Basic knowledge of sunglasses: radiation penetration characteristics in ocular tissues

Sunglasses in addition to can reduce the radiation intensity of visible light, can also reduce the ultraviolet and infrared radiation. Polarized sunglasses can also be used to eliminate the water, snow, reflecting the gravel road surface level. Sunglasses today more endowed with fashionable breath. But the fundamental role of sunglasses is to provide radiation protection for the eyes. Below to introduce the basic knowledge of the sunglasses of radiation penetration characteristics in ocular tissues. Environmental levels of microwave and gamma ( γ) Ray can directly penetrate eye tissue, etc. Anterior segment organization of short-wave ultraviolet ( Ultraviolet) And long wave infrared ( Far infrared) Can be absorbed, uva rays, Near ultraviolet) Can be absorbed by the lens. Visible light and short wave infrared ( Near infrared) Radiation to reach the fundus. Around 800 nm infrared radiation to pass through the cornea and aqueous humor and the lens to the retina. Will these absorbed wavelength radiation effect on morphology and physiological function of eye tissue. To the human eye has a photochemical effect mainly UVA and UVB rays. UVA most is absorbed by the lens, only a small amount can penetrate refractive media to reach the retina; UVB rays mainly is absorbed by the cornea and lens, wavelength at 295 nm, 315 nm radiation can penetrate the cornea and lens to the retina. UVB rays have high photochemical effect, excessive radiation can cause corneal surface within a few hours erythema and stimulating; If in a timely manner to avoid excessive radiation continuously, the effect is temporary and reversible. UVC most block by the ozone layer, general won't cause harm to human body. ( 1) It appears and cornea can absorb almost 100% of the UVC ( < 290海里) , but, with the increase of wavelength, penetrating quickly improve. For example, a 320 - nm ultraviolet radiation corneal penetration rate of 60%. It is generally believed that is greater than 300 nm wavelength ultraviolet radiation by the vast majority of animal species of the cornea. ( 2) Normal young people below the lens can absorb most of the 370 nm uv radiation. As the growth of the age, the color of the human lens gradually turn yellow and begin to absorb more UVA, even a short wavelength visible light, together with atmospheric absorption characteristics of ultraviolet radiation, the lens to absorb ultraviolet (uv) radiation is in the 290 - nm - — 370 nm range, namely, UVA and UVB rays. ( 3) For adults, only less than 1% of the 320 nm - 360 nm 340 nm and 2% of UVA can reach the retina, it also suggests that the lens absorbed reaches the lens of all most of UVB and UVA.