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Convergence insufficiency often comorbid with ADHD
Insufficiency does not cause ADHD, but there is a threefold increase of it in patients with attention disorders.
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SAN DIEGO — Attention disorders and convergence insufficiency may be interrelated, and researchers are planning a prospective study to find out how.
Attention deficit hyperactivity disorder (ADHD) is considered to be one of the most common psychiatric disorders in children. Figures published in the American Journal of Public Health and reported by CNN stated that 6% of school-age children have been diagnosed with ADHD and that 90% of them receive Ritalin (methylphenidate, Novartis).
Other estimates vary between 4% and 12%, or 2.5 million children. The American Academy of Pediatrics issued new guidelines in May about assessing children.
Andrea Miller-Scholte, CO, COMT, of the Ratner Children’s Eye Institute in San Diego, said that ADHD occurred three times as often in children with convergence insufficiency over the incidence among the general population.
Ms. Miller-Scholte spoke about the “Relationship of Convergence Insufficiency and Attention Deficit Hyperactivity Disorder” at the American Association for Pediatric Ophthalmology and Strabismus meeting here.
“Despite the huge interest in it, there is still no specific diagnostic test for ADHD and the diagnosis remains a clinical one based on behavioral criteria,” she said. “The American Psychiatric Association’s DSM-IV criteria for ADHD includes such symptoms as: often avoids or strongly dislikes tasks such as homework that require sustained mental effort; fails to give close attention to details; often has difficulty sustaining attention in tasks; and often fails to finish schoolwork. Other references interestingly cite mildly dysmorphic features like hypertelorism.”
A diagnosis of ADHD has a huge impact not only on the life of the child, but also on the family, the school and society as a whole, Ms. Miller-Scholte said. Long-term medication and behavioral modification programs require a great amount of sacrifice by everyone involved in the child’s care and supervision, she added.
“It is imperative that a careful and thorough evaluation of the child be done before a definitive label of ADHD is applied,” she said.
Incidence
Part of the comprehensive evaluation for these children includes a general eye exam to rule out any underlying visual problems that may cause the child’s lack of concentration and poor academic performance at school, Ms. Miller-Scholte said.
“We observed, in our clinic, that quite a number of kids with, or suspected to have, ADHD also had convergence insufficiency,” she said.
The symptoms of convergence insufficiency include a poor ability to concentrate on near tasks, blurred vision and the sensation that letters and words run together, especially during prolonged periods of reading.
This led to the hypothesis that children with convergence insufficiency have a greater tendency to be diagnosed with ADHD than historical controls.
She conducted a retrospective chart review of all patients diagnosed with convergence insufficiency at the Ratner Children’s Eye Center at the University of California San Diego (UCSD) between 1994 and 1999.
She reviewed the charts of patients with a diagnosis of ADHD as reported by the family at the time of their initial visit or at any time during follow-up. Information regarding medications for ADHD within the period of diagnosis also were noted.
UCSD criteria for convergence insufficiency include a remote near point of convergence of greater than 6 cm from the tip of the nose; fusional amplitudes with a break at 16 PD or less; and a recovery at 6 PD or more from that break, or 50% of the break if that measurement was 20 D or more.
Exophoria was often present but not needed for inclusion in this study.
She found 266 patients with convergence insufficiency, and 26 (9.8%) had ADHD. Twenty-one were boys and five were girls. They had a mean age of 11.6 years, with a range from 6 to 51 years.
Twenty of the 26 ADHD patients (76.9%) were on medication when diagnosed with convergence insufficiency. Six patients (23.1%) were not medicated. Of those on medication, 85% were on a single drug and 15% were on multiple drugs. Of the 17 patients on single drug therapy, the majority was on stimulants.
Research expanded
Next, researchers reviewed the entire UCSD database to find all patients diagnosed with ADHD. Of the 1,705 patients, 176 were seen at the eye center and 28 (15.9%) were diagnosed with convergence insufficiency.
“We had triple the incidence of ADHD in our patients with convergence insufficiency as compared with ADHD in the general population in historical controls,” she said. “Additionally, we have found at least triple the incidence of convergence insufficiency in the ADHD population when compared with historical controls.”
Explanations include the possibility that convergence insufficiency is a comorbid disorder with ADHD and that ADHD medications could cause it. Reports exist describing drug side effects such as blurring and difficulties with accommodation.
ADHD also could cause convergence insufficiency, she said. Hypertelorism and its increase in the patient’s interpupillary distance could contribute to symptoms.
“Interestingly, we also recognize the loss of concentration that can cause a breakdown of an exophoria,” she said. “Does difficulty that the ADHD children have with concentration similarly cause convergence insufficiency?”
Finally, the presence of convergence insufficiency may cause a misdiagnosis of ADHD, especially in the non-academic setting where the overlap of ocular symptoms may confuse the non-ophthalmologist.
“The utilization of popularized checklists by teachers and parents untrained in their use has led to estimates as high as a 14% incidence by including problems that overlap but that are fundamentally different than ADHD,” she said. “Convergence insufficiency is clearly one such disorder.”
Researchers are planning a prospective, collaborative study with the UCSD Department of Pediatrics to look at these children before and after medication is prescribed. They also will examine whether treatment of convergence insufficiency alters the symptoms or diagnosis of ADHD.
“Understanding their connection may lead to identification of central nervous system fusional centers and pathways, as well as novel approaches to biochemical treatment of convergence insufficiency,” she said.
For Your Information:
- Andrea Miller-Scholte, CO, COMT, can be reached at the University of California San Diego/Ratner Children’s Eye Center, 9415 Campus Point Drive, La Jolla, CA 92093-0946; (858) 534-2020; fax: (858) 534-5695.
- The American Academy of Pediatrics’ recommendations are posted on the Web at www.aap.org/advocacy/releases/mayadhd.htm.