Often, during the ophthalmological visit, it is necessary to dilate the pupils with eye drops in order to carry out a complete and detailed examination of the retina and other elements inside the eye that cannot be seen without mydriasis. Some medicines, both by general route and by topical route (eye drops).Third cranial nerve palsy (oculomotor nerve that runs from the brain to the eye and controls the position of the eyelid, the movement of the eyeball and the size of the pupil): in these cases, pupillary dilation is usually associated with ptosis (droopy eyelid), double vision and/or visibly misaligned eyes.Eye diseases or injuries in which the iris can be damaged: eye trauma, inflammation of the iris (iritis or uveitis), glaucoma, etc.Neurological diseases: migraine, cerebrovascular accident or stroke, brain haemorrhage, tumours or infections.There are different causes for mydriasis to occur. Sometimes the pupils dilate without changes in lighting and are larger than usual the medical term for it is mydriasis. The pupil works thanks to two muscles: the sphincter of the pupil, which closes it, and the dilator muscle of the pupil, which opens it.
The pupils change size depending on the lighting, measuring from 2 to 4 mm in bright light and from 4 to 8 mm in low light or darkness to increase the amount of light the eyeball receives, and also influence the ability to eye focus. The pupil is the black hole located in the centre of the iris, the part that gives colour to the eye.
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