OnTrack Reading

I’m not a vision expert by any means, but I’ve done a fair amount of reading on the sort of vision problems that can cause a child to struggle with reading and one of the big ones involves poor convergence ability or convergence insufficiency.

The Skill of Convergence

The ability to converge your eyes is a skill that develops in childhood. A baby can’t do it, but by age 2 or 3, most children can. What is it? It’s just the ability to bring both eyes together on a single point and hold them there. Ordinarily, when you relax the muscles in your eyes, you end up focusing at a distance. It takes muscle activity to pull your eyes together so that you can converge on a nearer point. Obviously, reading requires this skill, since most reading is done at a relatively close distance.

Some children fail to adequately develop this skill, or they fail to develop it at all. If they can’t converge to a nearpoint, they will end up seeing double or will be under considerable visual stress. If they can converge to a nearpoint, but they can’t sustain the effort for long, they might start out reading just fine, then gradually start falling apart, making more and more mistakes until they get a chance to take a short break.

Developmental optometrists are trained to assess convergence problems and recommend treatment. Sometimes the treatment can be as simple as a set of glasses with an appropriate prism in the lenses, but in my experience the treatment usually ends up being vision therapy.

Normal Development of Convergence Skill

Some of the literature on convergence problems indicates that convergence skills are developed during the crawling phase of childhood when a child is required to focus on his hands to see where he is placing them.

Similarly, it’s said that the old “monkey bars” built convergence skill because with poor convergence, depth perception is lacking and with poor depth perception, a child will miss the next bar. This is also true of the suspended horizontal ladder seen on some playgrounds. Miss the next rung and you fall or dangle helplessly, so there’s an incentive to concentrate your visual efforts on a precise point.

Remember, though, that genetics comes into play in all of this. If your child skipped crawling and went right to walking, he might have done so because he was so visually uncomfortable trying to look at the floor in front of him that he struggled mightily to get to his feet where the view was easier on the eyes (because he didn’t need to converge his eyes to see it.)

Similarly, if your child wasn’t inclined to take some risks on the playground, that might have been due to his falling several times on early attempts and deciding against continuing. In other words, crawling, monkey bars and horizontal bars very likely do help develop convergence skills in normally developing children, but if your child was at a genetic disadvantage in that regard, he might have made a conscious, or subconscious, decision to avoid those activities altogether. Had he stayed with them, suffering the discomfort and possible embarrassment due to constant failure, he might have then developed his eyes’ ability to converge appropriately, or maybe not.

One of the huge benefits of school programs that direct young children through such activities in an organized manner is that children, by progressing with constant practice, come to understand that such play is something they need and will benefit from, rather than something to avoid. Of crucial importance, though, is that the professional educators working with these young students also understand that they are directing more than just playtime, and that the benefits are long lasting, and probably more beneficial to a five-year-old than being taught to read, especially to those five-year-olds who haven’t yet developed the convergence ability required to do close-up work comfortably.

The Brain’s Workaround

As I’ve said elsewhere on this site, vision problems usually run in families. And, due to the relative scarcity of developmental optometrists, most adults who had vision problems as children have never had them addressed, though they might eventually have overcome them.

Interestingly, if you tested those adults today you would probably find that many of them didn’t end up with good convergence skills, but instead developed compensating mechanisms. One of these mechanisms is to have gone to using only one eye when reading, so that the brain isn’t confused by two conflicting images. I had a parent in my office one day whose child I was certain had an untreated vision problem and I was trying to demonstrate something to this parent. When he put on a pair of polarized glasses, instead of seeing what he was supposed to see, he said that one side of the target was completely black. Without going into detail, that is what would logically happen if he was only using one eye for nearpoint work.

However, he had both eyes open, so what was happening? Well, it turns out that the brain is inventive when presented with a problem like poor convergence skill. First, it tries to solve the problem rationally, by getting both eyes into the game. It does this in a fascinating way, and in a way that can be observed using red/green glasses commonly seen in vision therapy centers. When you put a red lens in front of one eye and a green lens in front of the other, then try to read print through a plastic sheet with alternating red and green transparent striping, the print going through a red stripe can only be seen by the eye behind the red lens because red and green cancel out, resulting in a black stripe. In other words, if you closed the eye behind the green lens, you would see alternating red and black stripes because the green plastic stripe would appear black.

Using these red/green glasses, it is easy to spot a child (or an adult) who is suppressing the visual input from one eye. In the adult’s case, that suppression is very likely permanent and affects the same eye constantly. However, in the case of a young child, vision therapists often observe a phenomenon called alternating suppression, which I believe is caused by the brain attempting to first train normal convergence ability before taking the drastic route of shutting down the input from one eye when doing nearpoint work.

Next: Alternating Suppression, or return to the OnTrack Reading Home Page