Light Modalities
Chapter 19
Description
Light modalities are found on the electromagnetic spectrum Most abundant form of
energy in the universe
Drying superficial tissues or via superficial photochemical effects
Some mild superficial thermal effects
Types of Therapeutic Lamps
Infrared Superficial dry heat
Ultraviolet Heats the body’s tissues for either tissue
destruction or therapeutic effects Laser
Combination of homogenous ultraviolet and/or infrared energy
Infrared Lamp
Used to dry seeping open wounds or sedate superficial sensory nerves
Radiant modality: An electrical current passes through a carbon or tungsten filament Intensity controlled by adjusting current flow or distance
between lamp and tissue Constant temperature, increased risk of burns Heating skin depends on the amount of radiation absorbed
Pigmented, darker skin will absorb more energy and will heat more rapidly than lighter skin
Types of Infrared Lamps
Near-Infrared Luminous Infrared Lamp Wavelength: 780 to 1,500 nm (near visible light) Thermal Effects: 5 to 10 mm deep Energy formed by carbon and tungsten filament
Light bulb Some energy is reflected by the surface of the skin
Types of Infrared Lamps
Far-Infrared Nonluminous Infrared
Radiation Wavelength: 1,500 to
12,500 nm Thermal Effects: < 2mm
Less penetrating than Near-Infrared Skin feels warmer
Energy formed by metal coil i.e. electric stove or space
heater Invisible to human eye
Effects of Infrared Lamps
Constant, dry heat to assist with superficial tissue Dermatological conditions Increase cell metabolism Blood flow Muscle Relaxation
Contraindications Any conditions in which other forms of
superficial heat are contraindicated
Clinical Application
Turn On and warm if necessary Treatment Duration: 20 to 30 minutes Intensity: adjust wattage or distance of lamp
Luminous = 24 inches Nonluminous = 32 inches Inverse Square Law Cosine Law
Clean sweat and dirt, remove jewelry, and fit infrared goggles (if applicable) for patient
Ultraviolet Therapy
Used to produce photochemical reactions in the skin
Wavelength: 180 to 400 nm 3 UV bands (A, B, and C) produce unique
effects
Ultraviolet A & B Lamp Ultraviolet C Lamp
Types of UV UV-A
AKA: near UV Effect:
Erythema without pigmentation UV-B
AKA: middle UV Effects:
Erythema without pigmentation Formation of vitamin D Skin tanning (blister/burn)
UV-C AKA: far UV Effects:
Kills bacteria Formation of vitamin D Skin tanning
Types of UV Lamps
‘Hot’ UV Lamps Low Volt (30-110V) High-Amp (5A) Electrical current passes through tube, argon gas
heats, vaporizing and polarizing mercury to produce UV light in ALL 3 bands and visible violet light
‘Cold’ UV Lamps High Volt (3000V) Low-Amp (15mA) Energy is cooler than ‘Hot’ and produce UV-C
Biophysical Effects
Energy absorbed at a depth between 0.20 to 0.22 mm
Damages cell proteins, DNA, & RNA to initiate local inflammatory responses
Effects: Vitamin D synthesis Enhances melanin production Thickens epidermis Superficial vasodilatation Bactericide
Effects of UV Lamps
Wound Healing Activates inflammatory response Use: Cold Lamps at intensity of E3
Treat Skin Disorders i.e. psoriasis Exfoliates tissue and damage DNA that produces
the excess skin growth associated with psoriasis Use: UV-B
UV Contraindications
Sunlight sensitivity Fair skin (precaution) Medications or food that increase sunlight
sensitivity Examples:
Tetracycline Shellfish
Hyperthyroidism
UV Dosage
Determined by Minimal Erythema Dose Least amount of UV exposure time to produce
redness within 1-6 hrs and disappear within 24 hours “Hot” Lamps
Determined by each patient and each lamp Standard distance = 30 in., not closer than 15 in.
“Cold” Lamps Standard MED value 12-15 seconds at a distance = 1 in.
Determining MED for UV Lamp
Cardboard Test Strips 1. 6 different shapes cut
out 2. Use to cover shapes
UV Lamp 30 in. away
MED (Cont.)
Expose 1 cut out, open the shutters for 30- sec., expose the 2nd cut out and leave the 1st uncover for the 30-sec.
Repeat the steps above for the remaining 4 cut outs, but expose them at 15-sec intervals
Instruct patient to check area every hour and record changes
UV Treatment Dosage SED
No erythema MED
Smallest dose that produces erythema within 1-6 hr E1
Erythema lasts for 1-3 days, some scaling of skin present, approximately 2.5x MED
E2 Erythema with edema, peeling, and pigmentation, approximately
5x MED E3
Severe erythema and burning, blistering, peeling, edema, approximately, 10x MED
Clinical Application
Calculate treatment dose and duration Clean area and remove jewelry Cover skin not being treated (sunscreen if
applicable) Fit UV-resistant goggles to patient and clinician Position lamp at right angle using the correct
distance and duration for each type of lamp Clean machine and check periodically for
maintenance of bulbs
Adjusting the Treatment Dose
Biophysical changes occur with light exposure causing changes in treatment
Duration 30 to 50% increase for each subsequent
treatment If 3 to 5 minutes, then distance is reduced 5 to 10 sec is decreased when missing a
treatment Be aware of patients skin color and the lamps
distance, duration, and angle
Therapeutic Lasers
L=Light A=Amplification by S=Stimulated E=Emission of R=Radiation Classified by the FDA’s Center for Devices
and Radiological Health
Types of Lasers High-Power Laser
“Hot Laser” Effect:
Causes thermal changes in tissues (cause tissues to be destroyed, evaporated, or dehydrated)
Uses: Surgery Capsular shrinkage Wrinkle and tattoo removal
Low-Power Laser “Cold Laser” Effect
Causes photochemical changes in tissue Uses:
Wound healing Arthritis Burn care
Production of Laser Energy
Lasers are referred to by the type of active medium (gas, liquid, solid) HeNe: visible red light penetrating 0.8 to 15mm GaAs: invisible penetrating up to 2 cm
Energy is introduced into the active medium An orbiting electron briefly elevates into a
higher or ‘excited’ state The electron spontaneously returns and
releases another photon
Effects of Lasers
Photons are absorbed by tissues to alter molecular-level activity
Theorized to affect pain-producing tissue (muscle spasm), by increasing ATP synthesis that increases cell metabolism and encourages the release of free radicals
Wound Healing
Superficial wounds Ulcers, surgical insicison, burns
Lasers alter cell membrane permeability and increase in fibroblast, lymphocyte, and macrophage activity occurs
Blood and lymph improve to promote the growth of granulation tissue
Increase collagen and tensile strength of healing wounds
Pain Reduction
Decrease acute and chronic pain Reduce the rate and velocity of sensory
nerve impulses Similar to cryotherapy but without thermal
changes
Fracture Healing
May enhance fracture healing and bone remodeling by increasing capillary formation, calcium deposition, increase callus formation, and reducing hematomas
Photons striking the tissue create acoustic waves that affect bone healing similar to ultrasonic bone growth stimulators
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