Laser Safety Tip - Optical Hazards

By Vanessa Freitas, DDS, ALD Laser Safety Committee Chair

Laser devices should always be handled with care. Depending on the laser’s potential to cause injury to the eyes or skin followed by direct exposure to the beam and/or secondary hazards, the lasers are divided into hazard classes (Class I, II, III and IV).

Most laser beams have a delivery system that will undergo some divergence with distance, despite the concept that laser beam is collimated. Based on the power output, amount of divergence, and beam diameter and configuration, a Nominal Ocular Hazard Distance (NOHD) can be assessed.

The possible risk to human tissue is assessed with regard to the Maximum Permissible Exposure (MPE). This is a value of exposure limit above which tissue damage may occur. The MPE value can be applied relative to laser wavelength, power output, beam diameter, possible focusing of the beam, and target and nontarget tissue or structures. For lasers Classes III and IV, the level of laser radiation that a person is being exposed to is above the MPE, so these lasers pose predictable or instantaneous risk. The area where protective measures must be taken is called the Nominal Hazard Zone (NHZ). The manufacturer has the responsibility of informing the dentist and LSO of the dental laser’s specific NHZ by publishing this information in the operator’s manual.

Considering the potential optical hazard, the use of eye protection when operating lasers of classes III and IV is required in the workplace by the US Occupational Safety and Health Administration (OSHA), since its use may result in eye exposure above the MPE.

The eye is composed of pigmented and nonpigmented tissue that will absorb incident laser radiation relative to the wavelength being used. Damage from a laser beam may be due to direct exposure of the unprotected eye or diffuse reflection if wavelength-specific protective eyewear is not worn. The optical damage may result in:

  • retinal lesion
  • retinal bur and cataract
  • aqueous flare
  • corneal burn

Protective eyewear can protect the eyes from the reflected or scattered laser light with a hazardous beam power, as well as from direct exposure to a laser beam. The eyewear must be selected for the specific type of laser to be used, based appropriate wavelength range, this way, the eyewear can block or attenuate the laser bean. Consequently, it is mandatory that all personnel (clinician, assistant, and patient) within the controlled area of Class IIIB, IIIR, and IV laser use should employ suitable eye protection during laser procedures.
Protective eyewear is rated for optical density (OD), which is the base-10 logarithm of the attenuation factor by which the optical filter reduces beam power. The protective specifications (wavelengths and optical densities) are usually printed on the goggles, generally near the top of the google/glasses. If the eyewear is marked as 810 nm – 2890 nm, then this means that the eyes exposed to all wavelengths between these two outer limits are protected.


Establish a protocol in your office to decrease the chances of causing hazards. For the use of protective eyewear, patient has put on the appropriate laser eyewear as soon as he/she is seated and should not take it off until the patient is leaving the dental operatory at the end of the procedure. The dental operatory personnel must put the eyewear on prior to the laser being turned on and not take them off until the laser is switched off or put into standby mode.


Care must be taken when cleaning laser eyewear and side shields so that their protective coating is not destroyed. The eyewear should be washed with antibacterial soap and dried with a soft cotton cloth in between procedures and patients. Disinfecting solutions generally applied to dental surfaces are too caustic and should be avoided. The eyewear must be inspected frequently to determine whether there is any breakdown (lifting / cracking / flaking) of the protective material that would render the eyewear to be useless. A laser protective eyewear maintenance log should be created with date of inspection, eyewear number, integrity, reason if not compliant and the date new eyewear was ordered. Please refer to ALD Do-It-Yourself Laser Manual for the log example.


Academy of Laser Dentistry Laser Safety Committee. DIY Guide. Do it Yourself Laser Safety Manual. Coral Springs, Fla.: Academy of Laser Dentistry, 2017.



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