Dynamic IOP measurements track changes during phaco

July 1, 2007

A comparison of dynamic IOP values during cataract extraction by phacoemulsification using high and low flow found that lower bottle heights result in lower fluctuations of IOP. An enhanced fluidics management system allows the use of a lower bottle height with concomitant use of high vacuum and aspiration flow rate, without compromising the stability of the anterior chamber.

Key Points

San Diego-A comparison of dynamic IOP values during cataract extraction by phacoemulsification using high and low flow found that lower bottle heights result in lower fluctuations of IOP, according to Abhay Vasavada, MS, FRCS.

"IOP measurements provide information to help better understand fluid dynamics during phacoemulsification. IOP is dependent on irrigation fluid input and output, and it is important to maintain a balance between infusion and aspiration parameters to reduce IOP fluctuations," Dr. Vasavada explained, emphasizing the clinical relevance of IOP measurements. He is director, Iladevi Cataract & IOL Research Centre and chief, Raghudeep Eye Clinic, Ahmedabad, India.

The IOP values were measured using a sensor attached to a pressure transducer. Measurements from the oscilloscope were overlaid as graphs onto the surgical video-observable in real time on a viewing monitor-and recorded.

Sixty patients were divided into one of the six following groups of 10 patients each:

Dr. Vasavada explained that the enhanced fluidics management system had the same cassette design as the currently used one with one difference: more stiff aspiration tubing to reduce surge. IOP measurements were monitored continuously during the sculpting, nuclear division, and fragment removal.

With low fluidics, a vacuum rate of up to 400 mm Hg, aspiration flow rate of 25 ml/min, and bottle height of 70 to 90 cm were used; with high fluidics, the vacuum was set up to 650+ mm Hg, the aspiration flow rate was 40 ml/min, and the bottle height was 90 to 110 cm.

All patients underwent microcoaxial phacoemulsification using a 2.2-mm incision and longitudinal ultrasound (ultrasound power, 60%; microbursts, 20 milliseconds).

He reported that in group 1, in which the current fluidics management system was used with low fluidics, the maximum and minimum IOP values were 75 and 46 mm Hg, respectively. In group 2, with the current fluidics management system and high fluidics, the IOP values were 79 and 38 mm Hg; in group 3, with the enhanced fluidics management system and low fluidics, 72 and 41 mm Hg; in group 4, with the enhanced fluidics management system with high fluidics, 81 and 39 mm Hg; in group 5, with the current fluidics management system and high fluidics with a low bottle height, 82 and 34 mm Hg; and in group 6, with the enhanced fluidics management system, high fluidics, and low bottle height, 75 and 40 mm Hg.