Neck Ties and IOP

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Normal intraocular pressures (IOP) range between 10 mm Hg and 22 mm Hg.  Wearing a neck tie can cause increases in IOP of 2 mm Hg to 4 mm Hg.  The putative mechanism of IOP increase involves compression of the jugular veins by the neck tie, leading to increased hydrostatic intravascular pressure transmitting upstream to the episcleral veins around the eye.  Episcleral veins, in turn, are directly involved in establishing IOP.
 Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1771792/