Retinal Photodamage by Endogenous and Xenobiotic Agents^†

Abstract

The human eye is constantly exposed to sunlight and artificial lighting. Light transmission through the eye is fundamental to its unique biological functions of directing vision and circadian rhythm and therefore light absorbed by the eye must be benign. However, exposure to the very intense ambient radiation can pose a hazard particularly if the recipient is over 40 years of age. There are age-related changes in the endogenous (natural) chromophores (lipofuscin, A2E and all-trans-retinal derivatives) in the human retina that makes it more susceptible to visible light damage. Intense visible light sources that do not filter short blue visible light (400-440 nm) used for phototherapy of circadian imbalance (i.e. seasonal affective disorder) increase the risk for age-related light damage to the retina. Moreover, many drugs, dietary supplements, nanoparticles and diagnostic dyes (xenobiotics) absorb ocular light and have the potential to induce photodamage to the retina, leading to transient or permanent blinding disorders. This article will review the underlying reasons why visible light in general and short blue visible light in particular dramatically raises the risk of photodamage to the human retina.

Yttrium oxide nanoparticles prevent photoreceptor death in a light-damage model of retinal degeneration

“…In this model there is continuous bleaching of photoreceptor opsin proteins that consecutively absorb radiant energy and cause the excitation of electrons from the ground state to the excited state [25, 35]. Due to the instability of the excited state, the energy is dissipated in different ways.…”

The influences of purple sweet potato anthocyanin on the growth characteristics of human retinal pigment epithelial cells

“…They also participate in converting and storing retinoid, which is necessary for the visual process (17). Due to their unique functions and position, the RPE cells suffer from oxidative stress (18) and light exposure (19). Moreover, RPE dysfunction leads to many devastating retinal diseases, such as age-related macular degeneration (20).…”

Lipofuscins prepared by modification of photoreceptor cellsviaglycation or lipid peroxidation show the similar phototoxicity

“…Average rates of superoxide photogeneration in all experiments are presented in the Table 1. The higher rate of superoxide photogeneration by RPE lipofuscin compared to A2E-containig model lipofuscins could be explained by the presence of other photoactive fluorophores[11,42-44] because the concentration of A2E in RPE lipofuscin does not exceed the concentration of the fluorophore in the model lipofuscins.…”