Eye Hazard from Laser and Intense Light
The eye is at particular risk for the following reasons:
- Damage to the retina (back of the eye) is likely to be irreparable
- Damage can occur at large distances from the laser aperture
- Damage can occur from exposure to very low power lasers
- Even reflections can be hazardous
The area of the eye that is susceptible to damage is dependent on the wavelength of the laser or intense light source.
Retinal damage (back of the eye)
Exposure to visible and near infra red light can cause permanent blindness. Even light of relatively low energy can be a hazard to the retina. This is because the lens of the eye focuses light onto a very small point at the back of the eye which greatly increases the intensity. Low power lasers of even a milliwatt can be dangerous.
Only a fraction of the energy is directly absorbed by rods and cones, the remainder being absorbed by melanin in the epithelium. This causes local heating and hence indirect damage to adjacent rods and cones.
If sufficiently intense, this may result in permanent loss of vision, which will be noted by the subject only if the macula is involved. This is likely to occur if the subject was looking directly at the beam. Peripheral loss will only be noted with gross damage or maybe by an ophthalmic examination.
Anterior (front of eye) damage
Very short (less than 315 nm) and very long (more than 1400 nm) wavelengths are absorbed in the cornea. If the damage is superficial and limited to outer layers, then the cornea will repair itself due to fast turnover of surface cells. Some wavelengths (315 to 400 nm and 760 to 1400 nm) will deposit some of their energy in the lens of the eye. This could lead to cataract formation if the energy is sufficiently high.