Were you aware that variable pupil sizes amongst people affect up to one in five?
We are not talking a massively recognizable difference but the diameter of the pupil can have a variant of less than 0.5 mm, up to 1 mm (0.05 inch). Many babies are born with different sized pupils but this does not provide an indicator of underlying vision problems. It is feasible that other family members are also diagnosed with Aniscoria ( the term for differing sized pupils) which would make it a possible genetic condition.
It is possible to have a temporary differing size pupil which returns to normal for many underlying unknown reasons and is nothing whatsoever to worry about. However, unequal pupil sizes measuring more than 1 mm that develops later in life and then doesn't return to equal size may be indicative of another problem, such as a brain,eye, blood vessel, or nerve disease disorder. Common causes for pupil size differentiation are the use of eye drops. Asthma inhalers in particular can trigger a change.
More serious causes can include and are not limited to bleeding caused by head injury inside the skull, an abscess or brain tumor, an aneurysm, glaucoma and the increased pressure brought on by the condition within the eye, migraine headaches or a seizure or any kind of increased intracranial pressure.
Any sudden change should be reviewed by a medical professional. A new development of different sized pupils may be a sign of a very serious condition.