Experimental closed system surgical procedures and intraocular pressure fluctuation.

PURPOSE To determine the behavior of intraocular pressure and its relationship with infusion pressure in vitrectomy, phacofragmentation and phacoemulsification surgeries in rabbits. METHODS Intraocular pressure fluctuation was measured in 24 eyes of 12 rabbits submitted to vitrectomy, phacofragmentation and phacoemulsification procedures (eight eyes per group). The procedures were divided according to the force of aspiration of the instrument. Intraocular pressure was monitored with a computerized polygraph by means of a cannula introduced into the vitreous chamber. RESULTS Intraocular pressure showed a mean variation from 33 mmHg (maximum) to 6 mmHg (minimum). Vitrectomy showed the greatest difference between weak and strong aspiration. The greatest fluctuations occurred during procedures with strong aspiration, with phacoemulsification showing the widest variation, with maximum peaks almost reaching 50 mmHg. The infusion pressure varied less than the intraocular pressure, especially at the lowest pressures. CONCLUSIONS The fluctuation of intraocular pressure during ocular surgeries was not great. The higher the aspiration pressure, the higher the intraocular pressure. The infusion pressure did not show a good correlation with intraocular pressure.