The duration of exposure is also an important cause of eye damage.
If the laser is visible wavelength (400 to 700 nm), the beam power is less than 1.0 mW, and the exposure time is less than 0.25 seconds (anaphobic response time), the retina will not be damaged by prolonged beam exposure.
Class 1, Class 2 lasers fall into this category and therefore generally do not cause retinal damage.
However, viewing in beam or specular reflection of class 3 or 4 lasers and diffuse reflection of class 4 lasers may cause such damage because the beam power is too high, in such cases, 0.25 seconds of photophobia is not enough to protect the eyes Not hurt.
For pulsed lasers, pulse duration also affects the likelihood of eye injury. If a pulse with a duration of less than 1 ms is focused on the retina, in addition to the thermal damage mentioned earlier, it can cause severe other physical damage and cause hemorrhage. Today, many pulsed lasers have pulse durations of less than 1 picosecond. The American National Standards Institute's ANSI Z136.1 standard defines the maximum allowable eye exposure (MPE) that is expected to cause eye damage (under specific exposure conditions).
If the MPE is exceeded, the potential for eye injury is greatly increased. Because laser retinal damage can be severe due to the eye's optical gain of about 100,000 times, this means that an irradiance of 1 mW/cm2 entering the eye will increase to 100 W/cm2 by the time it reaches the retina.
Permanent blindness can occur in severe damage after laser exposure. Some symptoms of mild to moderate damage include (just a few examples, other ocular symptoms may also occur): sudden loss of vision; vitreous and/or chorioretinal hemorrhage; Blindness, floaters, etc.; eyes become light-sensitive and easily fatigued; corneal abrasions are accompanied by pain; these symptoms depend on the severity of the injury, and the recovery time can vary from days to months, but if It's a permanent injury, and some symptoms will accompany it permanently.
Contact Person: Mrs. Nica Chow