scholarly journals Real-time measurement of intraocular pressure variation during automatic intravitreal injections: An ex-vivo experimental study using porcine eyes

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256344
Author(s):  
Ikjong Park ◽  
Han Sang Park ◽  
Hong Kyun Kim ◽  
Wan Kyun Chung ◽  
Keehoon Kim
Keyword(s):  
Intraocular Pressure ◽  
Real Time ◽  
Ex Vivo ◽  
Force Sensor ◽  
Needle Insertion ◽  
Injection Rate ◽  
Insertion Force ◽  
Needle Size ◽  
Iop Elevation ◽  
Injection Rates

Purpose To measure needle insertion force and change in intraocular pressure (IOP) in real-time during intravitreal injection (IVI). The effects of needle size, insertion speed, and injection rate to IOP change were investigated. Methods Needle insertion and fluid injection were performed on 90 porcine eyeballs using an automatic IVI device. The IVI conditions were divided according to needle sizes of 27-gauge (G), 30G, and 33G; insertion speeds of 1, 2, and 5 mm/s; and injection rates of 0.01, 0.02, and 0.05 mL/s. Insertion force and IOP were measured in real-time using a force sensor and a pressure transducer. Results The peak IOP was observed when the needle penetrated the sclera; the average IOP elevation was 96.3, 67.1, and 59.4 mmHg for 27G, 30G, and 33G needles, respectively. An increase in insertion speed caused IOP elevation at the moment of penetration, but this effect was reduced as needle size decreased: 109.8–85.9 mmHg in 27G for 5–1 mm/s (p = 0.0149) and 61.8–60.7 mmHg in 33G for 5–1 mm/s (p = 0.8979). Injection speed was also related to IOP elevation during the stage of drug injection: 16.65 and 11.78 mmHg for injection rates of 0.05 and 0.01 mL/s (p < 0.001). Conclusion The presented data offers an understanding of IOP changes during each step of IVI. Slow needle insertion can reduce IOP elevation when using a 27G needle. Further, the injection rate must be kept low to avoid IOP elevations during the injection stage.

scholarly journals Intraocular pressure elevation precedes a phagocytosis decline in a model of pigmentary glaucoma

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 174 ◽  
Author(s):  
Yalong Dang ◽  
Susannah Waxman ◽  
Chao Wang ◽  
Priyal Shah ◽  
Ralitsa T. Loewen ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
Ex Vivo ◽  
Pigment Dispersion ◽  
Pigmentary Glaucoma ◽  
Fluorescent Microspheres ◽  
Phagocytic Capacity ◽  
Pressure Transducers ◽  
Intraocular Pressure Elevation ◽  
Iop Elevation

Background: Outflow regulation and phagocytosis are key functions of the trabecular meshwork (TM), but it is not clear how the two are related in secondary open angle glaucomas characterized by an increased particle load. We hypothesized that diminished TM phagocytosis is not the primary cause of early ocular hypertension and recreated pigment dispersion in a porcine ex vivo model. Methods: Sixteen porcine anterior chamber cultures received a continuous infusion of pigment granules (Pg), while 16 additional anterior chambers served as controls (C). Pressure transducers recorded the intraocular pressure (IOP). The phagocytic capacity of the trabecular meshwork was determined by fluorescent microspheres. Results: The baseline IOPs in Pg and C were similar (P=0.82). A significant IOP elevation occurred in Pg at 48, 120, and 180 hours (all P<0.01, compared to baseline). The pigment did not cause a reduction in TM phagocytosis at 48 hours, when the earliest IOP elevation occurred, but at 120 hours onward (P=0.001 compared to C). This reduction did not result in an additional IOP increase at 120 or 180 hours compared to the first IOP elevation at 48 hours (P>0.05). Conclusions: In this porcine model of pigmentary glaucoma, an IOP elevation occurs much earlier than when phagocytosis fails, suggesting that two separate mechanisms might be at work.

scholarly journals Intraocular pressure elevation precedes a phagocytosis decline in a model of pigmentary glaucoma

F1000Research ◽  
2018 ◽  
Vol 7 ◽  
pp. 174
Author(s):  
Yalong Dang ◽  
Susannah Waxman ◽  
Chao Wang ◽  
Priyal Shah ◽  
Ralitsa T. Loewen ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
Ex Vivo ◽  
Pigment Dispersion ◽  
Pigmentary Glaucoma ◽  
Fluorescent Microspheres ◽  
Phagocytic Capacity ◽  
Pressure Transducers ◽  
Intraocular Pressure Elevation ◽  
Iop Elevation

Background: Outflow regulation and phagocytosis are key functions of the trabecular meshwork (TM), but it is not clear how the two are related in secondary open angle glaucomas characterized by an increased particle load. We hypothesized that diminished TM phagocytosis is not the primary cause of early ocular hypertension and recreated pigment dispersion in a porcine ex vivo model. Methods: Sixteen porcine anterior chamber cultures received a continuous infusion of pigment granules (Pg), while 16 additional anterior chambers served as controls (C). Pressure transducers recorded the intraocular pressure (IOP). The phagocytic capacity of the trabecular meshwork was determined by fluorescent microspheres. Results: The baseline IOPs in Pg and C were similar (P=0.82). A significant IOP elevation occurred in Pg at 48, 120, and 180 hours (all P<0.01, compared to baseline). The pigment did not cause a reduction in TM phagocytosis at 48 hours when the earliest IOP elevation occurred, but at 120 hours onward (P=0.001 compared to C). This reduction did not result in an additional IOP increase at 120 or 180 hours compared to the first IOP elevation at 48 hours (P>0.05). Conclusions: In this porcine model of pigmentary glaucoma, an IOP elevation occurs much earlier than when phagocytosis fails, suggesting that two separate mechanisms might be at work.

Design and Experimental Evaluation of Mosquito-Inspired Needle Structure in Soft Materials

2020 ◽  
Author(s):  
Sai Teja Reddy Gidde ◽  
Parsaoran Hutapea
Keyword(s):  
Soft Materials ◽  
Force Sensor ◽  
Needle Insertion ◽  
Insertion Force ◽  
Tissue Phantom ◽  
Tissue Interactions ◽  
Needle Structure ◽  
Future Work ◽  
Path Deviation ◽  
Targeting Accuracy

Abstract Insects steer their stingers effortlessly to a specific target and release their venom in a certain path through the skin with minimal pain. These unique traits inspire the idea to develop bioinspired needles to reduce the insertion forces and to decrease the needle path deviation (deflection) for improved targeting accuracy. Our approach in this work focus on the design of mosquito-inspired needle and evaluation of the needle performance using vibration during tissue insertion. The mosquito-inspired needle design specifically consists of maxilla-shaped and labrum-tip design. The insertion force was measured using a force sensor, which was fixed at the needle end to measure the uniaxial force of needles. The applied vibration on the needle was measured along linear axis using piezoelectric actuator with a frequency of 150 Hz and an amplitude of 5μm. The needle was inserted at a constant speed by attaching the needle to a motorized linear stage. It was observed that the insertion forces of the proposed needle design with vibration showed a reduction by 27% compared to that of a conventional needle. This reduction in insertion force means that there is decrease in tissue gel phantom damage and it was also observed that needle bending has reduced due to reduction in bending stiffness of the tissue phantom. Furthermore, the needle insertion tests in real tissues (bovine kidney) considering the proposed needle geometry and vibration will be studied in future work to understand the bioinspired needle-tissue interactions.

Fracture Mechanics Model of Needle Cutting Tissue

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Andrew C. Barnett ◽  
Yuan-Shin Lee ◽  
Jason Z. Moore
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Shear Modulus ◽  
Friction Force ◽  
Ex Vivo ◽  
Strain Curve ◽  
Needle Insertion ◽  
Force Model ◽  
Insertion Force ◽  
Needle Insertion Force

This work develops a needle insertion force model based on fracture mechanics, which incorporates the fracture toughness, shear modulus, and friction force of the needle and tissue. Ex vivo tissue experiments were performed to determine these mechanical tissue properties. A double insertion of the needle into the tissue was utilized to determine the fracture toughness. The shear modulus was found by applying an Ogden fit to the stress–strain curve of the tissue achieved through tension experiments. The frictional force was measured by inserting the needle through precut tissue. Results show that the force model predicts within 0.2 N of experimental needle insertion force and the fracture toughness is primarily affected by the needle diameter and needle edge geometry. On average, the tearing force was found to account for 61% of the total insertion force, the spreading force to account for 18%, and the friction force to account for the remaining 21%.

scholarly journals Raman Spectroscopy Differentiates Each Tissue from the Skin to the Spinal Cord

2016 ◽  
Vol 125 (4) ◽  
pp. 793-804 ◽  
Author(s):  
T. Anthony Anderson ◽  
Jeon Woong Kang ◽  
Tatyana Gubin ◽  
Ramachandra R. Dasari ◽  
Peter T. C. So
Keyword(s):  
Raman Spectroscopy ◽  
Real Time ◽  
Diffuse Reflectance ◽  
Diffuse Reflectance Spectroscopy ◽  
Ex Vivo ◽  
Needle Insertion ◽  
Reflectance Spectroscopy ◽  
Epidural Needle ◽  
Needle Placement ◽  
Porcine Tissue

Abstract Background Neuraxial anesthesia and epidural steroid injection techniques require precise anatomical targeting to ensure successful and safe analgesia. Previous studies suggest that only some of the tissues encountered during these procedures can be identified by spectroscopic methods, and no previous study has investigated the use of Raman, diffuse reflectance, and fluorescence spectroscopies. The authors hypothesized that real-time needle-tip spectroscopy may aid epidural needle placement and tested the ability of spectroscopy to distinguish each of the tissues in the path of neuraxial needles. Methods For comparison of detection methods, the spectra of individual, dissected ex vivo paravertebral and neuraxial porcine tissues were collected using Raman spectroscopy (RS), diffuse reflectance spectroscopy, and fluorescence spectroscopy. Real-time spectral guidance was tested using a 2-mm inner-diameter fiber-optic probe-in-needle device. Raman spectra were collected during the needle’s passage through intact paravertebral and neuraxial porcine tissue and analyzed afterward. The RS tissue signatures were verified as mapping to individual tissue layers using histochemical staining and widefield microscopy. Results RS revealed a unique spectrum for all ex vivo paravertebral and neuraxial tissue layers; diffuse reflectance spectroscopy and fluorescence spectroscopy were not distinct for all tissues. Moreover, when accounting for the expected order of tissues, real-time Raman spectra recorded during needle insertion also permitted identification of each paravertebral and neuraxial porcine tissue. Conclusions This study demonstrates that RS can distinguish the tissues encountered during epidural needle insertion. This technology may prove useful during needle placement by providing evidence of its anatomical localization.

scholarly journals Intraocular pressure elevation precedes a phagocytosis decline in a model of pigmentary glaucoma

2017 ◽  
Author(s):  
Yalong Dang ◽  
Susannah Waxman ◽  
Chao Wang ◽  
Ralitsa T. Loewen ◽  
Nils A. Loewen
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
Ex Vivo ◽  
Pigment Dispersion ◽  
Pigmentary Glaucoma ◽  
Ex Vivo Model ◽  
Phagocytic Capacity ◽  
Pressure Transducers ◽  
Intraocular Pressure Elevation ◽  
Iop Elevation

AbstractPurposeOutflow regulation and phagocytosis are key functions of the trabecular meshwork (TM), but it is not clear how the two are related in secondary open angle glaucomas characterized by an increased particle load. We hypothesized that diminished TM phagocytosis is not the primary cause of early ocular hypertension and recreated pigment dispersion in a porcine ex vivo model.Materials and MethodsSixteen porcine anterior chamber cultures received a continuous infusion of pigment granules (P), while 16 additional anterior chambers served as controls (C). Pressure transducers recorded the intraocular pressure (IOP). The phagocytic capacity of the trabecular meshwork was determined by fluorescent microspheres.ResultsThe baseline IOPs in P and C were similar (P=0.82). A significant IOP elevation occurred in P at 48, 120, and 180 hours (all P<0.01, compared to baseline). The pigment did not cause a reduction in TM phagocytosis at 48 hours, when the earliest IOP elevation occurred, but at 120 hours onward (P=0.001 compared to C). This reduction did not result in an additional IOP increase at 120 or 180 hours compared to the first IOP elevation at 48 hours (P>0.05).ConclusionIn this porcine model of pigmentary glaucoma, an IOP elevation occurs much earlier than when phagocytosis fails, suggesting that two separate mechanisms might be at work.

scholarly journals Real-time intraocular pressure measurement during phacoemulsification in dogs ex vivo

2015 ◽  
Vol 77 (6) ◽  
pp. 685-692 ◽  
Author(s):  
Seonmi KANG ◽  
Sangwan PARK ◽  
Hyunwoo NOH ◽  
Jiyoon KWAK ◽  
Kangmoon SEO
Keyword(s):  
Intraocular Pressure ◽  
Real Time ◽  
Pressure Measurement ◽  
Ex Vivo
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