Changes in optic nerve sheath diameter and intraocular pressure as a surrogative marker of postoperative visual loss in patients undergoing surgery in prone position– Prospective observational study

• Author Details:   
• Vinothkumar Appukuttan ^*
• Kumaresan Sathappan
• Arun Sekar Gnanasekaran
• M J Venkatesan
• K Sumedha

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Background: Postoperative visual loss is a devastating complication that can occur following prone surgery. One of the significant causes of postoperative visual loss is ischemic optic neuropathy. This study aimed to investigate the effects of the prone position on intraocular pressure (IOP) and optic nerve sheath diameter (ONSD), which could serve as potential markers for postoperative visual loss.

Materials and Methods: Forty-seven patients who met the inclusion criteria were included in the study, and their intraocular pressure (IOP) and optic nerve sheath diameter (ONSD) were measured at five different time points: T0 (awake patient in the supine position), T1 (ten minutes after induction of general anesthesia in the supine position), T2 (ten minutes after assuming the prone position during surgery), T3 (at the end of surgery in the prone position), and T4 (ten minutes before extubation after repositioning to the supine position). The data collected were analysed using one-sample t-tests and linear regression analysis to assess the variations in IOP and ONSD.

Results: The study included 22 male participants (46.8%) and 25 female participants (53.2%), with a mean age of 44.2 ± 9.7 years. The total duration of prone positioning during surgery was 152 ± 27 minutes. Both IOP and ONSD were found to be significantly higher in the prone position at T3 compared to the supine position at T1 (p = 0.00). Additionally, a positive linear correlation was observed between the duration of prone positioning and the increase in IOP, with an r-value of 0.386.

Conclusions: Prone positioning during surgery is associated with significant increases in both intraocular pressure and optic nerve sheath diameter, which may contribute to the risk of postoperative visual loss. Preventive measures should be implemented to monitor and manage these factors during prone surgeries to reduce the risk of postoperative visual loss.

Keywords: Intraocular pressure, Optic nerve sheath diameter, Postoperative visual loss.