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Christmas is one of the most joyful times of the year... thoughts of cookies, decorations, family gatherings, and toys abound. Birthday parties for kids add to the list of wonderful memories as well. But there are a few toys that may not make memories so fun because of their potential for ocular harm. The American Optometric Association lists dangerous toys each year to warn buyers of the potential harm to children’s eyes that could occur because of the particular design of that toy.

Here is a sample of that toy list:

• Laser toys and laser pointers, or laser sights on toy guns pose serious threat to the retina, which may result in thermal burns or holes in the retina that can leave permanent injury or blindness. The FDA’s Center for Devices and Radiological Health issues warnings on these devices at Christmas peak buying times.
• Any type of toy or teenage gun that shoots a projectile object. Even if the ammo is soft pellets, or soft tipped it can still pose a threat. Even soft tipped darts are included in this harmful toy list. A direct hit to the eye can be debilitating.
• Any toy that shoots a stream of water at high velocity can cause damage to the front and or back of the eye. The pressure itself, even though its just water, can damage small cells on the front and back of the eye.
• Any toy that shoots string out of an aerosol can can cause a chemical abrasion to the front of the eye, just as bad as getting a chemical sprayed into the eye.
• Toy fishing poles or toys with pointed edges or ends like swords, sabers or toy wands. Most injuries occur in children under 5 without adult supervision and horseplay can end up in a devastating eye injury from puncture.

The point is, that there are so many great toys to buy for children that can sidestep potential visual harm, that it behooves one to be aware of pitfalls of certain dangerous toy designs.

A great resource of information comes from World Against Toys Causing Harm.

For more information and for this year's list of hazardous toys, visit the W.A.T.C.H. website.

One of the most commonly asked questions in an eye exam comes right after the refraction, or glasses prescription check: “What is my vision?”

Almost invariably, people know the term “20/20”. In fact, it’s a measure of pride for many people. “My doctor says I have 20/20 vision.” Or, on the other side of that same coin, having vision that is less than 20/20, say 20/400, can be a cause of great concern and anxiety. In this discussion I will describe what these terms actually mean.

To lay the foundation, let’s discuss some common terms. Visual acuity (VA) is clarity or sharpness of vision. Vision can be measured both corrected (with glasses or contact lenses) and uncorrected (without glasses or contact lenses) during the course of an eye exam. The result of an eye exam boils down to two different but related sets of numbers: your VA and your actual glasses prescription.

The notation that doctors use to measure VA is based off of a 20-foot distance. This is where the first 20 in 20/20 comes from. In Europe, since they use the metric system, it is based on meters. The 20/20 equivalent is 6/6 because they use a 6-meter test distance. The second number is the smallest line of letters that a patient can read. In other words, 20/20 vision means that at a 20-foot test distance, the person can read the 20/20 line of letters.

The technical definition of 20/20 is full of scientific jargon - concepts such as minutes of arc, subtended angles, and optotype size. If you’d like to read more of the technical details there is a well-written article with illustrations by Dr. John Ellman, you can find here.  For the purposes of our discussion here I’ll try to explain it in less technical terms.

“Normal” vision is somewhat arbitrarily set as 20/20 (some people can see better than that). Let’s say you have two people: Person A with 20/20 vision and Person B with 20/40 vision. The smallest line of letters that person B can see at 20 feet is the 20/40 line.  Person A, with “normal” 20/20 vision, could stand 40 feet away from that same line and see it. There is somewhat of a linear relationship in that the 20/40 letters are twice the size of the 20/20 letters and someone with normal vision could see a 20/40 letter at twice the distance as the person with 20/40 vision.

So how does this translate to a glasses prescription?

Eye doctors can often estimate what your uncorrected VA will be based on your glasses prescription. This works mainly for near-sightedness. Essentially, every quarter step of increasing glasses prescription (i.e. -1.25 as compared to -1.50) means a person can see one less line on a VA chart.

A prescription of - 1.25 works out to roughly 20/50 vision, -1.50 to 20/60 and so on. Anybody with an anatomically sound eyeball, meaning the absence of any kind of disease process, should generally be correctable to 20/20 with glasses or contact lenses. It is important to note, however, that rarely a person’s best corrected VA may be less than 20/20 with no noticeable signs of disease.

Far-sightedness is more difficult to estimate because it is affected by a number of other factors, including one’s age and focusing ability. But that’s a topic for another article.

So there you have it! Hopefully this has shed some light on what these measurements that we take actually mean, and it has allowed you to understand your eye health a little bit better.