Instead of asking patients to stop rubbing their eyes, tackle the issue of the itch by determining whether its resulting from a heightened sensation or compensatory behavior or perhaps is a symptom of an ocular disease. Then, offer them solutions to improve their comfort, such as cooled, preservative-free artificial tears, this study suggests. Photo: Getty Images.

Numerous studies have confirmed an association between keratoconus and eye rubbing, though it remains unclear which comes first—the chicken or the egg? Early keratoconus could promote eye rubbing, but it’s also possible that an instinct to rub eyes may contribute to keratoconus. Even if we don’t know exactly how, we know the two variables are connected.

For individuals with psychiatric disorders who experience heightened sensory responses, the urge to itch may be stronger or harder to control, causing them to rub their eyes more frequently. It doesn’t help that the cornea is one of the most sensitive sensory structures in the body. Therefore, to see if an association exists, researchers recently examined the prevalence of keratoconus among patients with psychiatric disorders including anxiety, obsessive-compulsive disorder (OCD), autism and attention-deficit/hyperactivity disorder (ADHD). They found that only the latter was associated with keratoconus, and only in males.¹

The large study included 940,763 adolescents and adults were included (mean age: 17.6 years; 59.3% male). Of these, 1,533 had a diagnosis of keratoconus, amounting to a prevalence of 0.16%. Psychiatric comorbidities were documented in 107,249 or 11.4% of patients: 0.5% for anxiety disorders, 0.1% for OCD, 0.1% for autism and 10.6% for ADHD.

The researchers found that compared with the general population, patients with keratoconus were more likely to be diagnosed with ADHD (odds ratio: 1.58), even after adjusting for possible cofounders. When they stratified the cohort based on age, it revealed an association between keratoconus and ADHD for males (OR: 1.62), but not for females (OR: 1.29). In their paper on the study, published in JAMA Ophthalmology, the researchers explained that “Sex is known to be associated with clinical findings in patients with ADHD, with females exhibiting fewer internalizing behaviors (a range of self-harming activities as a reaction to stress or negative emotions).” If going along with the theory that the common thread between keratoconus and ADHD is eye rubbing, this could explain why the condition was only associated with keratoconus in male patients.

The lack of an observed association between keratoconus and the other psychiatric disorders evaluated in this study—OCD, autism and anxiety—was not addressed in the authors’ paper, an invited commentary pointed out.² The piece, titled “Do Not Think of a Purple Wolf—Keratoconus, ADHD, and Itch,” presented the possibility that “perhaps the lack of association was due to the lower sample sizes, with two, four and 10 participants with keratoconus in those groups, respectively, and wide confidence intervals.”²

Another interesting finding of the study that the commentary responded to was that the severity of keratoconus and the severity of ADHD weren’t found to be associated. “If there is another underlying mechanism to link ADHD and keratoconus outside of the heightened sensation of itching and eye rubbing, it is not obvious,” its authors wrote.²

When summarizing the study’s conclusions, the researchers wrote, “Although a causative effect could not be ascribed, these findings support further investigation into the potential value of education regarding eye rubbing in this population.”¹ In rebuttal, the commentary authors presented a metaphor to illustrate how this suggestion might have the opposite effect on the behavior:

“Do not think of a purple wolf. Did you think of a purple wolf? Of course you did. Just like you think of a purple wolf, a person with itchy keratoconic eyes reflexively rubs their eyes. You can train yourself to not think or not do these things, but the urge to rub your eyes when they itch is intrinsic.”²

Telling your patients to stop rubbing their eyes is unrealistic, which is why the commentary authors advise physicians to focus instead on the itch itself. They suggest trying to find answers to questions like “Is the itch from a heightened sensation or a compensatory behavior for something else?” and “What relief does rubbing provide?” Because it is your job as an eyecare provider to help minimize patients’ symptoms and discomfort, you can recommend cooled, preservative-free artificial tears, or medication or surgical treatment (crosslinking or keratoplasty) in more severe cases, they added.

While this study offered a bit of clarity, there remains many unanswered questions about the associations between keratoconus, ADHD/other psychiatric disorders and eye rubbing. Future research should evaluate risk factors for keratoconus and include specific documentation on eye rubbing habits, the researchers suggest.