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Rupesh Singh, Madhusudhanan Balasubramanian; Nanoparticle Mediated Efficient Treatment Strategy for Photocoagulation of Retinal and Choroidal Neovascularization of Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3993. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Panretinal photocoagulation of choroidal neovascularization in diabetic retinopathy (DR) has low spatial focus and target efficiency. We propose a novel nanoparticle (NP) mediated laser photocoagulation in DR based on the principle of surface plasmon resonance of Au-Si nanoshells. We study the efficacy in terms of laser power and exposure time to achieve a targeted photocoagulation with our strategy to infuse choroidal locations with NP and without NP infusion.
Numerical simulation of laser photocoagulation in a multilayer ocular tissue comprising of retina, RPE, choroid and sclera was performed. A conjugate bioheat transfer model (BTM) for blood perfused tissues with radiative transfer equation (RTE) for collimated and diffuse radiation model was solved. A finite volume method based solver was developed for BTM incorporating a discrete ordinate method solver for RTE. An accurate axisymmetric cylindrical geometry of porcine eye (Fig. 1) with comprehensive biothermal properties such as thermophysical, blood perfusion, absorption and scattering coefficients was modelled. For exposure time from 5 ms to 500 ms, the retinal layer was irradiated with a 532 nm laser beam of 100 µm radius and power varying from 100 to 200 mW. Gold – Silica NPs of 80 nm diameter and 10-6 volume fraction were used.
In contrast to choroid without NP infusion, we observed a significant reduction in the laser power and exposure time required to achieve a desired retinal coagulation temperature ≥ 55°C. At 100 mW laser power, the temperature of NP infused choroidal tissue layer reached ∼70°C in 50 ms while the tissue without NP infusion was ∼55°C. Thus NP infusion provided an additional significant temperature rise of 15°C with only 50 ms of exposure. For the same exposure time without NP infusion, an additional 100 mW laser power was needed to achieve a similar temperature profile (Fig. 2a). Fig. 2b shows a transient retinal temperature distribution with NP infusion.
Our novel design of a NP infused laser photocoagulation strategy provided a significant decrease in laser power and laser exposure time required for photocoagulation procedure in DR. The proposed treatment strategy shows promise for a more efficient, targeted and a less traumatic method. We are validating our findings using in vitro and in vivo experimental models.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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