scholarly journals Predicting infusion pressure during pars plana vitrectomy: a physically based model

2019 ◽  
Vol 2 (3) ◽  
pp. 88-103
Author(s):  
Tommaso Rossi ◽  
Giorgio Querzoli ◽  
Giampiero Angelini ◽  
Alessandro Rossi ◽  
Carlo Malvasi ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Pars Plana Vitrectomy ◽  
Statistical Significance ◽  
Polynomial Equation ◽  
Head Loss ◽  
Infusion Pressure ◽  
Physically Based ◽  
Pars Plana ◽  
Best Fit

Purpose: Intraocular pressure (IOP) during pars plana vitrectomy (PPV) decreases as aspiration generates flow, a phenomenon known as head loss. Since direct measurement of the IOP during surgery is impractical, currently, available compensating systems infer IOP by measuring infusion flow rate and estimating corresponding pressure drop. The purpose of the present paper is to propose and validate a physically based algorithm of the infusion pressure drop as a function of flow. Methods: Complete infusion lines (20G, 23G, 25G and 27G) were set up and primed. The infusion bottle was set at incremental heights and flow rate measured 10 times and recorded as mean Å} SD. Overall head loss (OHL) was defined, according to hydraulics laws, as the sum of frictional head loss (FHL; i.e., pressure drop due to friction along tubing) and exit head loss (EHL). The latter is equal to the kinetic energy of the exiting flow through the trocar (FKE = V2/2g). A 2nd degree polynomial equation (i.e., ΔP = aQ2 + bQ, where ΔP is the pressure drop, or OHL, and Q is the volumetric flow) was derived for each gauge and compared to experimental data 2nd order polynomial best-fit curve. Results: Ninety-seven percent of the pressure values for all gauges predicted using the derived equation fell within 2 SD of the mean difference yielding a Bland-Altman statistical significance when compared to 91% of best fit curve. Conclusion: The derived equations accurately predicted the head loss for each given infusion line gauge and can help infer IOP during PPV.

Effect of Drip Line Hydrocyclone Design on Head Loss for Agricultural Irrigation

2017 ◽  
Author(s):  
Christian Ramirez ◽  
Deify Law
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Water Flow Rate ◽  
Head Loss ◽  
Drip Line ◽  
Agricultural Irrigation ◽  
Ansys Fluent ◽  
Pressure Drops ◽  
Current Design ◽  
Volume Method

In the present work, computational fluid dynamics (CFD) analysis of an existing drip line hydrocyclone is performed in order to improve the current design for agricultural irrigation by understanding the effect of water flow rate on pressure drop and head loss. When water flows through a pipe, the pressure continuously drops in the stream-wise direction because of friction along the walls of the pipe. It is common to express this pressure drop in terms of an irreversible head loss. Numerical simulations are performed using the commercial CFD code ANSYS FLUENT with the finite volume method. The pressure drops of the hydrocyclone are computed numerically and they are in reasonable agreement with the experimental data provided by the Center for Irrigation Technology at Fresno State. For example, the measured pressure drop across the part is approximately 2.76 × 104 Pa at 1.89 × 10−4 m3/s inlet flow rate whereas the numerical pressure drop is roughly 2.62 × 104 Pa at 1.89 × 10−4 m3/s. Additionally, the present work shows head loss reduction by making changes to the existing hydrocyclone design including the length and diameter of the cavity as well as length of the outlet tube.

scholarly journals Development and Evaluation of Low Cost Drip Filter

2020 ◽  
pp. 87-94
Author(s):  
Balaji Kannan ◽  
N. Janani ◽  
S. Thangamani ◽  
A. Selvaperumal
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Irrigation System ◽  
Low Cost ◽  
Water Productivity ◽  
Head Loss ◽  
Single Chamber ◽  
Uniformity Coefficient ◽  
Sand Particles ◽  
Micro Irrigation

Irrigation water is many a time contaminated with physical, chemical and biological impurities. Proper filtration is of paramount importance to prevent clogging in drip irrigation system thereby aiding in reduced maintenance of the micro irrigation system. This study was conducted on Development and Evaluation of Low cost filters in the Network project on “Engineering Interventions in Micro Irrigation Systems (MIS) for improving water productivity” under Consortia Research Platform on Farm Mechanization and Precision Farming during 2018 to 2020. The objectives of the study are to develop low cost filters and to test the developed system in the field for efficiency in terms of pressure drop throughout discharge and quality of output. It was observed that the discharge from the filter increases as the time increases. Pressure drop and head loss in the filter system increases with flow rate. Filtration efficiency is a percentage of sand particles divided by the TSS removed by the filter. Efficiency of the filter increased from 25% to 64% (double chamber filter) and 23% to 62% (single chamber filter) with flow range of 5 m3/h to 30 m3/h. As flow rate increases, soil particles retained and efficiency of the filter increased with increase in head loss. Filter materials and screen filter removed the sand particles effectively. Uniformity coefficient of 0.95 was observed in single chamber filter which is suitable for small farm application.

Effect of phacoemulsification on outcomes after vitrectomy with membrane peeling regarding new intraretinal cystoid changes and transient macular edema

2020 ◽  
Author(s):  
Christoph Leisser ◽  
Nino Hirnschall ◽  
Oliver Findl
Keyword(s):  
Optical Coherence Tomography ◽  
Macular Edema ◽  
Retrospective Analysis ◽  
Prospective Studies ◽  
Pars Plana Vitrectomy ◽  
Statistical Significance ◽  
Optical Coherence ◽  
Epiretinal Membranes ◽  
Membrane Peeling ◽  
Pars Plana

Purpose: Aim of the present study was to analyze the effect of phacoemulsification on outcomes among patients undergoing vitrectomy with membrane peeling for idiopathic epiretinal membranes, with respect to new postoperative intraretinal cystoid changes and early transient macular edema. Procedures: This retrospective analysis included patients from six prospective studies, examining outcomes of 23G pars plana vitrectomy with membrane peeling due to idiopathic epiretinal membranes. Phacovitrectomy with membrane peeling was performed only in case of coexisting vision affecting cataract. Optical coherence tomography was performed prior to surgery, in the first week and 3 months after surgery. Results: In total, 183 patients were included. Occurrence of new postoperative intraretinal cystoid changes and early transient macular edema showed a trend to be higher among patients undergoing phacovitrectomy with membrane peeling, compared to vitrectomy with membrane peeling alone, but did not reach statistical significance (p=0.5 and p=0.186). Final BCVA 3 months after surgery was significantly lower among patients with new postoperative intraretinal cystoid changes, compared to patients without (with a median difference of 1 line between groups, p=0.016). Conclusions: New postoperative intraretinal cystoid changes and early transient macular edema are more frequent among patients undergoing phacovitrectomy with membrane peeling, compared to patients with vitrectomy with membrane peeling alone.

Transscleral Extraction of an Intraocular Foreign Body From the Posterior Segment of the Eye Without Pars Plana Vitrectomy

2020 ◽  
Vol 76 (1) ◽  
pp. 14-23
Author(s):  
Štěpán Rusňák ◽  
Lenka Hecová
Keyword(s):  
Foreign Body ◽  
Pars Plana Vitrectomy ◽  
Young Patients ◽  
Vitreous Body ◽  
Visual Control ◽  
Intraocular Foreign Body ◽  
Survey Study ◽  
Surgical Method ◽  
Eye Trauma ◽  
Pars Plana

Purpose: Penetrating eye trauma with an intraocular foreign body is very frequent, especially in men in their productive age. Pars plana vitrectomy would be the standard surgical method at our department. However, in indicated cases (metallic intraocular bodies in the posterior eye segment in young patients with well transparent ocular media without detached ZSM and without any evident vitreoretinal traction) transscleral extraction of the intraocular foreign body is performed using the exo magnet, eventually endo magnet with a minimal PPV without PVD induction under the visual control of endo-illumination. Materials and Methods: Between June 2003 and June 2018, 66 eyes of 66 patients diagnosed with a penetrating eye trauma caused by an intraocular foreign body located in the posterior eye segment were treated. In 18 eyes (27,3 %) with a metallic foreign body in vitreous (body) or in retina, no PPV or a minimal PPV without PVD was used as a surgical method. In the remaining 48 eyes (72,7 %), a standard 20G, respectively 23G PPV method were used together with PVD induction and the foreign body extraction via endo or exo magnet. Conclusions: As demonstrated by our survey/study, in the cases of a thoroughly considered indication an experimented vitreoretinal surgeon can perform a safe NCT transscleral extraction from the posterior eye segment via exo magnet, eventually endo magnet under the visual control of a contact display system with a minimal PPV. Thereby, the surgeon can enhance the patient´s chance to preserve their own lens and its accommodative abilities as well as reduce the risk of further surgical interventions of the afflicted eye.

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