LASERs: Visible and IR Flashcards
What are the essential properties of a LASER?
Monochromatic
Small Divergence
Coherent.
What LASER is used in LASIK surgery and why?
EXCIMER LASER
UVC - 193nm
Penetrates to a depth of 0.1mm into the cornea, allowing the cornea to be reshaped but does not penetrate into other parts of the eye.
What LASER is used in the treatment of diabetic retinopathy surgery and why?
Green LASER (e.g. Argon 584nm) Passes through the eye but it is absorbed by the blood sealing the leaks.
What LASER is used in LASER Hair Removal and why?
Red/IR LASER (e.g. Alexandrite 700-800nm)
Passes through dermis and tissue, absorbed by hair follicle.
What LASER is used in LASER surgery (e.g. ENT or Gynae) and why?
Visible or IR (e.g. CO2 10,600nm)
Delicate excisions with minimal collateral damage.
Excision depth of 0.1mm.
What LASER is used in Endoscopic LASER surgery and why?
Ho-YAG 2080nm
Cuts and coagulates with minimal bleeding.
Can destroy urinary stones.
What are the different classes of LASER?
Class 1 - Safe: enclosed or low power (<1mW)
Class 1M - Safe: except with viewing aids.
Class 2 - Safe for accidental viewing: 1mW max in the visible spectrum.
Class 2M - Use of collimating optics may be hazardous.
Class 3R - Intentional intra-beam viewing may be hazardous (Power <5mW)
Class 3B - Eye hazard but no skin Hazard (Power <500mW)
Class 4 - Eye, Skin, and Fire Hazard
Where is data for the calculation of MPE found?
IEC 60825-1
What is the Nominal Ocular Hazard Distance (NOHD)?
The distance within which the MPR may be exceeded, including both specular and diffuse reflection.
What is the equation for NOHD from a LASER?
NOHD = 1000SQRT[Power/(piMPE)]
What is the equation for NOHD from a Fibre?
NOHD = (1/AA)*SQRT[Power/(pi*MPE)] AA = Acceptance angle (0.1-0.4 radians)
What is the equation for the Acceptance angle of a fibre?
AA= = arcsin(NA) NA = numerical aperture
What measures are required for safe working with LASERs?
Classification of the LASER Risk Assessment Designation of a controlled area Adequate Personal Protection. LASER local rules LASER protection Supervisor Contingency plans
What duty holders are required for working with class 3B and class 4 LASERs?
Responsible body (e.g. Trust) (delegates responsibility to LPA/Head of Med Phys) Laser Protection Supervisor Equipment Management (EBME)
What are the duties of the LASER Protection Advisor?
Advises the employer on LASER Saftey matters.
Audits LASER Safety.