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Nathan Fisher, Cherry Wan; Suprachoroidal Delivery with the SCS Microinjector™: Characterization of Operational Forces. Invest. Ophthalmol. Vis. Sci. 2020;61(7):24.
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© ARVO (1962-2015); The Authors (2016-present)
Suprachoroidal (SC) Injection with the SCS Microinjector is a novel technique to deliver drugs to the posterior segment of the eye, and the tactile feedback of Loss of Resistance (LOR) is critical for the procedure success. Any resistance from operation of the device increases the difficulty to the user to distinguish between resistance due to anatomical location of the needle and resistance from internal friction forces of the device. The purpose of this research is to quantify the force required to operate the SCS Microinjector in a controlled laboratory setting compared to recommended force requirements to operate a standard syringe.
SCS Microinjectors with an 1100 µm needle (30 gauge) were filled with injectate (air, distilled water, and CLS-TA – 40mg/ml triamcinolone acetonide suspension) to nominal capacity (0.1 mL) and then connected to a force gauge to measure the force required to expel the injectate from the device at a controlled rate based on device instructions over 5-10 seconds Glide force, the amount of force required to perpetuate plunger movement within the syringe, and break force, the amount of force required to initiate movement of the plunger within the syringe, were calculated. The measurements were compared to standard reference values found in ISO 7886-1:2017, Sterile Hypodermic Syringes for Single Use.
The glide forces required to inject air (i.e. no injectate), water, and CLS-TA with the SCS Microinjector were 0.19 N, 0.23 N, and 0.73 N, respectively (P < 0.001). The glide forces with all three injectates were significantly lower than the reference maximum value of 5N, according to ISO 7886, indicating that it is easier to actuate the SCS Microinjector than the standard. The average break forces for air and water were 0.43N and 0.41N, respectively (P = 0.314). For CLS-TA, no break force was clearly detected. Similar to the glide force, the break force for the SCS Microinjector was much lower than the standard referenced value of 10N.
Forces to operate the SCS Microinjector using a variety of injectates are far below the international standard recommendations for low-volume hypodermic syringe operation. This may improve the usability of the SCS Microinjector by minimizing resistance forces inherent to the device, therefore allowing the user more accurate tactile feedback with LOR when the suprachoroidal space is reached.
This is a 2020 ARVO Annual Meeting abstract.
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