Flow dynamics of dual blade beveled-tip vitreous cutters during vitreous removal compared with single-blade beveled-tip vitreous cutters

Author: Makoto Inoue (Japan)

Co-authors:

Purpose

A dual-blade vitreous cutter with additional opening port of the inner tube of the cutter appears to produce continuous aspirating flow by increasing duty cycle. The purpose of this study is to compare the flow dynamics of dual- or single-blade beveled-tip vitreous cutters during vitreous removal by a high-speed camera.

Setting/Venue

Laboratory investigation, single academic institute

Methods

The aspiration rates of swine vitreous were measured for 25-gauge and 27-gauge beveled dual-blade vitreous cutters (HYPERVIT, Alcon laboratories, TX) or single-blade vitreous cutters. The flow dynamics at maximal cutting rates of diluted vitreous with balanced salt solution (1:1) were recorded with video images of a high-speed camera (HAS-D71, DITECT, Tokyo). Fluorescent polymer microspheres were mixed with diluted vitreous to make the flow visible. A slit-beam of green laser was projected vertically to create a cross-sectional image of the movement of the fluorescent microspheres. The mean aspirating flow was recorded from a lateral view against the opening port and the velocity and the angle of the flow were measured in an area of 2.5 x 2.5 mm for diluted vitreous. The proximal/distal sides of the cutter were defined as body/tip (head) sides of the cutter.

Results

The aspirating flow rate for swine vitreous by the 25-gauge dual-blade cutter at an aspirating pressure of 650 mmHg was significantly higher at 10,000 cpm (P=0.009) and at 20,000 cpm (P=0.001) compared to that by the single-blade cutters at 5,000 and 10,000 cpm with increases of 42% (P <0.0001) and 46% (P <0.0001) respectively. The aspirating flow rate for swine vitreous by the 27-gauge dual-blade vitreous cutter was significantly higher at 10,000 cpm (P=0.010) and at 20,000 cpm (P <0.0001) than that by the single-blade vitreous cutters at 5,000 and 10,000 cpm with increases of 47% (P=0.0104) and 55% (P <0.0001) respectively. The mean velocity in the 2.5 mm x 2.5 mm area in front of the cutter with the lateral view indicated a significantly greater aspiration velocity with the 25-gauge and 27-gauge dual-blade vitreous cutters than that with 25-gauge and 27-gauge single-blade vitreous cutters (P=0.018, P=0.048, respectively). The angle of the aspirating flow with the 25-gauge dual-blade vitreous cutter was significantly greater on the proximal side than that of 25-gauge single-blade vitreous cutters (P=0.006), but the angle with the 27-gauge dual-blade vitreous cutter was significantly lower than that of 27-gauge single-blade cutters on the distal side (P=0.006).

Conlusions

The dual-blade beveled-tip vitreous cutters aspirate a greater volume of vitreous removal at higher velocity than the single-blade beveled-tip vitreous cutters. The aspirating flow of the vitreous with dual-blade vitreous cutter of a smaller gauge may enhance the effect of the oblique angle of the cutter tip to produce stable flow similar to aspirating flow of balanced salt solution on the distal side.