Change in outflow pathway of porcine eyes in vitro by nonpenetrating filtering surgery

Abstract. Although glaucoma is currently the world's most common cause of irreversible blindness, there is no curative therapy available to date. The major risk factor that can be influenced in order to stop disease progression is the eye pressure (IOP). Therefore early diagnosis of an altered IOP is essential for the goal of preserving vision. A novel IOP measurement principle for a handheld noncontact self-tonometer shall be validated. The measurement principle uses a pressure pulse generated by a loudspeaker to cause vibrations of the eye. In order to reach the required sound pressure, a closed pressure chamber is placed on the human orbit. With a microphone and a displacement sensor the dynamic behavior of the entire system is detected. In this article the abovementioned principle is being analyzed on porcine eyes under laboratory conditions. The combination of the loudspeaker, the pressure chamber, and the eye to be measured can be described as a coupled spring–mass–damper system. It is demonstrated for enucleated porcine eyes that a defined IOP variation leads to a change in the system's damping ratio. Considering only stochastic deviations, the derived standard uncertainty for the determination of the IOP amounts to < 1 mmHg in the physiological range. The in vitro measurements on porcine eyes help the understanding of the underlying physics and demand for further research on the influence of biometric parameters on eye vibrations. However, the laboratory results provide the basis for a gentle noncontact tonometry method with great applicational prospects. Data is currently being collected on human subjects in a clinical trial, to corroborate the measurement principle in vivo.

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Ultrastructural study of the permeability of in-vitro and ex-vivo human models of human arachnoid granulation CSF outflow pathway

Cerebrospinal Fluid Research ◽

10.1186/1743-8454-4-s1-s6 ◽

2007 ◽

Vol 4 (S1) ◽

Author(s):

Deborah M Grzybowski ◽

David W Holman ◽

Shelley A Glimcher

Keyword(s):

Ultrastructural Study ◽

Ex Vivo ◽

Arachnoid Granulation ◽

Human Models ◽

Outflow Pathway

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In vitro mitomycin C absorption and delivery with different sponge materials used in filtering surgery

Clinical Ophthalmology ◽

10.2147/opth.s101345 ◽

2016 ◽

pp. 665

Author(s):

Diana Urbaneja ◽

Antonio Morilla ◽

Elisa Jiménez ◽

Judith Montemayor ◽

Nuria Marcobal ◽

...

Keyword(s):

Mitomycin C ◽

Filtering Surgery ◽

Materials Used

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A Modified In Vitro Method for Aqueous Humor Outflow Studies in Enucleated Porcine Eyes

Journal of Ocular Pharmacology and Therapeutics ◽

10.1089/jop.2006.0057 ◽

2007 ◽

Vol 23 (2) ◽

pp. 124-131 ◽

Cited By ~ 4

Author(s):

Anu Vaajanen ◽

Heikki Vapaatalo ◽

Olli Oksala

Keyword(s):

Aqueous Humor ◽

In Vitro Method ◽

Aqueous Humor Outflow ◽

Porcine Eyes

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Morphometric Study of Wound Healing in a Model of Filtering Surgery with Mitomycin-C

European Journal of Ophthalmology ◽

10.1177/112067219500500304 ◽

1995 ◽

Vol 5 (3) ◽

pp. 168-171 ◽

Cited By ~ 3

Author(s):

L. E. Pablo ◽

T. Ramírez ◽

R. Álvarez ◽

I. González ◽

J. M. Larrosa ◽

...

Keyword(s):

Wound Healing ◽

Mitomycin C ◽

In Vitro Models ◽

Wilcoxon Test ◽

Morphometric Study ◽

Filtering Surgery ◽

Balance Salt ◽

Pigmented Rabbits

Background Failure of filtering surgery may be related to excessive wound healing in the surgical area. This effect diminishes with the use of antimetabolic agents. Mitomycin-C (MMC) has proved to be the most effective drug to reduce myofibroblastic proliferation in experimental in vivo and in vitro models. To our knowledge, the objective changes induced by mitomycin-C in the size of wound healing areas have not been investigated. Methods: Filtering surgery was performed on both eyes of 40 pigmented rabbits. Preoperatively one of the eyes received MMC (0.5 mg/ml), and the fellow eye received balance salt solution as placebo. Animals were killed on days 6, 15, 30 and 58. Microscopic healing areas were measured by digital procedures. The areas of target and fellow control eyes were compared by the Wilcoxon test. Results This study showed significant differences (p<0.05) between treated and untreated groups, the healing are a gradually becoming smaller. Conclusions Objective methods to quantify the microscopic effects of MMC can be useful to improve our knowledge about the action on this antimetabolite and to enable us to adjust more accurately the timing and dosage when applying the drug in glaucoma filtering surgery.

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Isolation and characterization of novel primary cells from the human distal outflow pathway

Scientific Reports ◽

10.1038/s41598-021-83558-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Uttio Roy Chowdhury ◽

Cindy K. Bahler ◽

Cheryl R. Hann ◽

Bradley H. Holman ◽

Michael P. Fautsch

Keyword(s):

Trabecular Meshwork ◽

Distal Region ◽

Proximal Region ◽

Cellular Growth ◽

Model Systems ◽

Type I ◽

Isolation And Characterization ◽

Outflow Pathway

AbstractOcular hypertension occurs due to increased resistance to aqueous humor removal through the conventional outflow pathway. Unlike the proximal region of the conventional outflow pathway, the distal region has not been well studied, mostly due to lack of model systems. Here we describe isolation and characterization of human primary vascular distal outflow pathway (VDOP) cells from the distal region of the conventional outflow pathway. Tissue from the distal region was isolated from human corneo-scleral rims, digested with collagenase type I (100 U/ml) and placed on gelatin coated plates to allow cellular growth in Dulbecco’s Modified Eagle’s Medium (low glucose) containing fetal bovine serum and antibiotic/antimycotic. VDOP cells showed consistent proliferation for up to 7 passages, retained endothelial-like nature of the parent tissues and showed a unique marker phenotype of Lectin+VEGFR2-CD34-NG2- that was distinct from neighboring trabecular meshwork (Lectin+VEGFR2-CD34-NG2+) and Schlemm’s canal (Lectin+VEGFR2+CD34+NG2+) cells. Dexamethasone treated VDOP cells did not express myocilin and did not form cross-linked actin networks, in contrast to trabecular meshwork cells. These data show that VDOP cells are unique to the distal outflow region and can be used as a viable in vitro model system to understand the biology of the distal outflow pathway and intraocular pressure regulation.

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A New Angle on Angle Surgery

European Ophthalmic Review ◽

10.17925/eor.2017.11.01.40 ◽

2017 ◽

Vol 11 (01) ◽

pp. 40

Author(s):

Rhys Davies ◽

Mei-Ling Cheng ◽

Andrew J Tatham ◽

◽

...

Keyword(s):

Intraocular Pressure ◽

High Risk ◽

Visual Loss ◽

Glaucoma Surgery ◽

Filtering Surgery ◽

Advanced Glaucoma ◽

Outflow Pathway ◽

Tube Shunt ◽

Aqueous Outflow ◽

Ab Interno

Glaucoma surgery has long relied on ab externo techniques such as augmented trabeculectomy and tube-shunt procedures. While these have excellent potential to lower intraocular pressure (IOP), they are associated with risks, including hypotony, and are therefore conventionally reserved for those with advanced glaucoma or at high risk of visual loss. Traditional filtering surgery attempts to bypass the eye’s physiological outflow pathway, however new minimally invasive glaucoma surgery (MIGS) procedures have recently been introduced that focus on the angle structures as a target for improving aqueous outflow. There are a growing number of ab interno MIGS procedures that utilise the natural drainage pathways of the eye in the management of glaucoma. This article examines the progress so far and describes how the angle has become a viable target for glaucoma surgery.

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Accuracy of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL in edematous corneas

Therapeutic Advances in Ophthalmology ◽

10.1177/2515841420923190 ◽

2020 ◽

Vol 12 ◽

pp. 251584142092319

Author(s):

George A. Kontadakis ◽

Alexandros Pennos ◽

Iro Pentari ◽

George D. Kymionis ◽

Ioannis G. Pallikaris ◽

...

Keyword(s):

Experimental Study ◽

Intraocular Pressure ◽

Corneal Thickness ◽

Applanation Tonometry ◽

Goldmann Applanation Tonometry ◽

Dynamic Contour Tonometry ◽

Pressure Measurements ◽

Ultrasound Pachymetry ◽

Porcine Eyes

Purpose: To investigate in vitro the accuracy of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL in edematous corneas. Methods: Experimental study included 20 freshly enucleated porcine eyes. Epithelium was debrided, and eyes were divided in four groups. Groups were immersed in 35%, 40%, 50%, and 60% glycerin solutions for 3 hours. Subsequently, globes were mounted in a special holder, and their intraocular pressure was hydrostatically adjusted. Intraocular pressure was measured by means of dynamic contour tonometry, Goldmann applanation tonometry, and Tono-Pen XL while adjusting true intraocular pressure to 17, 33, and 50 mm Hg. Ultrasound pachymetry was performed. Results: Mean corneal thickness was 914.5 ± 33.3 μm (730–1015 μm). In true intraocular pressure of 33 mm Hg, Goldmann applanation tonometry and dynamic contour tonometry significantly underestimated true intraocular pressure (mean Goldmann applanation tonometry: 14.7 ± 4.8 mm Hg, p < 0.001, mean dynamic contour tonometry: 21.6 ± 6.8, p < 0.001). Tono-Pen XL also underestimated, but difference was not statistically significant (Tono-Pen XL: 27.9 ± 9.7, p = 0.064). In true intraocular pressure of 50 mm Hg, all three methods significantly underestimated (Goldmann applanation tonometry: 17.6 ± 5.3 mm Hg, p < 0.001, dynamic contour tonometry: 26.8 ± 6.3 mm Hg, p < 0.001, Tono-Pen XL: 35.6 ± 8.4 mm Hg, p < 0.001). The error in measured intraocular pressure for each method (true minus measured intraocular pressure) was significantly correlated to true intraocular pressure ( p < 0.001). The intraocular pressure measurements of each eye taken under true intraocular pressure of 17 and 33 mm Hg with the three methods were correlated to each other. Measurements taken under intraocular pressure of 50 mmHg were not correlated to each other. Corneal thickness was not correlated to intraocular pressure measurement. Conclusion: Goldmann applanation tonometry, dynamic contour tonometry, and Tono-Pen XL underestimate intraocular pressure when measured under edematous conditions. Tono-Pen XL showed better accuracy, especially in lower true intraocular pressure. The measurement error increases when true intraocular pressure increases in all three methods.

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