Posters

Phaco-fluidics: establishing the bottle height and Digiflow adjustment required to compensate for the reduced flow that occurs when switching from 2.5mm to 2.2mm

Poster Details

First Author: L.Maubon UK

Co Author(s):    A. Garg   T. Sharma   P. Ursell              

Abstract Details

Purpose:

We aim to determine the adjustment in bottle height (BH) and infusion pressuring technology (Digiflow) parameters required to compensate for the reduced flow when switching from a 2.5mm to a 2.2mm needle. Current trends lean toward smaller incision cataract surgery. Poiseuille’s law shows that a small decrease in the radius of a phacoemulsification needle will dramatically reduce flow rate. Reduction in flow can be compensated for by increasing BH and Digiflow. This information will be of use for surgeons wishing to utilise smaller phacoemulsification instrumentation, whilst also reinforcing the use of infusion pressuring technology in small incision cataract surgery.

Setting:

Epsom & St Helier NHS Trust, London, England & Maxivision Speciality Eye Hospital , New Delhi, India

Methods:

Flow was obtained through two phacoemulsification needle and sleeve attachments with differing diameters of 2.2mm and 2.5mm. Measurements were observed at bottle heights of 40, 60, 80, 100, 120, 140cm and Digiflow pressures at 25%, 50%, 75% and 100%. Flow was calculated from the time taken to fill a 10 millilitre syringe. Each measurement was repeated 3 times. Averages were plotted and analysed. Data collection was repeated across sites.

Results:

Flow through the smaller phacoemulsification needle and sleeve was unable to match the flow rate achieved by the larger needle overall. Range of flow through the 2.2mm needle was 0.76-2.43ml/sec. Range through the 2.5mm needle was 0.93-2.84ml/sec. At a maximal, BH flow through the 2.2mm needle was equivalent to the 2.5mm needle at just 90cm. Digiflow set to 100% at a maximum BH of 140cm gives an equivalent BH of 277cm. This means the smaller needle and sleeve is able to achieve a flow rate comparable to a 2.5mm needle at an equivalent BH of 208cm (BH plus 50% Digiflow).

Conclusions:

Flow rate through a tube is greatly influenced by radius. Reduction in flow secondary to smaller instrumentation diameter, which cannot be compensated for with BH alone, can be offset with infusion pressuring technology. We were able to identify the BH adjustment and Digiflow parameters which are needed for reducing phacoemulsification needle and sleeve diameter from 2.5mm to 2.2mm. This information can be applied to predict fluid flow to the anterior chamber maintaining stability and improving the success of micro incision cataract surgery.

Financial Disclosure:

NONE