Laser injury

Background

• Use of lasers in civilian and military applications is increasing
• Military use - range finders, target designators, guidance systems, non-lethal denial, and now being used as directed energy weapons
• Civilian use - laser cutter/engraver, precision measurement, pointers, welding, entertainment
• Potential to cause injury is largely dependent upon irradiance and beam wavelength
• Irradiance
  • Amount of energy that hits the eye/skin per unit area
  • Dependent on output power, distance from source to target, and beam divergence
  • Human eye can focus laser to a very small area on the retina increasing the irradiance by a factor of 100,000

ANSI Classification of Laser

Class 1 - non-hazardous

Class 2 - visible laser, aversion response will protect

Class 3a - eye hazard with optical aids that collect or focus beam

Class 3b - eye hazard, some skin at high power

Class 4 - eye hazard, skin hazard, fire hazard, diffuse reflection hazard

Clinical Features

Eye

Main organ of concern; range of effects as below starting with the most severe to the least; damage from thermal / photochemical / photomechanical process

• Tissue vaporization
• Retinal hemorrhage / ocular holes
• Retinal burn / corneal burn / irreversible scotoma/minimal visible lesion
• Histological damage / irreversible scotoma / cataract
• Nominal ocular hazard distance (NOHD)
  • Distance from laser source which the intensity of a single laser beam becomes safe by not exceeding the maximum permissible exposure
  • Laser is dangerous if viewed from a closer distance than this
  • Can be calculated if power (mW), divergence (mrad), and diameter at aperture (mm) is known
• Flash blindness / after images / reversible scotoma
  • visual loss temporary
  • lasts seconds to minutes
  • similar to flashbulb effect
• Glare/dazzle
  • no permanent damage results
  • similar to driving into the setting sun
• Distraction

Skin

Second organ of concern; effect more dependent on wavelength of laser

• thermal burn - IR, visible, UV-A laser
• photosensitivity - Visible, UV-A laser
• darkening - UV-A laser
• accelerated skin aging - UV-B
• skin cancer/erythema - UV-C

Evaluation

• History
  • Obtain detailed information as to the nature and characteristic of the laser beam exposure
  • Intensity, color, constant or flicker, duration of exposure, location, beam diameter estimate, range, source, location, type of laser, class of laser
• Examination
  • External exam of skin and adenxa looking for burns or evidence of physical trauma
  • Visual acuity near and far
  • Amsler grid test
  • Pupils
  • Stereopsis
  • Color vision
  • Slit lamp examination
  • Retinal (fundoscopic) examination

Management

• As appropriate per history and physical exam findings

Disposition

• Discharge home if normal exam and no persistent symptoms suggestive of laser eye injury
• Consult ophthalmologist if persistent symptoms or positive findings on examination suggesting laser eye injury such as retinal hemorrhage, corneal burn, ocular holes, etc.