Convergence Insufficiency Study

One of the more common vision problems associated with reading difficulty, or dyslexia if you wish to call it that, is 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 study, located in the Archives of Ophthalmology, January 2005, and available on-line, 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 where exercises not designed to address the problem were conducted to assess any placebo effect.

Note: The journal links in the article below now lead to a subscription-only article because the journal has apparently changed its pricing policy since this page was originally published. Here is a link to a pdf of the same article. It will open in a separate tab so readers can switch back and forth between tabs to try to reference the information discussed below because the links no longer go to the text and tables within the article.

Here is a link to the original article if you wish to read it: Article on Convergence Insufficiency. Note: It will open in a new window or tab, not in this window.

Symptoms of Convergence Insufficiency Suggest Reading Problems

What might interest you even more if you have a child struggling with reading, however, is the questionnaire the study’s authors used to determine whether a person suffered from convergence insufficiency. Here is a link to the questionnaire:Convergence Insufficiency Symptom Survey from Article (Again, it will open in a new window or tab.)

If you read the questionnaire, you might see some of the symptoms your child has been experiencing. In fact, in most cases if your child is experiencing 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 symptomatic if his score was greater than 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 most ophthalmologists and optometrists do not refer patients to vision therapy departments. In other words, pencil push-ups is the only tool in their tool kit with which to address the problem. Developmental optometrists, however, are more likely to diagnose convergence insufficiency and also routinely refer patients to vision therapy. So, in essence, the point of the study is to determine whether each group of eye-care specialists is 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 nearpoint 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. Here are the graphs of the results on each: Again, the links will open in a new tab or window. As it states on the bottom of each graph, PPT=Pencil Push-up Therapy and OBVT=Office-Based Vision Therapy.

Graph of symptoms over the 12 weeks of treatment

Graph of near point of convergence over the 12 weeks of treatment

Graph of mean positive fusional vergence over the 12 weeks of treatment

What you see in the above graphs is that the symptoms diminished to within a normal range for the group getting vision therapy and that two objective measurements of convergence ability also moved to within a normal range in each case for the vision therapy group. This was not true of the group that was prescribed pencil push-ups, nor was it true of the placebo group. Note that the measurement of Positive Fusional Vergence (last graph above) was the variable that the subjects were normalized on. That is, at the beginning of the study, the averaged Positive Fusional Vergence was the same for all three groups. At the end the office-based group had moved up to the normal range whereas the pencil-push-up group actually underperformed the placebo group. This is pretty convincing evidence that vision therapy accomplishes what pencil push-ups do not.

Update: The above study was a precursor to a larger study that was finally reported in 2008 in the same journal. This new study covered 218 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. And this was a "gold standard" study where cause and effect could be legitimately determined.

Conclusion

If your child does poorly on the questionnaire discussed above (or on the Vision Assessment Checklist on this site) and struggles with reading, you need to 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 will not be getting the help needed to correct the problem.

Meanwhile all of the subsidiary effects of an undiagnosed or untreated vision problem will continue to emerge, including ADD-like behaviors, dyslexia and other learning difficulties. This is not to say that all of these are due exclusively to vision problems, but in some cases addressing the vision problem can make a huge difference in these other areas as well. At a minimum, your child becomes easier to teach or, putting it another way, more willing to learn.

The next topic, Why Such a Secret, explains why it is so difficult for many families to learn of these vision issues.