In vivo detection of hESC-RPE cells via confocal near-infrared fundus reflectance.

BACKGROUND AND OBJECTIVE: To investigate whether the confocal near-infrared reflectance (NIR) imaging modality could detect the in vivo presence of retinal pigment epithelium cells derived from embryonic human stem cells (hESC-RPE) implanted into the subretinal space of the Royal College of Surgeons (RCS) rat. MATERIALS AND METHODS: Monthly NIR images were obtained from RCS rats implanted with either hESC-RPE seeded on a parylene membrane (n = 14) or parylene membrane without cells (n = 14). Two independent, masked investigators graded the images. Histology and immunohistochemistry were performed at different time points (150, 210, and 270 postnatal days of age). RESULTS: NIR images revealed that an average of 20.53% of the parylene membrane area was covered by hESC-RPE. RPE-65 and TRA-1-85 confirmed the presence of human-specific RPE cells in those animals. No areas corresponding to cells were found in the group implanted with membrane only. Intergrader agreement was high (r = 0.89-0.92). CONCLUSION: The NIR mode was suitable to detect the presence of hESC-RPE seeded on a membrane and implanted into the subretinal space of the RCS rat.

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.

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.

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.