Intraocular pressure monitoring during prone percutaneous nephrolithotomy, should we pay attention?

Aims & objectives: Transitory post-operative visual loss in one of our patients following Percutaneus Nephrolithotomy (PCNL), led us to do a review the available literature on Post Operative Visual Loss (POVL) and to study the intraocular pressure (IOP) changes during prone PCNL. Introduction: POVL is a devastating complication in the setting of a non-ophthalmic surgery and can lead to severe legal consequences for the operating surgeon. Raised IOP leading to Ischaemic Optic Nerve Atrophy (ION) is one of the purported factor for POVL. Method: We serially measured IOP with a hand-held tonometer in 40 of our patients undergoing PCNL in prone position, at five-time point settings-Baseline; 10 minutes after anaesthesia (Supine 1); 10 minutes after putting the patient in prone position (Prone 1); At the end of the procedure (Prone 2); Before reversal of anaesthesia (Supine 2). Data analysis was done by repeated measures ANOVA and paired t tests using NCSS software. Results: Out of 40 patients 34(85%) were Males and 6 females (15%); with mean age of 46 years. The duration during which the patient was prone varied was 108.85 24.12 minutes. Measured IOP changed significantly in different positions, being highest in Prone 2 position. The rise in IOP had a linear relationship with the duration during which the patient was prone, reducing after anaesthesia reversal in supine position. Conclusions: Observing the safety measures in PCNL can go a long way in avoiding POVL, especially in those patients with large & complex stones necessitating the patient to be in prone position for longer durations.