The simple answer is yes. And no. Ok, this may not end up being such an easy question to answer, and here is why. Basically there are three main types of vision ailments that most children have. For simplicity sakes, these are myopia, hyperopia, and astigmatism. Let’s take a look at each of these three conditions in more detail to see how they are diagnosed, and to get more insight into how a screening may or may not detect them.
Myopia is also know as nearsightedness. Typically the patient states that they see better at near than at far (though with high levels of myopia this may not hold true). The person doing the screening will quickly be able to determine that the person can’t read a certain line of letters at a fixed distance away, and will flag the student as a FAIL. So far so good right?
Hyperopia is the next condition, also known as farsightedness. This condition is a little trickier,to understand than mypopia because most children have a little cheat mechanism built in to their eyeball that can overcome small to moderate amounts of hyperopia. Mypopic children can not do the same thing as hyperopic children (aka cheat, or in scientic terms they accommodate). So now the screeing person will note that the child can see very well at far, and quite well at near – but there can still be a problem. Confused? Let’s try this another way. The moment a hyperopic child wakes up in the morning, their brain (in order to prevent blurry vision, which would have been there because of the hyperopia) uses a special accommodative system in the lens of the inner eye to activate so that it can clear the world up. It’s kind of like flexing your bicep muscle all day long. Eventually we know that the muscle will probably fatigue. And this is exactly what can happen with children who are hyperopic. They go to school, read books, do research, do homework with their eye muscles working extra hard. Once the point of fatigue is reached, the children will often stop doing anything strenuous and try to relax or look far away. So hyperopia ends up being a problem of eye fatigue after prolonged near work, and not a problem of not being 20/20. This is an important distinction. As you may then imagine, many students with hyperopia simply will not get picked up by the vision screener because they “pass” since they may see 20/20.
The next group of patients are ones with astigmatism. Astigmatism is when the stuctures of the eyeball do not create a uniform, clear image at the retina due to certain parts of the cornea or lens not being perfectly spherical in shape. This creates distorted vision, and astigmatism may be found alone, with hyperopia, or with myopia. For sake of simplicity, we will discuss astigmatism alone since we already spoke about mypopia and hyperopia in the last two sections. Astigmatic patients at really high levels will usually have enough distortion to cause letters at a distance to become blurred – but this may not always be the case since some of the high astigmatic patients can squint their eyes to allow them to clear up letters. If the vision screener is not paying attention, they may miss this important sign. At low levels, many astigmatic patients may still have adequate vision to make out distance letters on an eye chart. However, having any amount of astigmatism may adversely affect reading efficiency in young children since the lens inside the eye doesn’t know whether to accommodate (flex) or unaccommodate (relax). These patients will be more likely to have reading difficulties if corrective lenses aren’t given. So once again, as in the case of hyperopia, astigmatic children undergoing a vision screening who actually have an issue may not be identified.
So we can hopefully see now that the vision screening provided by schools or pediatric offices will usually correctly identify myopic children; but usually will not identify hyperopic and astigmatic children. A week doens’t pass by in one of my offices without having a parent bring their child in complaining that their child has struggled in school for years and years, and after examining their child s/he is found to have hyperopia or astigmatism. When I question these parents as to why they hadn’t come in earlier, they often will state, “My child passed the school screening, I didn’t think there was a problem”. It can only be imagined how those childrens’ lives would have been different if they had a better shot at excelling in school; concentrating on their homework without visual strain; or being able to look back and forth from distance to near without seeing blurry. The school and pediatric screenings are mainly MYOPIA SCREENINGS, and the wording on their concent forms should clearly state this. It would be great if all students were required to have an eye exam by an optometrist or ophthalmologist, but many states do not have the funding to allow this.
Either way, make sure your children get an eye exam, and take the screenings with a grain of salt since they are mainly trying to rule out one, and only one, out of three refractive eye conditions.