Definition and Properties of Laser Light

How a Laser Works

Laser Types and Classifications

Laser Biological Hazards

Eyes

Skin

Non-Beam Laser Hazards

Protective Measures - Laser Safety

Protective Equipment

Path to Laser Operation

Test

Laser Links

Laser Biological Hazards

Skin

Skin is the largest organ of the body and, as such, is at the greatest risk for coming in contact with the laser beam.  The most likely skin surfaces to be exposed to the beam are the hands, head, or arms.

Skin Components

• Stratum Corneum (Dead Layer)

  • The stratum corneum is the outermost layer or the horny layer. It consists of flattened, dead epidermal cells that protect the living tissue from water loss, injury from physical objects, and radiant energy. The thickness is 8-20 um except on the soles of the feet and the palms of the hands where it is 500-600 um.

• Epidermis

  • The epidermis is the outermost layer of living tissue, where the tanning process takes place. It has a relatively uniform thickness of about 50-150 um.

• Dermis Corium

  • The dermis corium is made up largely of connective tissue which gives the skin its elasticity and supportive strength. Included in this layer are nerve cells, blood vessels, and lymphatic glands. The thickness of this layer varies over the body from 1-4 mm.

• Subcutaneous Tissue

  • The subcutaneous tissue is made up mostly of fatty tissue serving as insulation and as a shock absorption medium. The thickness of this layer varies according to the area of the body as well as from person to person.

Laser effects on tissue depend on - the power density of the incident beam, absorption of tissues at the incident wavelength, time beam is held on tissue, and the effects of blood circulation and heat conduction in the effected area.

Immediate Effects

As shown above, the immediate effect of exposure to laser light above the biological damage threshold is normally burning of the tissue.  Injury to the skin can result either from thermal injury following temperature elevation in skin tissues or from a photochemical effect (e.g., "sunburn") from excessive levels of actinic ultraviolet radiation.

Delayed Effects

The possibility of adverse effects from repeated or chronic laser irradiation to the skin has been suggested, although it is normally discounted.  Only optical radiation in the ultraviolet region of the spectrum has been shown to cause long-term, delayed effects.  These effects are: accelerated skin aging and skin cancer.  At present, laser safety standards for exposure of the skin attempt to take these adverse effects into account.