CI treatment has strong outcome data behind it, which makes it worth asking directly why some patients don't get the results the research would predict. In my experience, it's rarely because vision therapy "doesn't work" — it's because something in the diagnostic picture or the treatment plan wasn't quite right to begin with.
Something Else Going On
When vision therapy for CI doesn't fully resolve, it's rarely because the therapy itself doesn't work — it's usually because something else in the patient's life or physiology is limiting how much benefit they can actually receive.
Neurological injury sets a real ceiling in some cases. A patient recovering from a stroke or a brain injury may improve substantially — genuinely getting most of the way there, say 78% better — without ever fully closing the remaining gap, simply because the underlying neurological system has a real limit to how much it can recuperate. That's still a meaningful outcome, even when the last portion doesn't resolve.
Direct injury to the muscles or nerves responsible for convergence is a less common but real limiting factor, and it changes what's actually achievable regardless of how well-executed the therapy is.
Psychosocial factors matter more than they get credit for. Undiagnosed anxiety, difficulty managing stress, or past trauma can genuinely block a patient from receiving the full benefit of treatment. Convergence is, in a real sense, the manifestation of taking on visual stress — asking the eyes to converge is asking the nervous system to accept a demand. A patient whose overall stress tolerance is already maxed out elsewhere in their life often can't accept that additional demand psychologically, even when the visual system itself is capable of it. I've seen patients with essentially no capacity to tolerate stress in their lives have a genuinely miserable time in vision therapy for exactly this reason — the system is already overloaded, and it simply won't accept a new stress on top of it.
And sometimes it's simply the learning curve. Vision therapy for any binocular vision disorder ultimately requires a patient to learn voluntary control over their eyes — gaze alignment, shifting gaze position through motor fusion. Once someone figures out how to do it, it tends to become relatively easy. But it has to be learned first, and learning requires practice. Very, very few people get it on the first go-round, and mistaking a normal early learning curve for a failed treatment is its own common error.
Compliance Gaps
Home reinforcement is half of what makes the CITT protocol work, and it's the half that's hardest to control. A patient who attends every office session but skips most of the home exercises is, functionally, undergoing a different and less effective treatment than the one the research validated. This shows up most often in older children and teenagers managing their own homework, where the daily habit is easy to let slide.
Severity and Timeline Mismatch
Some presentations are simply more severe than a standard course accounts for — a significantly receded NPC with minimal fusional reserve may need a longer or more intensive protocol than the typical structure assumes. When progress stalls partway through a standard course, extending the timeline or increasing session intensity is often the right adjustment, rather than concluding the approach itself has failed.
When the Diagnosis Itself Needs a Second Look
Occasionally, what looked like CI at intake turns out to be something else once treatment doesn't progress as expected — a mild, well-compensated finding that wasn't actually driving the patient's symptoms, with the real cause sitting elsewhere entirely. Lack of progress after a genuine, well-executed course of therapy is itself diagnostic information, and it's worth revisiting the original workup rather than assuming the treatment simply underperformed.