In six human volunteers, serial electroretinograms (ERGs) were performed over five minutes at intraocular pressure artificially elevated with a suction cup. Compared to the base line ERG, there was no decrease in b-wave amplitude unless intraocular pressures approached or exceeded diastolic ophthalmic artery pressure, as determined by suction cup ophthalmodynamometry. Although reduced severely, the b-wave was not completely obliterated within five minutes, even at intraocular pressures above the mean ophthalmic artery pressure and in some cases above systolic artery pressure.