Laser injury: Difference between revisions
| Line 8: | Line 8: | ||
** Dependent on output power, distance from source to target, and beam divergence | ** 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 | ** 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 1 - non-hazardous | ||
: Class 2 - visible laser, aversion response will protect | : Class 2 - visible laser, aversion response will protect | ||
Revision as of 07:46, 16 February 2018
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.