Quantifying Traction Created by Cutters During Vitrectomy

Abstract

Purpose: : Report on a novel, reliable, real-time method to quantify traction created by cutters during vitrectomy.

Methods: : Fresh porcine eyes were positioned in a specially developed holder and the retinal layers were transfixed with a 0.15-mm steel wire and fixed to the load cell of a strain gauge. Five separate cutters for each drive mechanism and gauge (20-, 23- and 25 gauge) was introduced into the eye at a 45-degree angle and positioned at a distance of 3 and 5 mm from the retina respectively. Data from the strain gauge was acquired and the traction force computed for varying vacuum levels and cut speed parameters. For a control, the experiment was repeated in eyes filled with water and the results were compared to the eyes with vitreous gel.

Results: : For 20-, 23- and 25-gauge pneumatic cutters the vitreoretinal traction increased by 4.96, 3.14 and 3.4 dynes for each 100mmHg increase in vacuum (P < 0.05) respectively. The traction forces decreased by 3.41, 2.85 and 5.71 dynes for each 500 cuts per minutes cpm increased (P < 0.05) for 20-, 23- and 25-gauge respectively. For electrical cutters (20- and 25-gauge) the vitreoretinal traction increased by 7.90 and 3.24 dynes for each 100mmHg increase in vacuum (P < 0.05) respectively. The traction forces decreased by 2.51 and 4.17 dynes for each 500 cpm increased (P < 0.05). No traction was observed with eyes filled with water.

Conclusions: : The present study demonstrates that the effects of aspiration, distance from the retina, and cut rate are crucial factors in the amount of retinal traction created by vitreous cutters. According to our study, all cutters tested apply less force than that necessary to detach the retina from the retinal pigment epithelium.

Keywords: vitreoretinal surgery • vitreous • retina