Author: Martin Charles
Co-authors: Vara Wuyyuru, Ying Zhu, Kevin Phan, Carrie Garufis
Abstract
Setting/Venue: (45/50 word max):Various laboratory bench tests designed to mimic practical vitrectomy conditions. In this study, real world challenging scenarios during vitrectomy such as proportional reflux, high flow vit probe usage, and injection of dyes, Triesence, Perflourocarbon etc., were simulated at the bench to evaluate the flow dynamics with IOP compensation ON.
Purpose (99/100 word max):
Vitreoretinal surgery has evolved over the last years and control over the fluidics during the posterior segment procedures is a vital factor for surgeons. IOP compensation provides a stable environment for vitreoretinal surgeries. In some cases, negative flow occurs such as injection of dyes, Triesence, or perfluorocarbon. In other scenarios, high flow needs to enter inside the eye to avoid surge; release of scleral indentation, silicone oil aspiration or using high flow dual vitrectomy probes. The purpose of this video is to correlate surgical scenarios from the OR with corresponding controlled bench tests mimicking these scenarios.
Methods (166/200 word max):
A hollow acrylic eye model was set up in five different surgical scenarios:1) injecting Brilliant Blue G (BBG), 2) injecting Triescense, 3) injecting Perfluorocarbon (PFC), 4) during proportional reflux and 5) using high flow with high speed Vit probes. CONSTELLATION® Vision System was used with IOP compensation and infusion pressure setting at 25mmHg. For each injection scenario, 6 runs were performed. For the high flow (300 & 650 mmHg) and the proportional reflux scenarios, 3 different 25G HYPERVIT beveled vitrectomy probes were used with 3 runs per probe.
A syringe pump (Harvard Apparatus, Pump 33) created an injection speed of 6cc/min. A flow sensor (Transonic Systems Inc, 4PXN) was connected to the infusion canula, and a pressure sensor (OMEGA, PX409-001GUSBH) was connected to an eye model to record instant value of flow and IOP inside the eye. Average IOP, average infusion flow rate, average flow transition time, and average IOP transition time were calculated. Transient time was defined as the time period between two stable statuses.
Results (114/200 word max):
During the injection of BBG, Triesense and PFC, the average negative infusion flows were -6.07±0.06, -6.09±0.49 and -6.45±0.04 cc/min and corresponding IOPs were 31.86±0.73, 31.31±1.19, and 31.52± 0.43 mmHg respectively. For proportional reflux scenario, the average negative flow rate and IOP were -5.58±0.22 cc/min and 27.25±0.0.24 mmHg. For high flow aspiration at 300 and 650 mmHg vacuum, average positive flow rates were 8.17±0.26 cc/min and 14.99±0.35 cc/min and IOPs were 25.93±0.37 and 26.80±0.30 mmHg respectively
For all the scenarios, the first and second flow transition times ranged from 1.14±0.10 to 2.29±0.60 sec and 1.04±0.13 to 2.37±0.45 sec; first and second IOP transition times ranged from 0.64±0.21 to 2.82±0.51 sec and 0.66±0.15 to 4.09±0.70 sec.
Conclusion (80/200 word max):
The bench tests mirroring the surgical vitrectomy scenarios gave quantitative measurements on how fluidics works with IOP compensation. The flow rate changes between real-life challenging vitrectomy scenarios and the corresponding bench tests cases were correlated well. The flow and IOP pressure in the eye had an inverse relationship. In a closed system, flow dynamics compliments IOP compensation. This video will enable vitreo-retinal surgeons to understand the relationship between the IOP and flow rate and help them with better management of fluidics during vitrectomies.
Financial Disclosure: Wuyyuru V, Zhu Y, Phan K and Garufis C are employees of Alcon LLC.
