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True or False – Reading in low light damages vision?

Posted on April 23, 2013



I wasn’t much of a reader when I was growing up, but my children devour books like they are Willy Wonka chocolate bars.  On more than one occasion I’ve quietly snuck up to my children’s bedrooms (after the time they were supposed to be sleeping) and have discovered them reading in practical darkness next to a small nightlight, or reading under their covers with flashlights.  Such discoveries can worry parents.  Many kids have been admonished for reading in low light conditions because their parents believe that it can damage vision.  However, this has never been supported by research.  In an article entitled Myopia: the nature versus nurture debate goes on published in the Journal Investigative Ophthalmology & Visual Science (1996), the authors note some environmental factors that can lead to myopia, but reading in low light conditions was not one of them.  When you think about it, people used to read by candlelight by necessity, and there is no evidence that it damaged their eyesight.  Reading in low light, like sitting too close to the television, can lead to eyestrain, where the eyes can become red, irritated, watery, blurry, and dry.  But eyestrain usually only lasts for a short period of time and doesn’t result in vision damage.  Our eyes are pretty incredible and allow us to see in a variety of environments.  When in low light conditions, our eyes make a variety of adjustments to help us see better.  These adjustments include pupil dilation, the production of certain chemicals to make our eyes more sensitive to light, as well as the nerves on the retina becoming more receptive to light.  If you have to read in low light conditions, take breaks every 15 to 30 minutes and try to remember to blink often as this will likely help reduce the chances of your eyes getting tired and irritated.

Mutti D, Zadnick K, Adams A: Myopia: The nature versus nurture debate goes on. Investigative Ophthalmology & Visual Science (1996), Vol 37, 952-957.

True or False – Sitting too close to the TV can damage your vision

Posted on April 16, 2013


image30I would almost be willing to wager that every single person reading this post has at one point in their childhood been instructed by their mother or father to back away from the television set, or risk going blind.  It has long been thought that sitting too close to the television can damage vision.  Turns out mothers and fathers aren’t the only ones who believe this falsehood.  I came across one study that reported even teachers and school children in Pakistan believed that watching television can damage vision.  It is true that many years ago some referred to the television as the radiation box.  Prior to 1968 televisions did emit low levels of x-rays, but I couldn’t find any studies linking television watching, even back then, to eye damage.  The television sets of today do not emit x-rays or any radiation.  So, watching SpongeBob up close on Saturday morning won’t damage your child’s vision, but most eye experts agree that it can cause eyestrain.  Signs and symptoms of eyestrain can include red, itchy, burning, watery eyes, as wells as blurred vision.  These signs and symptoms may be uncomfortable, but will usually subside or disappear in an hour if one stops watching television.  Think about adults who stare at a computer screen up close for far too many hours a day.  I’ve found no evidence that would suggest this cause’s eye damage either.  The American Academy of Ophthalmology even reports that many kids can focus on close items better than adults.  Watching television doesn’t damage vision, but research has shown (Toyran et. al, 2002) that too much television viewing contributes to obesity, headaches, back pain, and sleep problems.  It’s probably a good idea to stay at least 5 feet back when watching television, and if you notice your child inching closer to the set take them in for an eye exam as that could be an indicator of nearsightedness.

Toyran M, Ozmert E, Yurdakok K: Television viewing and its effect on physical health of schoolage children. The Turkish Journal of Pediatrics (2002), Vol. 44, pps 194-203.

True or False – Marijuana gives you the munchies?

Posted on April 9, 2013


Marijuana (also known as Cannabis) has been grown and consumed for thousands of years.  There are reports that marijuana was used as early as 300 AD in India to help stimulate the appetite in individuals who for whatever reason had lost the desire to eat.  Keep in mind that using marijuana is illegal, unless prescribed by a physician (currently 13 states have legalized medical marijuana use).  Marijuana has been shown to be an analgesic (pain reducer), has been used in the treatment of glaucoma (lowers intraocular pressure), and helps relieve nausea and vomiting.  Early studies that were conducted in the 1930’s which examined whether marijuana stimulated appetite, were not always high quality studies.  However, as the recreational use of marijuana increased in the 1960’s so did the interest in conducting high quality studies (e.g., studies that used control groups and attempted to standardize the doses of marijuana consumed).  Most of the studies conducted support the idea that marijuana does in fact give you the munchies (stimulates appetite).  The authors of one study (Cota et. al., 2003), which was published in the International Journal of Obesity state “Despite the public concern related to the abuse of marijuana and its derivates, scientific studies have pointed to therapeutic potentials of Cannabinoid compounds and have highlighted their ability to stimulate appetite, especially for sweet and palatable food”.  This may be why marijuana use is thought to be helpful for patients with decreased appetites due to illnesses such as AIDS or late stage cancer, and it may be the reason people joke about taking late night runs to Taco John’s after consuming marijuana.  It is believed that the active ingredient in marijuana (THC) is similar to chemicals in the body which are released when your stomach is empty with the purpose of telling the brain it is time to eat.

Cota D, Marsicano G, Lutz B, Vicennati V, Stalla G, Pasquali R, & Pagotta U: Endogenous cannabinoid system as a modulator of food intake.  International Journal of Obesity (2003), Vol 27, pp. 289-301.

True or False – Pesticide residue on foods cause cancer?

Posted on April 1, 2013


There is no question that pesticides are dangerous.  After all, the purpose of pesticides is to kill pests.  Millions of people each year get sick from pesticide exposure and thousands are killed.  However, most of those who get sick do so because they work with (e.g., produce, transport, apply) pesticides and not because they are exposed to pesticides on the foods they eat.  Some people take the idea of pesticide residue on foods very seriously.  I realized this one afternoon as I watched a woman at a park rinse and carefully wipe off grapes one by one before she ate them.  Survey research tells us that many people believe that pesticide residue on food increases their risk for cancer.  Pesticides are strictly regulated.  The Environmental Protection Agency sets safety standards, known as tolerances, for how much pesticide residue can be on foods.  The California Department of Pesticide Regulation (CDPR) reports that most crops are treated with pesticides.  Those pesticides not only allow farmers to grow crops in areas that might not otherwise be suitable, they also result in higher crop yields, and extend shelf life of products.  The CDPR also report that there is no pesticide residue on about 60% of the produce they test and that only about 1% of their test samples have pesticide residue levels that are too high.  They also state that years of monitoring show that most fruits and vegetables have little or no detectable residue by the time they reach market, and even less by the time they are washed and served.  Lois Gold and colleagues (1997) in an article titled Pesticide residues in food: investigation of disparities in cancer risk estimates state “Using standard methodology and measured dietary residues in the total diet study, the estimate of excess cancer risk from average lifetime exposure to synthetic pesticide residues in the diet appears to be less than one-in-a-million for each of the ten pesticides for which adequate data were available.”

Gold L, Stern B, Slone T, Brown J, Manley N & Ames B: Pesticide residues in food: investigation of disparities in cancer risk estimates. Cancer Letters (1997), Vol 117, pps 195-207.