Tracking postoperative head positioning in endothelial keratoplasty using a head positioning sensor
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LETTER TO THE EDITOR
Tracking postoperative head positioning in endothelial keratoplasty using a head positioning sensor Elizabeth Shen 1
&
Frank Brodie 2 & Sahil Aggarwal 3 & Sanjay Kedhar 1
Received: 26 January 2020 / Revised: 5 May 2020 / Accepted: 8 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Dear Editor, Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK) have become standard posterior corneal replacement techniques due to excellent visual outcomes and faster visual rehabilitation compared with traditional full-thickness transplants [1–3]. Graft adherence is achieved by injecting an air or gas bubble into the anterior chamber. However, graft detachments remain the most common complication of endothelial keratoplasties (EK) [3, 4]. Postoperative head positioning has been thought to help prevent graft dislocations by maximizing the tamponade effect of the air or gas bubble on the graft. However, patient adherence to positioning has not been well-studied. We assessed patient adherence to supine positioning after EK using a head positioning sensor. Patients undergoing either DMEK or DSAEK at Gavin Herbert Eye Institute, University of California, Irvine between December 2017 and May 2018 were included. This study was approved by the institution’s Institutional Review Board. The head positioning sensor uses the MetaWear C sensor board (MbientLab, San Francisco, CA) (Fig. 1a), which comprises a 3-axis accelerometer and gyroscope. The device is Bluetooth-enabled such that it connects to an iPhone (Apple, Cupertino, CA) via the MetaWear iOS application interface. The sensor is attached to an adjustable headband that is fitted around a patient’s head (Fig. 1b). The iOS application records head angle data in spherical angle coordinates and records a * Elizabeth Shen [email protected] 1
Department of Ophthalmology, Gavin Herbert Eye Institute, University of California, Irvine, 850 Health Sciences Rd., Irvine, CA 92697, USA
2
Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
3
School of Medicine, University of California, Irvine, Irvine, CA, USA
binary output of whether the head angle is in the correct position. This device was previously validated in a pilot study of healthy volunteers [5, 6]. A net deviation > 45° from the calibrated reference point in any axis or combination of axes was defined as being out of position for this report. This threshold was determined by simulating postoperative positioning in a healthy subject. We used 20% SF 6 in DMEK and air in DSAEK. Postoperatively, patients were fitted with the device, which was then calibrated to set the supine head position as the reference point. The MetaWear iOS application collected data every 30 s for up to 24 h. Patients were instructed to wear the headband continuously until their postoperative day one visit and were given an iPod with the MetaWear iOS application. At the postoperative visit, the device was returned and
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