Comparison of intraoperative intraocular pressure using different head fixation devices in prone spinal surgery

Study objective

We aimed to compare intraoperative intraocular pressure (IOP) during prone spinal surgery using a horseshoe headrest versus pinned head-holder to identify the safer device, which causes a lower increase in IOP.

Design

A prospective cohort study.

Setting

Operating room.

Patients

Healthy adults (aged 49–78 years) with an American Society of Anesthesiologists classification of I/II.

Interventions

Prone spinal surgery using a horseshoe headrest (Hs group) or pinned head-holder (Pin group) during 2016–2018.

Measurements

Both groups were examined for IOP, anterior chamber angle, and fundus findings the day before surgery. The IOP was measured immediately after intubation until the end of surgery. Risk factors for increased IOP in prone positioning were examined. A linear mixed model was used to investigate the rate of IOP increase with operative time.

Main results

The IOP in both groups was similar after 1 h and 2 h in the prone position and was highest at suture closure. The range of significantly elevated IOP varied in each group. The Pin group took longer to elevate IOP after prone positioning and recover IOP after supine positioning than the Hs group. The operative time and prone duration were significantly greater in the Pin group, with no significant IOP difference between the groups at all time points. The linear mixed model showed a high rate of IOP elevation up to 1 h in the prone position, after which the rate of IOP elevation decreased, with no significant IOP difference between the two groups at any time point. No risk factors for increasing IOP in the prone position were identified.

Conclusions

No differences in intraoperative IOP according to the head fixation device were observed. Therefore, the incidence of postoperative visual impairment could be comparable between the devices if direct eye compression is avoided during surgery.