LASERS & Lights

ByBeverly Nelson

Outline of Presentation

• Defining LASER• Production of laser• Classification of Laser• Method of application• Biological effects• Clinical indications• Precautions & contraindications

What is LASER ?

• Acronym for Light Amplification of Stimulated Emissions of Radiation

• Relatively new modality which is still undergoing research

Physics of LASER production

• Please read handout provided

• Laser light contains electromagnetic energy

Properties of LASER

• Coherence-

• Monochromaticity

• Collimination

Classification of Lasers

• According to the nature of material placed between the two reflecting surfaces

• Many types of lasers, each with specific wavelength and characteristics

Classification cont’d

• Crystal • Gas• Glass• Semiconductor or diode• chemical

Classification cont’d

• Classification according to high or low power

• Depends on the intensity of energy they deliver

Classification cont’d

• High power lasers or Hot Lasers generate thermal response

• Used in the Medical Realms- surgical cutting

Low level power laser

• Used as a rehabilitation intervention for pain management and wound healing.

• Is relatively new area in medicine (20 – 25 yrs)

• Maximal output of power < 1 milliWatt

Low lever Laser

• Work by producing photochemical rather than thermal effect

Laser light used in Rehab

• There are two types of Laser lights used in rehabilitation

• Helium Neon –HeNe

• Gallium Arsenide -- GaAs

Helium Neon

• Gas laser• Uses a mixture of Helium and Neon in a

pressurised tube

• Creates Laser in the Red portion of the electromagnetic spectrum

Has a wavelength of 632.8nm

Depth of penetration

• Absorbed in the superficial tissues - 2- 5 mm of soft tissue

• Indirect effect at 8 – 10 mm depth of soft tissue

Laser output is affected by

• Care of the equipment

• The number of operating hours

• Quality of fibreoptics used

Gallium Arsenide Laser

• Utilise a diode to produce an infrared ( invisible) Laser

• Wavelength of 904nm 3 – longer wavelength than HeNe

• Absorbed at depths of 1 – 2 cm• Indirect effect of up to 5cm

GaAs Laser

• Has a peak power of 2watts which is delivered in a pulsed mode to decrease the thermal effect

• Greater potential for treatment of deeper soft tissue

Method of application

• There are three methods of application:• Gridding

• Scanning

• Wanding

Biological effects

• Promotes ATP production• Promotes collagen production• Modulates inflammation• Inhibits bacterial growth• Promotes vasodilatation- microcirculation• Alters nerve conduction velocity

Effects of Laser

• Facilitate wound healing • Reduction of pain• Increase tensile strength of star• Decrease in inflammation• Bone response

Clinical indication

• Tissue healing :chronic and acute wounds( can promote tissue repair but more high quality studies needed) accelerated healing

• Arthritis

• Postmasectomy Lymphedema (more evidence needed)

Clinical indication cont’d

• May reduce pain in patients with neuromusculoskeletal conditions .

• Eg back pain, neck pain, trigger points

• Pain management

Contraindications

• Direct irradiation of the eyes

• Malignancy

• Ares recently exposed to radiotherapy

• Haemorrhaging Regions

Precautions

• Low back or abdomen during pregnancy

• Epiphyseal plates in children

• Impaired sensation or mentation

Parameters for the use of lasers

• Type of diode

• Wavelength

• Power

• Energy density

Type of Diode• LED – light emitting diode- semiconductor diode

that produces low power light in a range of frequencies

• SLD- supraluminous diode- semiconductor that produces high power light in a narrow frequency range

• Laser diode – semiconductor diode and optics that produce laser light

Wavelength

• Laser light applicators produce/output light in the visible or near visible wavelength range of the electromagnetic spectrum

• IR (700 – 1100nm)- longer wavelength and penetrates deeper tissue up to 30 to 40 mm

• Red light(600 -900nm)- short wavelength and suitable for treating superficial tissue at a depth of 5- 10mm

Power

• Light applicator is measured in milliwatts

• Laser for therapy are power more than 5mW and less than 500mW

• Low power light applicators require more time to deliver the same amount of energy as high power light applicators

Energy Density

• Lower energy density recommended for acute and superficial conditions

• High energy density recommended for chronic and deeper conditions

Documentation

• Type of Diode- LD, LED,LED ?• Wavelength (nm)• Power (mV)• Area of body to be treated• Energy Density

Suggested readings

• Physical Agents in Rehabilitation by Michelle Cameron

• Therapeutic Modalities in Rehabilitation by William E.Prentice