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Steven N. Luminais, Shlomit Schaal, Amir Hadayer, William J Foster; Simulated Stress on a Pigment Epithelial Detachment During an Intravitreal Injection. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2318.
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Retinal pigment epithelial (RPE) tears are known clinically to be associated with intravitreal injections in eyes with pigment epithelial detachments (PEDs). We hypothesize that the expansion of the eye at the time of the injection may be the reason for this serious condition. To date, the origin and magnitude of the stress imposed on the retinal tissue by the injection itself has not been well described. This study aims to characterize the stresses the injection causes in the RPE and retina and to assess what impact, if any, changing the duration of the injection has on these forces. Further understanding of these stresses may allow the development of techniques and/or devices to reduce the risk of retinal tears during treatment of PEDs.
A serous PED between Bruch’s membrane and the retina was modeled using COMSOL Multiphysics v5.2a finite element analysis system (Fig 1). Intravitreal injections were modeled by moving the sclera radially outward at a uniform velocity to match the volume increase in a 0.05mL injection. The PED fluid was modeled as water while the vitreous was modeled as a visco-elastic material, as described in the literature.
There are transient periods of oscillating stresses on the retina at the start and end of the simulated injection with a linear increase in stress between the oscillations. The maximum stress was found at the junction between the PED and the normal retina tissue for all injection durations. Maximal retina stress was found at the start of the injection for injection durations 0.25, 0.5 and 1.0 s (80.7, 40.6 and 21.5 N/m2 respectively) while the post injection oscillation produced the largest stress for injection durations 0.75 and 2.5 s (28.2 and 6.7 N/m2 respectively). Injection durations longer than 2.5 seconds did not differ significantly from the results at 2.5s.
Modeling of intravitreal injections demonstrates that the retina is subject to transient stresses at the beginning and end of the injection, with the junction between the PED and the normal retinal tissue being subjected to the largest stress. Different injection lengths modulated the timing of and the maximum stress on the PED.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
The axisymmetric PED model showing layers for the retina, Bruch’s membrane and the sclera.
Maximal von Meiss stress on the retina during a simulated 0.05mL intravitreal injection for different injection durations.
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