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PurposeTo quantify the effect of negative pressure applied to the anterior surface of the eye on absolute IOP.SubjectsParticipants, and/or Controls. Three eyes from three research-consented brain-dead organ donors.MethodsAir-tight goggles connected to a negative pressure (NP) pump (Mercury Multi-pressure Dial (MPD); Equinox Ophthalmic, Inc., CA) were tested on three research consented brain-dead organ donors. The MPD was set to generate a vacuum of −20mmHg. A baseline IOP of 10, 20, and 30mmHg was sequentially set by adjusting the height of a balanced salt solution bottle connected to the cornea through a 20G needle. IOP was manually annotated at time = 0s, right before turning on the vacuum pump; after a few seconds with the vacuum pump ON; at 60s; at 120s, right before turning the pump OFF; at 240s with the pump OFF (recovery). Three repetitions per each test at varying baseline IOP were taken for a total of nine series of measures per eye.Main Outcome MeasuresIOP change with exposure to NP.ResultsEye1 and 3 showed an immediate reduction in IOP at all baselines immediately following activation of the MPD NP pump; Eye2 showed an opposite response to NP. Eye1 and 3 showed a reduction in IOP at all baselines with NP pump ON for 60s and 120s, while Eye 2 showed a consistent increase in IOP. After 120s from turning NP OFF (time=240s), IOP partially recovered to its baseline in all eyes.ConclusionsThis study is the first to evaluate changes in manometrically-measured intracameral IOP due to NP applied to the ocular surface in living conditions. The inconsistent response of IOP following exposure to negative pressure warrants further investigations on the mechanism underlaying IOP lowering by NP.