Mechanism study on light induced ocular axial elongation by computational simulation

Excessive elongation of ocular axial length increases the risk of visual impairment such as high myopia. Light is an important factor that influences ocular axial growth. Researchers have performed many experiments on light induced axial elongation, whereas the mechanism of light effect on axial elongation is still unclear. Axial length is determined by sclera growth, which is dependent on the oxygen supply by choroid vessels. Dopamine emitted from retina binds with dopamine transporter and is sent to the choroid layer to control the expansion and contraction of choroid vessels. Combination of dopamine and dopamine transporter has a significant influence on sclera oxygen supply, thus affecting ocular axial length. In this study, computational simulation was performed on the binding of dopamine and dopamine transporter at various temperatures. Configuration of dopamine transporter was calculated by molecular dynamics simulation, and molecular docking of dopamine and dopamine transporter was carried out to clarify docking locations in dopamine transporter. Binding of dopamine and dopamine transporter presents more stable in 37°C than in 40°C and in 43°C, indicating that excessive temperature rise is likely to hamper the binding of dopamine and dopamine transporter. Red light tends to induce temperature rise due to its thermal effect. It is implied that long wavelength light in high intensity is likely to induce axial elongation due to excessive temperature rise inside retina and choroid caused by heat effect.