Charles Deboer

Vitreous dynamics: vitreous flow analysis in 20-, 23-, and 25-gauge cutters.

Purpose: 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.

A new dual port cutter system for vitrectomy surgery.

Purpose: To evaluate and compare the performance of several designs of 20-gauge dual port (DP) vitreous cutter tips with a standard 20-gauge single port tip. Methods: Custom 20-gauge pneumatic vitreous DP cutter tips with different sizes and port positions were evaluated through porcine vitreous and water flow rates. Five designed and fabricated DP cutter tips were compared with a normal single port control tip and evaluated by the measurement of water and porcine vitreous flow rates, and surgical examination in enucleated porcine eyes. Results: Some DP tips approached a maximum vitreous and water flow rates, removing water and vitreous faster than the normal control tip. With reference to surgical evaluation, some DP tips performed better than the single port tip for bulk vitrectomy, but none shaved the vitreous base more effectively. Conclusion: The DP cutter system has the potential to increase the flow rates depending on the size and position of the extra port. In the future, the DP cutter may allow the surgeon to perform bulk vitrectomy more efficiently.

Guillotine performance: duty cycle analysis of vitrectomy systems.

PURPOSE To evaluate the duty cycle of different vitrectomy cutters and classify their blade movement. METHODS A precise weighing (0.01 g) high speed (2 samples/s) balance was used to study the 20-gauge and 25-gauge Bausch & Lomb Lightning-Millenium (St. Louis, MO), the 20-gauge (1500 cpm) and the 25-gauge Alcon Accurus (Fort Worth, TX), the 20-gauge Alcon Innovit, and the 23-gauge DORC (Netherlands) cutters. The weight of balanced saline solution (BSS) was recorded in real time using LabView software and then translated into a graph of volume removed versus time. Variable cut rates and vacuum pressures were analyzed in vitreous and BSS. A high-speed (400 frames/s) camera was used to record cutting for each condition. RESULTS Three types of duty cycle were investigated: parabolic incomplete (pneumatic), sinusoid (electric), and trapezoid (double pneumatic). The parabolic incomplete and trapezoid had a decreased duty cycle at 1500 cuts per minute when it was compared to 600 cuts per minute. The sinusoid had no statistical difference between cut rates. CONCLUSIONS Systems showed different performances of duty cycle. This new classification will be useful for improved understanding of vitrectomy in these different systems.

Biomimetic accommodating intraocular lens (IOL)

This work reports a preliminary study of a fully implantable biomimetic accommodative intraocular lens (IOL) structured as a MEMS-valved endocapsular balloon. The biomimetic accommodative IOL is modeled after the geometry of a 29-year-old human lens and fabricated using only biocompatible materials. Successful accommodation, or focusing ability of the lens, is demonstrated in an objective benchtop test bed with enucleated porcine eyes. After surgical implantation of the lens, the focusing muscles of the eye are stretched in a manner consistent with prior work to demonstrate a change in focal power as the muscle is stretched in a manner similar to the natural lens. This work also includes detailed surgical procedures for the insertion and inflation of the lens.