April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Short-term IOP Spikes Constitute Over 11% of the IOP Energy the Eye Must Absorb During Waking Hours
Author Affiliations & Notes
  • J Crawford C Downs
    Ophthalmology, University of Alabama at Birmingham School of Medicine, Birmingham, AL
  • Lisa Hethcox
    Ophthalmology, University of Alabama at Birmingham School of Medicine, Birmingham, AL
  • Kevin J Byrne
    Ophthalmology, University of Alabama at Birmingham School of Medicine, Birmingham, AL
  • Vincent Libertiaux
    Ophthalmology, University of Alabama at Birmingham School of Medicine, Birmingham, AL
  • Christopher A Girkin
    Ophthalmology, University of Alabama at Birmingham School of Medicine, Birmingham, AL
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 1664. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      J Crawford C Downs, Lisa Hethcox, Kevin J Byrne, Vincent Libertiaux, Christopher A Girkin; Short-term IOP Spikes Constitute Over 11% of the IOP Energy the Eye Must Absorb During Waking Hours. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1664.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract
 
Purpose
 

To quantify the contribution of short-term IOP spikes to overall IOP energy using continuous, bilateral IOP telemetry.

 
Methods
 

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 for twelve 24-hour periods in a 14-day span in 3 young adult male rhesus macaques (NHP) aged 3-6 years old. The IOP transducers were calibrated directly via anterior chamber manometry, and IOP data were corrected for signal drift. IOP fluctuations >1 mmHg over baseline and lasting <~2 seconds were characterized. The number of IOP spikes, and the percentage of IOP energy due to IOP spikes as a percentage of the total IOP energy were calculated for each hour.

 
Results
 

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. IOP spike energy varied widely between NHPs, but was significantly higher during waking hours in all three NHPs. Overall, IOP spikes accounted for 11% of the total IOP energy that the eye must absorb during waking hours. In all three NHPs, over 10,000 IOP spikes per hour >2 mmHg hit the eye during the day, which decreased to <4,000/hr. at night.

 
Conclusions
 

The eye is exposed to over 10,000 short-term IOP spikes per hour during the day, which represents a significant but previously uncharacterized part of IOP energy. This constitutes up to 16% of the total IOP exposure the eye must absorb. 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.

 
 
(Top) A screenshot of 12 seconds of bilateral IOP telemetry data showing the dynamic nature of IOP. (Middle) IOP spikes are detected, counted, and their energy calculated (orange areas) relative to baseline IOP (2 seconds of data shown). (Bottom) Mean hourly IOP spike energy as a percentage of total hourly IOP energy plotted as hourly means from midnight to midnight, averaged over all twelve 24-hour recording periods for each eye in 3 NHPs. Time is plotted on the 24-hour scale; waking hours are hours 7-18, and lights-out are hours 1-6 and 19-24.
 
(Top) A screenshot of 12 seconds of bilateral IOP telemetry data showing the dynamic nature of IOP. (Middle) IOP spikes are detected, counted, and their energy calculated (orange areas) relative to baseline IOP (2 seconds of data shown). (Bottom) Mean hourly IOP spike energy as a percentage of total hourly IOP energy plotted as hourly means from midnight to midnight, averaged over all twelve 24-hour recording periods for each eye in 3 NHPs. Time is plotted on the 24-hour scale; waking hours are hours 7-18, and lights-out are hours 1-6 and 19-24.
 
Keywords: 568 intraocular pressure  
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×