This is a very good question. When parents bring their child to me for an exam, they frequently come in with knowledge that their child is having difficulty seeing at a distance. They may observe that their child squints to see the TV or is unable to see signs and buildings while in the car. After a comprehensive eye and vision exam I will often explain that, yes, they have myopia and I can improve their child's distance vision with glasses. However, there may also be additional visual problems that need to be addressed to improve overall visual function. Sometimes the best way to treat these distance visual problems is with reading glasses. This diagnosis frequently confuses parents. Hopefully this post will help explain why it is necessary.
First, let me explain what types of lenses I am talking about. If a person needs a different lens power for distance viewing than near viewing, then he or she needs either multiple pairs of glasses or a single pair with multiple lens powers. If someone opts to have the all-in-one type, it can be either a bifocal lens (with a line separating the two lenses, distance on the top and reading on the bottom) or a progressive lens (where there is no visible line and the distance lens gradually blends into the near lens).
Which option a patient uses depends on the situation. For example, if a patient needs no distance lens, then one pair of reading glasses is sufficient. If a patient is too young to use a progressive lens, then a bifocal lens is best. (For the sake of simplicity, I am going to use the words "reading glasses" in the article to mean any of these options.)
Usually a child does not need reading glasses for the same reason that an adult does. When people reach about 40 years of age, they need reading glasses because printed matter has become blurry. Their eyes no longer have the focusing power to make the words clear. Children, on the other hand, usually do have enough focusing power to make words clear. But sometimes it may be difficult or uncomfortable for them to read without developing eyestrain, headaches, or blurry distance vision. (This is called accommodative insufficiency.) Although reading glasses help relax the eyes, making it easier to read without eyestrain, they usually do not solve the underlying problem. Often vision therapy is required to truly solve the focusing problem.
The other main reason that children need reading glasses is that their eyes tend to turn inward a little too much. This tendency to turn in can sometimes be controllable on the child's part -- a condition called esophoria, which doesn't cause visible changes in the eye but can result in eyestrain or double vision. In other cases, the child cannot control the tendency, resulting in a visibly drifting inward eye (called accommodative esotropia). In both cases, reading glasses will reduce the eyes' tendency to turn inward. This will relieve the strain on the eyes and may make reading more comfortable.
Also remember that these conditions do not just occur in children. Sometimes adults develop these types of problems and need reading glasses. Also, for both children and adults, sometimes multifocal contact lenses can be used, but patients still need to have appropriate backup glasses.brig
One final note: All children must have shatter-resistant lenses. These are made of Trivex or polycarbonate. We also recommend a sturdy, easily adjustable frame. All of our frames have a warranty against breakage, but it can be a good idea to have a backup pair in case of loss.
Nathan Bonilla-Warford, OD
Bright Eyes Family Vision Care & Bright Eyes Kids
Photo credit. Liz West at Flickr.