To investigate the diameter, the infusion and aspiration rate of 20-, 23- and 25-gauge vitreous cutters, and compare the theoretical and practical intraocular pressure (IOP) change according to the height of the bottle.

A vitreous cutter was disassembled to measure the actual external and internal diameter. The infusion rate was measured at the height of 40, 60, 80, 100 and 120 cm and the suction rate was measured at a pressure of 100, 200, 300, 400 and 500 mm Hg for each gauge. IOP during the operation was calculated according to the bottle height and the actual IOP was measured using a mercury sphygmomanometer.

The external diameter of the 20-, 23- and 25-gauge was 900, 596, and 500 mm, respectively, and the internal diameter was 670, 450, and 380 mm, respectively. The infusion rate increased in direct proportion to the bottle height. The aspiration rate increased as the pressure increased. However, the increment of the infusion and aspiration rate in the 20-gauge vitreous cutter was the highest and decreased in the 23- and 25-gauge, in that order. IOP was calculated as 29, 44, 59 and 74 mm Hg when the bottle height was at 40, 60, 80 and 100 cm, respectively, and was measured 34, 50, 62 and 74 mm Hg, respectively.

The infusion and aspiration rates per outer diameter in the 23- and 25-gauge vitreous cutters and infusions using cannula were lower than in the 20-gauge vitreous cutter. The difference of the infusion and aspiration rates per diameter between the 23- and 25-gauge vitreous cutters and infusions was not significant.