Eye disease frequently asked questions
Q. If your nose was blocked and you were to blow it really hard a few times to clear it, could the pressure have an effect on the eyes by causing a color change in the iris?
A. Straining and increasing the pressure inside the head or eye does not cause a change of iris colour or affect the pigment in the eye. It is possible to burst a blood vessel on the surface or even inside the eye by doing this so if your vision is affected, then you must get your eyes examined immediately.
There is a condition called pigment dispersion syndrome (PDS) where the eyes do shed pigment granules and there can be an effect on the colour of the iris. There is a link between the shedding of pigment in PDS and physical exertion (such as exercise) but there isn’t a known link between short term straining (eg blowing the nose) and this effect. In any case the actual effect on your iris colour will be very very minimal and probably not noticeable.
So the short answer to the question is ‘No you can’t affect the colour of the eyes by blowing your nose’.
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