Intraocular pressure during lumbar disc surgery - a comparative study between prone position and knee-elbow position

ABSTRACT

Post-operative visual loss occurs more commonly in spinal surgery. Increased intra-ocular pressure is often Implicated In the etiology of postoperative visual impairment. We Investigated intraocular pressure in 20 patients undergoing lumber disc surgery. We classified the patients into two groups Group I patients were in the knee-elbow position with the head resting on a cushion and turned to one side and group II patients were in prone position and the head neutral. We classified patients in knee-elbow position into two sub-groups subgroup A where we measured IOP in nondependant eye and subgroup B where we measured IOP in dependant eye. In both groups we measured lOP during 2 times, the first time in both group when the patients were awake and In supine position and the second time was In group I at the end of surgery when the patients were still anesthetized and in knee elbow position and in group II at the end of surgery when the patients were still anesthetized and in prone position. In group I after mean duration of surgery 120 +/- 18 min. [mean +/- SD], the mean intra-ocular pressure in the non-dependnnt eye was unchanged when compared to awake state 16.3 +/- 2.1 vs. 17.2 +/- 3.2 mmHg [p >/= 0.05]. whereas the intraocular pressure in the dependant eye had significantly increased 17.1 +/- 2.2 vs. 19.2 +/- 1.1 mmHg [p<0.05]. In group II after mean duration of surgery 119 +19 mmHg, mean Intra-ocular pressure had highly significant increase compared to awake state 16.7 +/- 2.2 vs. 21.3 +/- 2.1 mmHg [p<0.01]. We conclude that IOP increased when anesthetized - patients are placed in prone position more than when placed in knee-elbow position