IOP vs pressure level

IOP and pressure level both are nouns.

Word	Noun	Adjective	Verb	Adverb
IOP	Yes	No	No	No
pressure level	Yes	No	No	No

As nouns, pressure level is a hypernym of IOP; that is, pressure level is a word with a broader meaning than IOP:

IOP: pressure exerted by the fluids inside the eyeball; regulated by resistance to the outward flow of aqueous humor
pressure level: the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit)

Other hypernyms of IOP include force per unit area, pressure.

IOP (noun)	pressure level (noun)
pressure exerted by the fluids inside the eyeball; regulated by resistance to the outward flow of aqueous humor	the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit)