Silicone oil flowability rates through a standard 23G vitrectomy system

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 1000cs and 5000cs,manufactured by multinational / national manufacturers in Pakistan, were compared. Oils of 1000cs/500cs 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 ands 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 1000cs 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 5000cs were between 335.7 seconds and 802.0 seconds at 40 mmHg and between 169.6 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. (author)