Purpose. We hypothesized that reaction times (RTs) for a switch release are faster for hand-controlled than for foot-controlled switches for physiological and anatomical reasons (e.g., nerve conduction speed). The risk of accidental trauma could be reduced if the surgeon reacted quicker and therefore improve the surgical outcome. Method. We included 47 medical professionals at USC. Demographics and handedness were recorded. Under a microscope, a simple reaction time test was performed, testing all extremities multiple times in a random order. Additionally, a subjective questionnaire was administered. Results. The mean RTs for hands are 318.24 ms ± 51.13 and feet 328.69 ± 48.70. The comparison of hand versus foot showed significant shorter RTs for the hand (P = 0.025). Partially significant differences between and within the experience level groups could be demonstrated by level of education (LE) and microscopic surgeries/week (MSW) (P = 0.57–0.02). In the subjective questionnaire, 91.5% (n = 43/47) of test subjects prefer to use hand controls. Conclusion. Our data show that the RT for hands is faster than feet. Similarly the subjective questionnaire showed a greater preference for hand actuation. This data suggest a hand-controlled ophthalmic instrument might have distinct advantages; however, clinical correlation is required.

Background: Dual pneumatic systems use two separate air line tubes to open and close the cutter and can achieve high cut rates. The purpose of this study is to evaluate the influence of gauge size, cut rate and aspiration on the flow rate performance of ultra high-speed cutters operated with a commercially available dual pneumatic vitrectomy system. Methods: Analysis of a high-speed video was used to determine duty cycle. Flow rates from 20-, 23- and 25-gauge cutters were calculated in predetermined conditions of aspiration levels and cut rates; water and fresh porcine vitreous samples were studied. Results: For all three gauges of cutters, the duty cycle and water flow showed an inverse correlation with increasing cut rates and a direct correlation with increasing aspiration levels (p < 0.05). Vitreous flow rates from all gauges increased with increasing aspiration and cut rates (p < 0.05). Conclusion: Larger gauges of the cutters as well as higher aspiration and cut rate levels resulted in improvement of the vitreous flow rates. A good understanding of the different flow rate settings is essential for the surgeon and optimizes the safety of surgical procedures.

Purpose Determine the performance of dual pneumatic ultra high-speed 23-gauge cutters operated with variable duty cycle (DC) settings. Methods Frame-by-frame analysis of high-speed video was used to determine the DC in core, 50-50 and shave modes. Using three cutters at various cycles per minute (CPM) and aspiration levels, mass of water or vitreous removed from a vial was measured within a specified time period. Average flow rates were calculated for each aspiration level and cut-rate with the different DC options. Results The DC increased with increasing cut rate in shave mode, was relatively stable in the 50-50 mode and decreased for the core mode. The DC converged at 5000 CPM for the three different modes. Water flow curves followed the DC variation. Vitreous flow rates for all the DC modes increased with increasing cut rates and peaked at 5000 CPM (P<0.05). The results of the 50-50 mode, that had isolated the DC influence, showed that increasing aspiration and/or cut rate, independently increased the vitreous flow rate. Conclusion Progressive values of aspiration and/or cut rate, increases the vitreous flow rate, independently of the DC. DC control also has an important effect on the vitreous flow; but this effect was reduced at high cut rates due to convergence of the DC modes.

The traction was directly proportional to the aspiration vacuum and inversely proportional to the cut rate. The cutter traction force increased with proximity to the retina.

Using IOPc feature turned ON, 23- and 25-gauge probes were effective in reestablishing and sustaining baseline infusion pressures, although 23-gauge probes showed less IOP fluctuation than did 25-gauge probes.

A pair of closely spaced IrO2 electrodes covered by a polymer film is employed as a new solid-state microsensor for CO2 gas at 1 atm and room temperature. Its function is based on IrO2 sensitivity to the pH-lowering effect produced by CO2 equilibration in the polymer film. This sensitivity is made “asymmetric” by leaving one IrO2/polymer “masked” to CO2 gas exposure. The potential difference is measured and found to be reversible and reproducible for the concentration determination of CO2 between ∼0.1–100% CO2 in N2. Since the microsensor shows fast response, it can also be employed in transient flow-injection experiments for the volumetric analysis of CO2. When calibrated carefully and used with care, the new microsensor based on IrO2 is capable of measuring either the concentration or volume of CO2 with high precision and negligible baseline drift.

The present study establishes a new reproducible technique to quantify vitreoretinal traction during vitrectomy and 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.

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