Vitreous dynamics: vitreous flow analysis in 20-, 23-, and 25-gauge cutters.
OBJECTIVE
To evaluate porcine vitreous flow and balanced saline solution (BSS) flow rates in different vitrectomy systems.


METHODS
Porcine vitreous was obtained within 24 hours of slaughter. A high-speed (2 samples/s) balance, precise to 0.01 g, was used. Variable cut rates and vacuum pressures were analyzed in vitreous and BSS. The vitreous was labeled with glass microspheres and triamcinolone acetonide. A high-speed (400 frames/s) camera was used to record cutting for each condition.


RESULTS
For all cutters, there was no vitreous flow at zero cut rates (off). In 25-gauge cutters, at 500 mmHg of vacuum, the electric cutter produced higher average flow rates at high cut rates (600 cpm, 0.004 mL/s, and 1500 cpm, 0.013 mL/s) than pneumatic, which demonstrated a decreased flow at speeds higher than 1000 cpm (1000 cpm, 0.015 mL/s, and 1500 cpm, 0.006 mL/s). The percentage of vitreous flow rate/BSS flow rate in different aspiration and cut rates showed an ascending curve. This demonstrates evidence of flow obstruction in 25- (all cut rates), 23- (all cut rates), and 20-gauge (all cut rates). Flow obstruction and surge movements were seen in the high-speed videos.


CONCLUSIONS
The vitrectomy systems each illustrate different performances of vitreous removal. The physical characteristics of vitreous resulted in nonuniform flow in all vitreous cutters.
Magalhaes
Octaviano
O
Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA. octavianomj@terra.com.br
Chong
Lawrence
L
DeBoer
Charles
C
Bhadri
Prashant
P
Kerns
Ralph
R
Barnes
Aaron
A
Fang
Sophia
S
Humayun
Mark
M
D000085:Acetates / Q000378:metabolism; D000818:Animals; D004338:Drug Combinations; D008903:Minerals / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D013552:Swine; D014821:Vitrectomy / Q000295:instrumentation*; D014822:Vitreous Body / Q000378:metabolism*
D000085:Acetates; C030660:BSS solution; D004338:Drug Combinations; D008903:Minerals; D012965:Sodium Chloride