Anderson Teixeira

Vitreoretinal Traction Created by Conventional Cutters during Vitrectomy

PURPOSE To quantify the vitreous traction created by pneumatic (20-, 23-, and 25-gauge) and electric cutters (20- and 25-gauge) during vitrectomy. DESIGN Experimental study. PARTICIPANTS This is a preclinical study, and no patients were involved. METHODS Five separate cutters for each drive mechanism and gauge (20-, 23-, and 25-gauge pneumatic and 20- and 25-gauge electric) were used for each cut speed at predetermined aspiration rates. The retinal layers of fresh porcine eyes were transfixed with a 0.15-mm steel wire and fixed to the load cell of a strain gauge. The cutter to be assessed was introduced into the eye by a micromanipulator at a 45-degree angle adjacent to the retina. The traction force was determined and evaluated at a distance of 3 and 5 mm from the retina with different vacuum and cut rates. MAIN OUTCOME MEASURES Vacuum, cut speed, force (dynes), distance (millimeters), vitreoretinal traction, and gauge. RESULTS The 20-, 23-, and 25-gauge pneumatic cutters have a range of traction from 2.06 to 37.22 dynes, 3.85 to 15.38 dynes, 5.13 to 27.91 dynes, respectively. The 20- and 25-gauge electric cutters have a range of traction from 3.60 to 41.78 dynes and 5.28 to 27.91 dynes, respectively. All results are related to distance, cut, and aspiration rate. With an increase of 100 mmHg of vacuum/aspiration, the traction increased from 7.89 to 3.14 dynes (e.g., 4.96 for 20-gauge pneumatic). The traction decreased as the cut rate was increased, from 5.71 to 2.51 dynes (e.g., 3.41 for 20-gauge pneumatic). CONCLUSIONS The results indicate that retinal traction increased with increasing aspiration vacuum and proximity to the retina; conversely, retinal traction decreased with increasing cut rate. 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. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Performance analysis of ultrahigh-speed vitreous cutter system.

Purpose: To evaluate flow rates and duty cycle for different sizes of ultra–high-speed pneumatic vitreous cutters. Methods: A precision balance measured the mass of water and vitreous removed from a vial. Porcine vitreous was obtained within 12 hours of killed at a local slaughterhouse and kept at 4°C. Twenty-, 23- and 25-gauge (n = 3 of each gauge) pneumatic cutters were tested at 0 (water), 1,000, 2,000, 3,000, 4,000, and 5,000 cuts per minute with aspiration levels of 100, 200, 300, 400, 500, and 600 mmHg. Frame-by-frame analysis of high-speed video was used to determine the duty cycle. Results: Larger gauge cutters associated with higher aspiration levels produced greater vitreous and water flow rates (P < 0.05). As the cut rate increased, the vitreous flow rate increased (maximum flow at 5,000 cuts per minute) and the water flow rate decreased (P < 0.05). The duty cycle of the new-generation cutters decreased as cut speeds increased, using all 3 gauges (P < 0.001). Vitreous flow rates averaged 10 times less than water flow rates using the same cutter at the same settings. Conclusion: Ultra–high-speed vitreous cutters produce consistent vitreous and water flow rates across the tested range of cuts per minute and aspiration levels.

Fluidics in a dual pneumatic ultra high-speed vitreous cutter system.

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.

An experimental protocol of the model to quantify traction applied to the retina by vitreous cutters.

PURPOSE The purpose of this study was to use a novel method to quantify the traction applied to the retina during vitrectomy. METHODS Five 20-gauge electric cutters were used. Fresh porcine eyes were positioned in a specially developed holder and transfixed to the retinal layers with a microwire, and the other end was fixed to the load cell of a strain gauge. The cutter to be assessed was introduced into the eye by a micromanipulator at a 45 degrees angle adjacent to the retina. The traction force was evaluated when the cutter was at 3 and 5 mm from the retina. As control, the experiment was repeated in eyes filled with water, and the results were compared to those when the eyes had vitreous gel. RESULTS Results from the eyes with vitreous gel indicate that retinal traction increased with increasing aspiration vacuum (7.90 dyn for each 100 mm Hg increased; P < 0.05) and proximity to the retina (2.17 dyn; P < 0.05) and decreased with increasing cut rate (2.51 dyn for each 500 cuts per minute increased; P < 0.05). In all eyes filled with water, traction was not observed. CONCLUSIONS 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.

Novel method to quantify traction in a vitrectomy procedure

Aim To report a novel method to quantify traction applied to the retina using vitreous cutters during pars plana vitrectomy. Methods Fresh porcine eyes were positioned in a specially developed holder and transfixed to the retinal layers with a wire and the other end fixed to the load cell of a strain gauge. Five separate 20-gauge electrical drive mechanism vitrectors were introduced into the eye at a 45° angle and positioned at a distance of either 3 or 5 mm from the retina. Data from the strain gauge were acquired and the traction force computed. Results The analysis revealed that the vitreoretinal traction increased by 7.90 dynes for each 100 mm Hg increase in vacuum (p<0.05). The traction forces decreased by 2.51 dynes for each 500 cuts per minute increased (p<0.05) and the traction force increased by 2.17 dynes at 3 mm compared with 5 mm (p<0.05). Conclusion 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.

Ultrasound biomicroscopy in recently postoperative 23-gauge transconjunctival vitrectomy sutureless self-sealing sclerotomy.

Purpose: To evaluate the ultrasound biomicroscopy (UBM) images of recent postoperative 23-gauge vitrectomy using single- and 2-step techniques. Methods: Twelve consecutive eyes were randomized and submitted to 23-gauge sutureless transconjunctival vitrectomy surgery divided in 2 groups: 1) using a beveled trocar to insert the microcannula (single step) and 2) using a stiletto blade to perform first a tunnel incision and then insert the microcannula (2 steps). All patients underwent 3-port vitrectomy with a straight angled incision of 20° to 30°. Ultrasound biomicroscopy examination was performed after 8 days to 10 days of surgery to locate and document the sclerotomy sites. Results: All patients had at least two diameters of the incision measured, and all wounds were constructed obliquely. Single-step sclerotomy mean size was 375.40 μm ± 83.70 μm (range, 280.4–695 μm) and coefficient of variation (CV) was 0.21. Two-step sclerotomy mean size was 315.5 μm ± 56.8 μm (range, 253.2–362.5 μm; CV = 0.26; P = 0.556). Two patients had an intraocular 5,000 centistokes silicone oil injection, one for each group. Only in the single-step incision was silicone oil observed in the wound. Conclusion: Twenty-three-gauge single- and two-step sclerotomies showed no statistical difference in site diameter at UBM. Postoperative UBM examination allowed the evaluation of the wound architecture. A large sample size comparing both surgical techniques should provide a statistical difference.

Association of complement factor H Y402H polymorphism and age-related macular degeneration in Brazilian patients

Purpose:  The aim of this study was investigate the association between complement Factor H polymorphism (Y402H) and age‐related macular degeneration (AMD) in Brazilian patients.

Analysis of a 23-gauge ultra high-speed cutter with duty cycle control.

Purpose: The purpose of the study was to 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 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 the shave mode was relatively stable in the 50–50 mode and decreased for the core mode. The DC converged at 5,000 cycles per minute for the 3 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 5,000 cycles per minute (P < 0.05). The results of the 50–50 mode, which 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 increase the vitreous flow rate, independently of the DC. The DC control also has an important effect on the vitreous flow, but this effect was reduced at high cut rates because of convergence of the DC modes.

Retrochop technique for rock-hard cataracts.

UNLABELLED We describe a recently developed chopper, the retrochopper, and a technique for managing black and brunescent cataracts. The technique enables the surgeon to effectively disassemble the nucleus and perform a safe procedure with a short learning curve. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.

Performance Analysis of Millennium Vitreous Enhancer™ System

BACKGROUND AND OBJECTIVE This study evaluates water and porcine vitreous flow rates and duty cycle using the Millennium Vitrectomy Enhancer (MVE) system (Bausch & Lomb, St. Louis, MO). MATERIALS AND METHODS A precision balance measured mass of water or vitreous removed from a vial within a certain time by 20-, 23-, and 25-gauge MVE cutters at 800, 1,000, 1,500, 2,000, and 2,500 cuts per minute (CPM) with various aspiration levels was studied. Frame-by-frame analysis of high-speed video was used to determine duty cycle. RESULTS Larger cutter and higher aspiration levels produced greater flow rates. Water flow rate showed a parabolic trend peaking at 1,500 CPM and dropping moderately and vitreous flow rate increased moderately with cut-rate increased. The MVE system maintained a high flow rate and high duty cycle even at high cut-rates. CONCLUSION Flow rates for the MVE system are stable and predictable for all cutter gauges, which should aid the surgeon to select the optimal parameters for vitrectomy.