Convergence Insufficiency Study
One of the more common vision problems associated with reading difficulty is called convergence insufficiency. You converge your eyes when you move your eyes inward to view something close to you. Conversely, you diverge your eyes when you move them apart to view something at a distance. Many children with reading problems have trouble converging. They either can’t converge enough to be comfortable with print, or if they can do so, they can’t sustain the effort during the long periods they are expected to read. Either situation is called convergence insufficiency.
Description of the Study
A Randomized Clinical Trial for Treatment of Convergence Insufficiency in Children, found in the Archives of Ophthalmology, January 2005, compared three treatments for convergence insufficiency. The treatments were 1) office-based vision therapy combined with home exercises between visits, 2) pencil push-ups done at home and 3) a placebo office treatment that mimicked the vision therapy treatment but used eye exercises that wouldn't address convergence insufficiency.
Note: The article in the journal used to be accessible online, but no longer is without a subscription or other access. Here is a link to a pdf of the article on a different site. (At least it's available as of early 2019.) It will open in a new tab so you can reference it as you read the rest of this page.
Symptoms of Convergence Insufficiency Suggest Reading Problems
First, scroll down to the third page of the article (page 16 of the study) where you will find a chart with fifteen items on it. As you read the questionnaire you will see the sort of issues a child with convergence insufficiency will experience. If your own child is experiencing many of them, you or your spouse also probably experienced them when you were learning to read, particularly if one of you struggled in the early grades of school.
Note: The way the questionnaire was used was to assign a number from 0 to 4 depending on the answer. ("Never" gets a 0, "Not Very Often" gets a 1, up to "Always" gets a 4.) The maximum possible score is 60 (all 4's) and a patient was considered to be showing symptoms of convergence insufficiency if his score was above 16.
Treatments for Convergence Insufficiency
The article states that pencil push-ups is the most commonly prescribed treatment for convergence insufficiency, but that is because many optometrists do not refer patients to vision therapy departments. In other words, pencil push-ups is the main tool in their tool kit with which to address convergence insufficiency. Developmental optometrists, however, are not only more likely to diagnose convergence insufficiency but they also routinely refer patients to vision therapy if they find it. So, in essence, the point of the study is to determine whether both groups of eye-care specialists, those who refer to vision therapy and those who don't, are effectively addressing the problem.
Besides the symptom questionnaire, two objective measurements were taken. The first was the near point of convergence, which just describes how close you can focus. If your child has great difficulty focusing at all on near objects, any eye-care professional should pick up on it. The second measurement was positive fusional vergence. This is measured by having your child focus on an object at a comfortable distance and then placing prisms in front of each eye which force him to converge his eyes to maintain focus. While I’m not sure, I suspect that this test is harder because the changing of the prisms forces your child to make step adjustments in his convergence, which would be harder than smoothly converging to a near point as in the first test. Both tests, however, measure your child’s ability to focus both eyes together simultaneously on close work.
I should mention also that developmental optometrists, if they suspect a vision problem of this nature, will also do more extensive testing to determine whether your child can sustain the effort. Many children can perform at adequate levels on a convergence test the first time, but if you have them try to do it several times in a row, they gradually lose their ability to converge. If your child starts out reading smoothly, but is struggling like a non-reader after a page or two, this might be why.
Results of the Study Presented Graphically
So, the questionnaire covered symptoms and the two tests measured convergence ability. The primary outcome measure was the symptom score on the chart discussed above.
Now scroll down a few more pages to the outcome chart at the top of page 20 of the study. There you will see that the starting symptom scores for each of the three groups were around 30. After twelve weeks, the pencil push up group and the placebo group both had lower symptom scores, at around 25, but the office-based-vision-therapy group had an average symptom score of only 9.5, well below the score of 16 that indicates a problem with convergence insufficiency. The chart right below that one displays the results in graphic form.
If you look at the other two graphs (Figures 5 and 6), you'll see that only the vision therapy group had the two objective measures of convergence ability move into the normal range, indicating that not only were symptoms diminishing in that group, but that their physical ability to converge their eyes had improved to levels considered normal.
The Placebo Effect
The placebo arm of this study was valuable for a couple of reasons. First, note that both the placebo group and the pencil-push-up group also improved their symptom scores on the survey as the study progressed. Given that it's question and answer survey, it's likely that participants might feel they were improving after all the work they were doing, and reported less symptoms.
But what about the improvement in the objective measures, the eye testing? Here, because participants were selected based partly on failing those tests initially, some would likely have had better scores if tested on another day. They might not even have qualified for the study. In other words, those having a bad vision day were more likely to be included in the study. When their vision skills were tested later, they might have been having a normal day, not a bad day, visually.
But the key information to draw from the placebo group is that the pencil-push-up group, while it improved on all measures, did no better than the placebo group. Without the placebo group's results to compare with, one might be able to argue that the pencil push ups worked, just not as well as vision therapy. And, given the cost difference (free versus a lot), one might have been able to justify prescribing pencil push ups to address convergence insufficiency.
Update: Results of a Larger Study
The study discussed above had a small group of participants. It was a precursor to a larger study that was finally reported in 2008 in the same journal. This new study, titled Randomized Clinical Trial of Treatments for Symptomatic Convergence Insufficiency in Children, (the link as of early 2019 was to the complete article) covered over two hundred patients and also added a fourth group that used a home-based computerized vision therapy program designed to train convergence skill. Again, the Office Based Vision Therapy group was the only group that experienced significant relief of symptoms. Plus, this was a "gold standard" study where cause and effect could be legitimately determined. The main results table is in Table 3 on page 1343.
If your child exhibits many of the symptoms on the questionnaire in the study discussed above (or on the Vision Assessment Checklist on this site) and struggles with reading, you should see a developmental optometrist unless your family optometrist routinely assesses this sort of problem and also routinely refers to a vision therapy department. This last part is the key. If your family optometrist diagnoses convergence insufficiency, but does not refer to vision therapy, your child might not be getting the help needed to correct the problem.
Convergence insufficiency is a major impediment both to learning to read and to reading comfortably later in life. Vision therapy has now been shown to address it. Furthermore, during a course of vision therapy, several other potential vision issues are also treated. I cannot emphasize strongly enough, if you have a child struggling with reading, you need to at least rule out the possibility of problems with vision skills before assuming his vision is "just fine," a comment I've heard dozens of times from parents when I've suggested vision might be an issue.
You do this by locating a developmental optometrist in your area and getting your child tested. The page Find a Vision Therapy Provider can help you do that.
The next page discusses a common phenomenon observed by vision therapists when a child has poor convergence skills. Alternating Suppression is the brain's mechanism for keeping both eyes in the game while a child is attempting to develop convergence ability.