There is no apparent perfusion of the iris vessels with fluorescein in humans when the intraocular pressure is elevated above the diastolic ophthalmic artery pressure. Further mydriasis also occurs with increasing intraocular pressures above the diastolic ophthalmic artery pressure when the duration of pressurization is held constant. Iris ischemia alone cannot explain satisfactorily the mydriasis associated with increased intraocular pressure.
Rutkowski PC, Thompson HS. Mydriasis and Increased Intraocular PressureII. Iris Fluorescein Studies. Arch Ophthalmol. 1972;87(1):25-29. doi:10.1001/archopht.1972.01000020027005