July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Relationship between episcleral venous pressure, intraocular pressure and trabecular meshwork resistance: a mathematical model
Author Affiliations & Notes
  • Sunu Mathew
    Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Alon Harris
    Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Alice Chandra Verticchio Vercellin
    Ophthalmology, University of Pavia, Italy
    IRCCS - Fondazione Bietti, Italy
  • Barbara Wirostko
    Moran Eye Center, Salt Lake City, Utah, United States
  • Bruce Martin
    Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States
  • Giovanna Guidoboni
    University of Missouri, Missouri, United States
  • Footnotes
    Commercial Relationships   Sunu Mathew, None; Alon Harris, AdOM (C), AdOM (I), CIPLA (C), Oxymap (I), Shire (C); Alice Chandra Verticchio Vercellin, None; Barbara Wirostko, EyeGate (I), EyeGate Pharmaceuticals (E); Bruce Martin, None; Giovanna Guidoboni, None
  • Footnotes
    Support  University of Missouri
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 3191. doi:
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      Sunu Mathew, Alon Harris, Alice Chandra Verticchio Vercellin, Barbara Wirostko, Bruce Martin, Giovanna Guidoboni; Relationship between episcleral venous pressure, intraocular pressure and trabecular meshwork resistance: a mathematical model. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3191.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Lowering the intraocular pressure (IOP) represents the mainstay of the treatment of glaucoma, via decreasing the production of aqueous humor or enhancing the uveoscleral outflow. Novel mechanisms of IOP reduction independent from the uveoscleral outflow and the aqueous production are under investigation, such as approaches targeting the trabecular meshwork (TM) and reducing the episcleral venous pressure (EPV). Our mathematical model investigates the relationship between EPV, IOP, and TM resistance in order to provide a quantitative estimate of their combined effect.

Methods : A mathematical model is used to simulate aqueous humor flow. The model leverages the analogy between transport of mass and flow of an electric current (Figure 1). IOP is calculated as the result of the balance between (i) AH inflow (Jin) due to ultrafiltration and active secretion; and (ii) AH outflow (Jout) via uveoscleral and TM pathways. In particular, the TM resistance is modeled as Rtm = R0 + Q (IOP-EVP), where R0 and Q are given parameters.

Results : The baseline values used in the model are EVPb = 8 mmHg, R0,b = 2.2 mmHg min/µl, which result in baseline IOPb value of 15 mmHg (Figure 2, dashed line). Figure 2 shows the simulation of IOP levels for different EVP values with normal (R0=R0,b, blue curve) and increased (R0=3R0,b, red curve; R0=6R0,b, yellow curve) levels of TM resistances. The model predicts that reducing EVP would have a different effect on IOP depending on the TM resistance level. For example, reducing EVP from 12 to 8 mmHg would lead to an IOP reduction of 14.8%, 6.3% or 3.1% depending on whether R0=R0,b, R0=3R0,b or 6R0=R0,b.

Conclusions : Our mathematical model suggests that medications that modulate EVP may have a different efficacy in reducing IOP depending on the level of obstruction that is present in the trabecular meshwork.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Schematic of the mathematical model

Schematic of the mathematical model

 

Simulated effect of EVP changes on IOP for different levels of TM resistance

Simulated effect of EVP changes on IOP for different levels of TM resistance

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