Silicone oil flowability rates through a standard 23G vitrectomy system

Objective: To compare the viscosity of silicone oils made by different manufacturers by comparing the flow rates through a standard 23G millennium vitrectomy system.

Study Design: Quasi experimental study.

Place and Duration of Study: Department of Ophthalmology, Lahore General Hospital Lahore, Pakistan during 2012.

Patients and Methods:  Viscosities of silicone oils of 1000 cs and 5000 cs, manufactured by multinational/national manufacturers  in  Pakistan,  were  compared.  Oils  of  1000 cs/5000 cs  were  placed  in  20  ml  syringes,  marked randomly and placed in water-VVbaths at 250C, to standardize the control environment. Each syringe was then attached to 23G millennium vitrectomy system and time taken to empty 9 ml of oils at pressures of 40 mmHg and 70 mmHg was noted.

Results: Oils of same centistokes manufactured by different manufacturers behaved differently in terms of their flowability and rates of emptying. The emptying times for 1000 cs oils ranged from 112.1 seconds to 144.4 seconds at 40 mmHg and 60.2 to 70.3 seconds at 70 mmHg, whereas corresponding figures for 5000 cs were between 335.7 seconds  and  802.0  seconds  at  40  mmHg  and  between  16 9.6  seconds  and  348.7  seconds  at  70  mmHg.  The differences at all levels were statistically significant (p< 0.001).

Conclusion: Silicone  oils  of  similar  centistokes  behaved  differently  in  terms  of  their  rates  of  flow  through  a standard 23G vitrectomy system under standard conditions indicating better standardization of the viscosity of silicone oils available in the market.