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O. Magalhaes, Jr., L. Chong, C. DeBoer, P.R. Bhadri, J. Lescoulie, M. McCormick, A. Barnes, M. Humayun; Improved Understanding Of Vitrectomy: Qualitative High Speed Video Analysis Of Vitreous Movement Around The Aperture Of Vitreous Cutters . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2688.
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© ARVO (1962-2015); The Authors (2016-present)
To study vitreous movement around the aperture of high speed vitreous cutters and to correlate these movements with tip design, variable parameters (vacuum and cutting rate), mechanisms of drive (pneumatic or electric), blade movement (rotation or axial), port size and overall probe size.
The vitreous was removed en bloc from pig eyes obtained within 24 hours of slaughter. Glass microspheres (90 µm to 150 µm– Corpuscular, NY) or Triamcinolone acetonide (40mg/ml– Kenalog Bristol–Meyers Squibb, Co) was dispersed into the vitreous. A high speed (400 frames/second) camera (DALSA, Ontario,CAN) was used to study the 20 gauge and 25 gauge Bausch&Lomb Lightning–Millenium (St Louis, MO), the 20 gauge (1500 and 2500 cpm) and the 25 gauge Alcon Accurus (Fort Worth, TX), and the 20 gauge Alcon Innovit cutters. Different cut rates and vacuum pressures were analyzed.
Video of the following observations will be presented. 1. Electric axial cutter: duty cycle is constant; the time that aperture is open is equal to the time that the aperture is closed.
2. Pneumatic axial cutter: duty cycle varies with cut rate: as the cut speed increases the time that the aperture is open decreases.
3. Axial guillotine cutters: a stuttering movement of vitreous was observed. Upon opening of the aperture, rapid movement of the vitreous was observed. As the cutter remained open, velocity decreased until closure. Proximal and distal movements of vitreous were observed with and without vacuum.
4. Rotary and axial guillotine cutters: entry of vitreous into the aperture was discontinuous and characterized by distinct starts and stops. Paralysis of vitreous movement occurred during several cut cycles. The incidence of paralysis decreases with increasing cut rate. Momentary reversals of vitreous flow are also observed at the aperture. Displacement of vitreous was observed distal to the apertures.
5. Rotary guillotine cutter: rotational movements of the vitreous mimic the rotational movements of the cutter.
The complexity of vitreous movement around the aperture of vitreous cutters requires a more sophisticated analysis if we are to improve our understanding of mechanized vitreous cutting and achieve breakthroughs in cutter design.
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