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David A. Maerker, Nadezhda Cvetkova, Horst Helbig, Philipp M Prahs; Continuous Head Tracking After Intraocular Surgery Under General Anesthesia. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4484.
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© ARVO (1962-2015); The Authors (2016-present)
Resorption of remaining subretinal fluid occurs rapidly after vitrectomy with intraocular gas in retinal detachment surgery. Head orientation (HO) in that period can affect the formation of arcoid retinal folds. Reliable methods to monitor the patients posture are not commonly available. We used an Inertial Measurement Unit (IMU) to describe the HO over time of patients after intraocular surgery under general anesthesia (GA) without posturing instructions aiming to objectify posturing recommendations.
Five subjects were enrolled in the study that required intraocular surgery for various conditions under GA. An IMU (InvenSense MPU6050) was coupled with a microcontroller and a data recorder. The device was fixated on the hard eye shields that were applied directly after surgery. HO was continuously recorded during the first six hours after surgery for all subjects with a frequency of 5 Hz. Quaternion sensor output from the IMU was converted to the direction of gravity in the subject frame and categorized to the following states for each datapoint: standing (ST), prone (PR), suppine (SU), lying left (LE), lying right (RI) and upside down (UD). The category was accepted when gravity vector direction did not differ from the corresponding prinicipal direction more than 30 degrees. Otherwise the datapoint was categorized as one of the intermediate states LE/ST, RI/ST, PR/ST, SU/ST, LE/PR, LE/SU, RI/PR, RI/SU. Descriptive statistics of HO states for the first 90 minutes after regaining consciousness and for the remaining 270 minutes were calculated.
During the early interval predominant states averaged over all subjects were the suppine SU and SU/ST states accounting for 66.5% of that interval. Pure side states (RI and LE) and intermediate side states were registered in only 4.2% and 12.4%, respectively. For the late interval SU and SU/ST states decreased to 30.9% while the upright ST state increased from 9.8% to 34.4%. Pure side states and intermediate side states remained uncommon with 4.8% and 18.5%, respectively. Prone states were rare with 2.6% and 2.8% of the early and late interval, respectively.
IMUs are effective in monitoring HO after intraocular surgery. Our data suggests that posturing recommendations are advisable for cases intended to stay lying in side or prone positions. Further investigations to correlate surgical outcomes to postoperative posture data are desireable.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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