![]() See also separate Examination of the Eye article. There is a secondary sympathetic effect modulated by adrenergic receptors in the Edinger-Westphal nucleus which are inhibited by the direct action of sympathetic amines. The sympathetic fibres then travel with the trigeminal nerve through the superior orbital fissure to the ciliary muscle. Postsynaptic neurons travel down all the way through the brain stem on each side and finally exit through the cervical sympathetic chain, travel over the lung apices, and ascend to the superior cervical ganglia with the carotid artery, then onwards as a plexus around the internal carotid artery, passing through the cavernous sinus. The sympathetic input then comes from the hypothalamus with the first synapse at the ciliospinal centre at C8-T1 level. ![]() During sleep the pupils are partially constricted but still react to light. The pathway begins in the cortex, which exerts a modulatory effect on constriction which is lost during drowsiness and sleep but increased during intense concentration and arousal. Pupillary dilatation is controlled by the sympathetic system and is efferent only. Short ciliary nerves then innervate the iris sphincter and muscles of accommodation. They travel in the superficial part of the oculomotor nerve via the cavernous sinus and the superior orbital fissure to synapse in the ciliary ganglia. From each Edinger-Westphal nucleus, preganglionic parasympathetic fibres exit with the oculomotor nerve. Each pretectal nucleus has two pupillary motor outputs, one to the Edinger-Westphal nucleus on its own side and one to the other side. The efferent limb for pupillary constriction comes from the pretectal nucleus via the Edinger-Westphal nucleus (also in the midbrain) to the ciliary sphincter muscle of the iris. The afferent limb is made up of the retina, the optic nerve and the pretectal nucleus in the midbrain, all on the same side. However, if you have the symptoms of Horner syndrome described above, or if your pupils change size suddenly throughout your adult life, it is highly recommended to seek medical attention as soon as possible.The pathway for pupillary constriction for each eye has an afferent limb taking sensory information to the midbrain, and two efferent limbs (one to each eye). For many people who do experience differentiated pupils, it is not a new condition and tends to be present from birth. While most of the time having unequal sized pupils results in little or no damage to one’s vision, for others the impact of differentiated pupils can be life-changing. When to consult your local independent optician This depends on the type of drug you have taken but in all cases our pupils resume to their regular size once the effects of the drug have worn off. Our pupils commonly increase in size when we are under the influence of recreational drugs which send stimulating signals to our nerves which can either increase or decrease the size of our pupils. If you are experiencing any of these symptoms then you should get medical attention immediately. This syndrome typically results in a reduced pupil size in one eye and is joined by a series of other symptoms such as droopy eyelid and decreased sweating in the impacted side of your face and eye. This syndrome is the outcome of a disruption of nerves between the brain towards the face and eye on one side of the body only. If you are experiencing a reduced pupil size on one side of your face it might be an indication that you are suffering from Horner syndrome. However, if you also experience additional symptoms, such as drooping eyelids or fever, you ought to seek medical attention as soon as possible. For some people who have anisocoria, there is no impact upon one’s sight, which is termed physiologic anisocoria. This condition means that your pupils will not necessarily be identical. If you happen to notice that your pupils are dilating to different extents at the same time it might be that you have an eye condition called anisocoria. Here are some of the main reasons for why your pupils are different sizes. This is particularly common when other symptoms are present as well. Normally our pupils tend to be identical in terms of when and how much they dilate, but for some people, a differentiated pupil size can be indicative of an underlying health problem. Most of us probably don’t spend much time looking at the shape or size of our pupils.
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