Phototoxicity to the Retina: Mechanisms of Damage

摘要: Light damage to the retina occurs through three general mechanisms involving thermal, mechanical, or photochemical effects. The particular mechanism activated depends on wavelength and exposure duration of injuring light. transitions between various light may overlap some extent. Energy confinement is a key concept in understanding predicting type produced by given exposure. As energy (either from laser an incoherent source) deposited retina, its penetration through, absorption in, tissue compartments determined wavelength. Strongly absorbing components will tend concentrate energy. effect absorbed largely rate deposition, which correlated with duration. If deposition too low produce appreciable temperature increase tissue, then any resulting necessarily because chemical (oxidative) reactions induced energetic photons (photochemical damage). faster than thermal diffusion (thermal confinement), exposed rises. critical reached (typically about 10°C above basal), occurs. mechanical relaxation can occur (stress thermoelastic pressure wave produced, disrupted shear forces cavitation-nonlinear Very recent evidence suggests that ultrashort pulses nonlinear mechanisms; latter two-photon excitation cellular chromophores. In addition caused directly absorption, toxicity be presence photosensitizing agents. Drugs excited reactive states ultraviolet (UV) visible I (free radical) II (oxygen dependent) mechanisms. Some commonly used drugs, such as certain antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), psychotherapeutic agents, well popular herbal medicines, ocular phototoxicity. Specific effects end points characteristic are described.