AFF | Awesome Fun Facts

Myth: Reading in a dimly lit area will damage your eyesight.
In fact, the only “damage” reading in a dimly lit setting will do, in comparison to reading in an ample lighted setting, is to cause extra eyestrain, which will go away simply by resting your eyes.  This shouldn’t be too much of a surprise given the fact that for centuries people have been reading by candlelight without rampant reports of rapidly reduced eyesight.  In fact, the opposite has happened with rates of things like myopia, usually what is most cited as being what reading in dim light contributes to, being on the rise despite all our bright light sources.  Nonetheless, perhaps because parents the world over are trying to get their kids to go to bed, rather than to sneakily try to read by a nightlight or the like, this myth has been widely perpetuated.
It even made it on the list of “Seven Medical Myths That Doctors are Most Likely to Believe”, a list put together by the British Medical Journal, which is in turn owned by the British Medical Association (for the other six medical myths that even doctors sometimes perpetuate, see the Bonus Facts below).  In addition to doctors, 56.3% of teachers surveyed by BioMed Central say that in order to maintain good eye health, people should avoid reading in dim light, despite the fact that to date no scientific study has been able to conclusively show that reading in dim light hurts your eyesight (long term) more than reading in an adequately lit area.
Now it should be noted that people who read a lot or otherwise focus on things close up for long periods of time, such as people who work on computers all day or do a lot of sewing or the like, do have a higher tendency to develop myopia (nearsightedness), but dim lighting doesn’t appear to make this tendency worse, simply that excessive reading seems to contribute to eventually developing nearsightedness.
Why exactly this is the case isn’t yet fully understood, but the correlation is strong enough between groups of people who do a lot of “close-eye work” and their propensity to develop myopia at a drastically higher rate than the average, that most optometrists are prepared to say that “close-eye work” is for some a major contributing factor to developing myopia.  Although, of course, until someone figures out exactly why and proves it in a scientific manner, they can’t say for sure as correlation does not imply causation.  The leading theory, which seems plausible enough, is that the near constant straining of muscles focusing the eye, stretching the eyeball a bit, over the years gradually causes a permanent lengthening of the eyeball, thus the person developing myopia as they age.
Now, reading in dim light does seem to increase eyestrain, so some theorize that this exacerbates the above problem, assuming that theory is correct, but the consensus among optometrists is that if this is what is happening and eyestrain is indeed significantly greater in low-light, it’s very unlikely that the difference is going to be so great that it produces a noticeable acceleration of the development of myopia over reading in a well lit area.
The reason reading in low light is thought to increase eyestrain is because your eyes have to work a lot harder to focus on the words. Your iris is simultaneously trying to open your pupil as wide as possible to let in more light, while your eye is also trying to focus that small amount of light hitting the words onto your retina just right so that you can distinguish between the words and the page itself. According to optometry professor Howard Howland of Cornell University, this is accomplished by your muscles lengthening your eye even more than normal when reading to bring everything into focus.
Whether reading in low-light or ample light for lengthy time frames, the resulting eyestrain is not serious and one simply needs to rest the eyes on occasion. You can do so by periodically taking a break from focusing on something close up, and instead looking at something far away. Specifically as a general rule, optometrists tend to recommend taking a break from focusing your eyes on close up things for a minute or two every 15-30 minutes.  Also, closing your eyes for a minute helps because, while reading, you typically blink about 1/4 the amount you would normally do, so your eyes can get a bit dry.  Trying to train yourself to blink regularly while concentrating isn’t usually feasible, so the eye-closing method tends to work better for most people.
Bonus Facts:

• The other six items on the British Medical Journal list of myths that many doctors still believe are (I’ve already covered several of them on this site, so click the links if you’re interested to know more about each myth):
  • Myth: You Need to Drink at Least 8 Glasses of Water Per Day to Stay Hydrated
  • Myth: You Only Use 10% of Your Brain
  • Myth: Hair and Fingernails Continue to Grow After Death (It’s actually the body tissue contracting that creates this illusion.)
  • Myth: Shaving Makes Your Hair Grow Back Faster/Thicker
  • Myth: Eating Turkey Will Makes You Drowsy
  • Myth: Cellphones used in a normal way create enough electromagnetic interference to cause considerable problems with hospital equipment, creating false alarms, incorrect equipment readings, and subsequent errors in treatment.  This myth was based on a highly publicized study done in 1993 that offered no actual direct evidence that this was happening, just several doctor’s suspicions that it was happening.  An actual scientific study by the Mayo Clinic in 2005 busted this myth, as did another done in 2007.  Not only this, but, funny enough, according to a survey of anesthesiologists, having a cell phone to use while treating patients resulted in about 22% fewer medical errors than when they had to delay communicating with someone about something pertaining to their patient.
• One more myth that didn’t make the above list, but is none-the-less rampant among us non-MD’s is that alcohol kills brain cells.  In fact, if you’ll follow the link, you’ll see that it actually does not, at least, not the amounts of alcohol it is possible for humans to consume without dying.
• Developing Myopia and having a high IQ were at one time thought to go hand in hand, perhaps having some underlying genetic cause.  However, today most don’t think this is the case and it is rather because people with high IQ’s tend to read more, often from studying in academia.  Once again proving the logical precept that correlation does not imply causation.
• Smoking is not only bad for your lungs, but is also bad for your eyes, among other parts of your body.  Particularly, smoking has been shown to increase your risk of cataracts and accelerate macular degeneration.
• Another way to promote good eye health is to eat a lot of fruits and vegetables, particularly those rich in antioxidants, as well as staying away from saturated fats and hydrogenated oils.  This obviously is good for your whole body too, so no surprise that it’s also healthy for your eyes.
• Wearing 100% UV filtering sunglasses anytime you’re outside in the daytime is also extremely good for the long-term health of your eyes.  Even when it’s cloudy out, UV light travels right through the clouds (as clouds are mostly made of water and water is UV transparent) and causes very slight damage to your eyes, which over time adds up.
• The “opposite” of myopia is hyperopia, which is farsightedness.  When eyeballs are too “long” people develop myopia and things that are far away get very blurry, so it’s no surprise that people get hyperopia when their eyeballs are too “short”, so things close up get blurry.
• A third “eyeball shape” vision condition is astigmatism, where the cornea isn’t perfectly round, which in turn results in blurred vision both far away and close up.
• A large percentage of babies are born with hyperopia, but as they grow, their eyeballs lengthen to the correct size.
• There are around 130 million light sensitive cells in your retina, which is only about the size of a postage stamp.