Tuesday, December 11, 2007

4.6 Huge pupils

The size of the pupil does change with age, from somewhat small in infants to 3-5 mm in adults, then it becomes smaller again in older people. It is a change in the muscle tone of the iris sphincter and dilator. In a dilated eye exam, eyedrops are used to paralyze the sphincter and stimulate the dilator to maximize pupil size.

Sometimes we see unusually large pupils in children. These are cause by medication, i.e., medicine-induced mydriasis (about 8mm pupil size). Seen in children treated for ADHD, for example.

According to a 2003 CDC report, 4.4 million kids between 4-17 years old have been diagnosed with ADHD, and 2.5 million of them received medical treatment. The commonly prescribed medications, Adderall (an amphetamine) and Strattera (a norepinephrine re-uptake inhibitor), all have a long list of side-effects. And among them, mydriasis - from a sympathomimetic effect causing contraction of the iris dilator muscle. As a result, the angle narrows which may cause or acerbate narrow-angle glaucoma. In severe cases, the patients suffer from debilitating headaches and photophobia.

2.5 million is not a small number, that is probably why some of these kids show up for eye exams because of blurred vision and reading difficulties due to decreased accommodation. So the scholastic performance may suffer albeit with improving behavior. A paradox of sorts. Unfortunately, there is currently no effective management for this problem.

As they say: more studies are needed.

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