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Anna Edmiston, Daniel C Turner, Lisa A Hethcox, Christopher A Girkin, J Crawford C Downs; The Magnitude of IOP Spikes Associated with Blink and Saccade. Invest. Ophthalmol. Vis. Sci. 2014;55(13):149.
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To determine the magnitude of IOP spikes associated with blink and saccade.
We have developed and validated an implantable telemetry system that wirelessly records 500 measurements of IOP per second for up to 2-1/2 years (IOVS 52(10):7365-75). Using an enhanced version of this system, continuous bilateral IOP, bilateral electro-oculogram (EOG), and aortic blood pressure were recorded in 3 young adult male rhesus macaques (NHP) aged 3-6 years old while watching a video of playing macaques. Eye movements and blinks were monitored using high-definition video of the animals’ faces recorded at 60 frames/s, which was synced to the IOP telemetry data to 33 ms precision. The IOP transducers were calibrated directly via anterior chamber manometry, and IOP data were corrected for signal drift. For each animal, the magnitude of IOP spikes associated with blinks and saccades seen in the video were calculated and reported relative to baseline IOP.
As seen in the Figure, IOP is incredibly dynamic, with blinks, saccades and other external forces generating short-term IOP spikes of significant magnitude over baseline. Blinks generated IOP spikes ranging from 4.9 to 14.9 mmHg over baseline IOP, with an overall average of 8.9 mmHg above baseline. Saccades generated IOP spikes ranging from 2.0 to 13.4 mmHg over baseline IOP, with an overall average of 7.0 mmHg above baseline. Blinks and saccades generated very similar IOP spikes in contralateral eyes, and vertical and horizontal saccades generated IOP spikes of similar magnitude.
IOP is incredibly dynamic. Blinks and saccades generate large, short-term IOP spikes in NHPs. The eye is exposed to many IOP spikes throughout the day, which represents a significant but previously uncharacterized part of IOP energy. The dynamic nature of these spikes represents a different biomechanical insult than longer-term IOP fluctuations, and may be important in IOP-related diseases such as glaucoma.
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