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Background <p>The use of artificial models of the eye globe has been proposed as an alternative to human and animal samples for studying drug delivery using intravitreal injections (IVIs). The induced fluid dynamics processes are important in terms of the stress generated at the level of the retina and implications on drugs diffusion.</p> Methods <p>The experiments were performed on an in-scale, 3D printed model of the vitreous chamber with a realistic shape. We simulated the vitreous humor as a Newtonian fluid with a mixture of diethyl phthalate (DEP) and ethanol. A 0.1 mL volume of the same fluid was injected with fixed angle and direction, for a total of 224 experiments, varying the needle size (from 25G to 32G), needle length, fluid viscosity, and operator. We measured the velocity field on a 2D plane containing the injection needles with the Particle Image Velocimetry (PIV) technique. We computed the normal and shear stress exerted by the fluid on the retina.</p> Results <p>The PIV measurements show a jet-shaped flow following the injection, extending from the injection site to the retina. After the impact, a highly rotational recirculating flow develops from the impinging point upwards along the retina towards the lens, with maximum velocities of about 0.1 - 0.3 m/s. Values of maximum normal stress are in the range of 15-100 Pa, mostly due to pressure peaks, with higher values for 31G and 32G needles. The maximum shear stress is estimated to be on the order of 1 Pa. A statistically significant variability is observed in the inter- and intra-operator comparison.</p> Conclusions <p>The observed stresses are comparable with previous numerical and experimental studies investigating the effects of head and eye movements on retinal detachment. However, the measured values are lower than those estimated for the adhesion force of the retina. These results provide complementary information for the development of general guidelines for IVIs administration, specifically regarding the choice of the injection needle.</p>

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Mechanical stresses on the retina induced by intravitreal injections in an artificial model of the vitreous chamber

  • 期刊论文

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  • 发表日期：

    2026年8月1日

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  • Laura Panebianco,
  • Alessandro Stocchino

摘要

Background

The use of artificial models of the eye globe has been proposed as an alternative to human and animal samples for studying drug delivery using intravitreal injections (IVIs). The induced fluid dynamics processes are important in terms of the stress generated at the level of the retina and implications on drugs diffusion.

Methods

The experiments were performed on an in-scale, 3D printed model of the vitreous chamber with a realistic shape. We simulated the vitreous humor as a Newtonian fluid with a mixture of diethyl phthalate (DEP) and ethanol. A 0.1 mL volume of the same fluid was injected with fixed angle and direction, for a total of 224 experiments, varying the needle size (from 25G to 32G), needle length, fluid viscosity, and operator. We measured the velocity field on a 2D plane containing the injection needles with the Particle Image Velocimetry (PIV) technique. We computed the normal and shear stress exerted by the fluid on the retina.

Results

The PIV measurements show a jet-shaped flow following the injection, extending from the injection site to the retina. After the impact, a highly rotational recirculating flow develops from the impinging point upwards along the retina towards the lens, with maximum velocities of about 0.1 - 0.3 m/s. Values of maximum normal stress are in the range of 15-100 Pa, mostly due to pressure peaks, with higher values for 31G and 32G needles. The maximum shear stress is estimated to be on the order of 1 Pa. A statistically significant variability is observed in the inter- and intra-operator comparison.

Conclusions

The observed stresses are comparable with previous numerical and experimental studies investigating the effects of head and eye movements on retinal detachment. However, the measured values are lower than those estimated for the adhesion force of the retina. These results provide complementary information for the development of general guidelines for IVIs administration, specifically regarding the choice of the injection needle.