperopia in elementary schools, the other possibility for the correlation needs to get out there to counter the commonly held (unproven) beliefs. I want someone to do a high profile study which explores the link between academic problems and uncorrected hyperopia, and I want to see the study appear in the popular press. If there is such a correlation found in the study, I want to see the idea put forth that parents should get their children tested for hyperopia if they notice a lack of interest in reading in their children. Done in 25% of academically inhibited children, corrected for reading would make nothing less than a sweeping difference in the academic abilities of our children. But the whole point of this is so that parents will get their kids tested for hyperopia and be vigilant for signs that their kids are having trouble reading. After my experience I surely will be conscious of it.
Update: I was doing a literature search the other day, and came across this study, which basically performs the study I wanted to see. The study6 found a correlation between hyperopia and poor performance in school in all grades. Funny the popular press never really made a big deal about this.
- Kempen JH, Mitchell P, Lee KE, Tielsch JM, Broman AT, Taylor HR, Ikram MK, Congdon NG, O'Colmain BJ; Eye Diseases Prevalence Research Group. The prevalence of refractive errors among adults in the United States, Western Europe, and Australia. Arch Ophthalmol. 2004 Apr;122(4):495-505.
- Montes-Mico R, Ferrer-Blasco T. Distribution of refractive errors in Spain. Doc Ophthalmol. 2000 Jul;101(1):25-33.
- Saw SM, Hong CY, Chia KS, Stone RA, Tan D. Nearwork and myopia in young children. Lancet. 2001 Feb 3;357(9253):39
- Smith EL 3rd, Bradley DV, Fernandes A, Hung LF, Boothe RG. Continuous ambient lighting and eye growth in primates. Invest Ophthalmol Vis Sci. 2001 May;42(6):1146-52.
- Young FA, Leary GA, Baldwin WR, West DC, Box RA, Harris E, Johnson C. The transmission of refractive errors within eskimo families. Am J Optom Arch Am Acad Optom. 1969 Sep;46(9):676-85
- Krumholtz I. Results from a pediatric vision screening and its ability to predict academic performance. Optometry. 2000 Jul;71(7):426-30. Erratum in: Optometry. 2000 Aug;71(8):489.