Hello and welcome to the Zero to Finals podcast.

My name is Tom, and in this episode I'm going to be talking to you about pupil disorders.

And if you want to follow along with written notes on this topic, as always, you can follow

along at zero definals.com slash pupil disorders or in the ophthalmology section of the zero definals medicine book.

So let's get straight into it. The pupil is formed by a hole in the center of the iris

and there's a number of conditions that can cause abnormally shaped or sized pupils.

First let's talk about pupil constriction and there are circular muscles in the iris

that cause the pupil constriction and they're stimulated by the parasympathetic nervous system

using acetylcholine as a neurotransmitter. The fibers of the parasympathetic nervous system

that innovate the eye travel along the ocular motor

or the third cranial nerve and into the pupil and the iris where they innovate those circular

muscles in the iris that cause pupil constriction. Next pupil dilation. The dilator muscles of the

pupil are arranged like spokes on a bicycle wheel

and they travel straight from the inside of the iris to the outside

and they're stimulated by the sympathetic nervous system

using adrenaline as a neurotransmitter.

So when these muscles contract, they pull the inside of the iris outwards and open the pupil up.

Next let's talk about abnormal pupil shapes.

And this can have a number of causes.

The first cause is trauma to the sphincter muscles in the iris, which can cause an irregular pupil.

And this could be caused by cataract surgery

or by other eye operations. A condition called anterior uveitis can cause adhesions which are scarred

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