![]() Other illness-based causes include cluster headaches result in a drooping of the upper eyelid, and inter-cranial bleeding in the upper brain stem.Horner’s Syndrome is a combination of symptoms, including pupil miosis, resulting from nerve damage.Pupil contraction can result from certain diseases. Other drugs associated with miosis are nicotine, eye drops and nasal sprays, and some drugs used in cancer chemotherapy. The contraction of a pupil is called ‘miosis’. On the other hand, opiates like heroin, morphine, fentanyl and codeine have the opposite effect, as they are depressors rather than stimulants.Īs a result, they cause the pupil to contract. This results in a forced stimulation, which is exhibited by dilated, non-responsive pupils. Stimulant drugs like cocaine and amphetamines prevent the re-uptake of certain neurotransmitters, meaning that they remain active in the brain. This is due to increasing brain mass compressing the oculomotor nerve. Strokes, epilepsy and other nervous-system disorders often result in excessive dilation of the pupils. Some prescription medications contain substances that block certain chemicals being transmitted to the eyes, resulting in pupil dilation, as well as reduced sweating and dry mouth. What causes pupils to not react to light? ![]() But often, the cause may not be something as straight-forward as a head injury.Ĭauses of abnormal dilation can happen for numerous other reasons. Head trauma can damage the nerves of the pupil and iris, preventing contraction. A non-reactive – or fixed – dilated pupilĪ pupil which remains excessively dilated in the presence of light is known as a ‘mydriatic pupil’. But changes in the way the pupils respond to light can have a variety of causes.Įxcessive dilation – known as mydriasis – is a more commonly observed symptom, meaning constriction of the pupils – or miosis – has fewer underlying causes. Dilation and contraction of the pupils in light and dark environments is a natural response. ![]()
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