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| About Phototherapy |
| Phototherapy |
Phototherapy is the treatment procedure where skin diseases are
treated with light. It can be divided into two main modalities.
The first is irradiation with UV-A (320 to 400 nm) after
ingestion or application of photosensitizers called psoralens.
The mix of photosensitizer plus light is called PUVA. The second
is irradiation with UV-B (290 to 320 nm). UV-B light is produced
by the sun, fluorescent lamps, short arc lamps with UV enhanced
filtering, and lasers. Depending upon the shape of the spectrum
of light emitted by the source, UV-B can be broadband (290 to
320 nm), narrow band (310-315 nm) or monochromatic (308 nm from
the excimer laser). Light is delivered either directly from the
source in the case of fluorescent tubes or the sun, or via wands
when systems use light concentrators and filters.
There is debate on the relative efficacy and adverse effects of
both modalities. PUVA generally clears psoriasis faster but
long-term toxicity to the skin is greater. Some patients cannot
tolerate therapeutic PUVA doses. UV-B clears psoriasis in
approximately 80% of patients without the need of
photosensitizers. Narrow band or monochromatic UV-B allows
higher doses and thus fewer treatments.
The initial therapeutic dose approximates the minimal erythema
dose or MED. The MED is the least light exposure causing a
sunburn reaction and increases progressively with subsequent
treatments as the skin becomes more tolerant of UV irradiation.
Therapeutic protocols involve two to five sessions per week.
Generally, the disease clears in 15-35 treatments. After the
condition clears, maintenance sessions are less frequent,
typically once a week. In most people, psoriasis involves small
areas of the body. If phototherapy can be targeted only to
affected skin in a manner that normal skin is not exposed to
light, the patient can tolerate energy significantly exceeding
the MED. This approach results in fewer treatments and faster
clearance.
When the whole body is affected, patients can utilize a UV-B
treatment process similar to a conventional full-body tanning
booth. If the affected area is small, hand wands or fiberoptic
light sources that concentrate the light can be used. Several
devices available today attempt to treat scalp psoriasis, but
they are ineffective because they utilize a light source
designed for other body parts, such as the hands or elbows,
where psoriasis is often localized. Some are sold with a
comb-type attachment designed to separate the hair and deliver
light to the exposed psoriatic scalp. Interviews with doctors
and patients indicate that these devices are neither efficient
nor easy to use. The treatment is inconsistent and
time-consuming. Hair blocks light from reaching the skin, and
only a small area of the psoriatic scalp can be exposed and
treated with each use. In the meantime, skin on the neck,
forehead and ears is exposed and may be burned.
In the past few years, new spot treatment devices based on short
arc lamps with UV-enhanced filling and filters have been
introduced. These devices produce an intense spot of UV light
less than an inch square. The energy needed for treatment is
delivered in a fraction of a second or up to a few seconds if
the dose is high. The affected area is covered by tiling the
spots one next to the other. The excimer laser performs the same
function, producing light with a laser instead of a lamp. |
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Principles of Ultraviolet Phototherapy |
Ultraviolet Light B (UVB) Phototherapy - involves exposing the
skin to light of a particular spectrum of the ultraviolet band,
called UVB. This area is defined as 290 to 320 nanometers.
Exposure to this part of the spectrum has been proven beneficial
for the control of skin conditions listed in the indications for
use. For details on phototherapy and how it is benefiting these
skin conditions the user should consult medical literature and
experts in the field.
Regarding the rules for determining the dosimetry for UVB
phototherapy, the following principles apply: |
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The skin needs a
certain amount of energy (Joules/cm-square) for
the condition to subside. |
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In an ideal
situation, this energy could be delivered in a
single treatment. |
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UVB light
exposure at each treatment is limited by the
susceptibility of skin to sunburn and the
patient’s ability to tolerate exposure in the
involved areas. |
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As a general
rule, the UVB light exposure per treatment
should not exceed the Minimum Erythema Dose
(MED). This dose is the lowest exposure to
ultraviolet light required to produce erythema.
Erythema is the slight redness of the skin, a
type of sunburn reaction. In certain parts of
the body and if the involved area is small, the
patient can tolerate a dose higher that the MED. |
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Treatment can
resume when the skin reaction to ultraviolet
light has subsided, usually 48 hours after
exposure. |
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With each
treatment, exposure to ultraviolet light
produces skin melanogenesis (tanning of the
skin). Tanning increases skin tolerance to
ultraviolet light permitting an increase to
exposure in subsequent treatments. |
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Treatment is
repeated until the condition falls into
remission. |
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Some of the skin
diseases come and go. To keep the disease in
permanent remission maintenance treatments at
regular intervals are recommended. |
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The UVB part of the spectrum has been chosen because the
contrast between therapeutic effect and erythemogenesis is the
highest. The shorter wavelengths that define the UVC region
(100-290 nm) have increased phototoxic effects. The longer
wavelengths that define the UVA region (320-400 nm) have
diminished therapeutic effects, requiring at least a
thousand-fold higher dose to produce therapeutic results. The
effectiveness of light in the UVA region can be improved if
combined with certain photo-sensitizers. In recent years, the
trend in phototherapy is to use UVB and avoid the combination of
UVA and photo-sensitizers because they cause undesired side
effects in some individuals.
Scalp Phototherapy Procedure
To treat the scalp, light is applied to it with the
LiteBrush™. The dose is calculated by the physician and the exposure
time and output intensity are adjusted. The scalp area is
divided into strips and one strip should be treated at a time. A
pen can be used if necessary to mark the borders of each strip.
If there is little scalp involvement with few affected areas,
only the affected areas can be treated, one at a time. If the
affected area is widespread, the whole scalp should be treated.
The Fiberoptic Brush is positioned over the affected area. Light
is delivered to the scalp with a slow, gentle, steady combing
action at a rate of approximately 1-2 cm/second. All
adjacent strips are exposed until all sites involving psoriasis
on the scalp have been treated.
Note: Each Brush is to be used by a single patient only.
Spot Treatment Procedure
When small areas of the body are involved, spot treatment is
recommended instead of whole body treatment. The dose is
calculated by the physician and the exposure time and output
intensity are adjusted. The handpiece is placed over the area to
be treated and the energy is delivered to each spot. For large
areas, the adjacent spot or area is treated until the entire
area has been treated. Treatment is complete when the area to be
treated is completely covered with irradiated spots. |
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Phototherapy Contraindications and Precautions
As with natural sunlight, overexposure to UVB can cause eye and
skin injury, and allergic reactions. Repeated exposure may cause
premature aging of the skin and skin cancer.
Some patients have a history of skin problems or sensitivity to
light. Certain medications and cosmetics contain substances that
may increase skin sensitivity to Ultraviolet radiation.
The physician responsible for phototherapy must screen and
evaluate all patients prior to UVB phototherapy treatments and
monitor them for complications during and after the treatments.
The following patient types should not be treated with this
device unless the physician responsible considers phototherapy
necessary and safe. |
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Individuals with
light sensitive disease, including, but not
limited to, Porphyria or Lupus Erythematosis. |
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Individuals with
a current or past history of a Melanoma. |
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Individuals with
Invasive Squamous Cell Carcinoma or past history
of Invasive Squamous Cell Carcinoma. |
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Individuals with
aphakia, because of the significantly increased
risk of retinal damage due to the absence of
lenses. |
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Females who are,
or suspect that they may be Pregnant. |
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Patients
exhibiting Multiple Basal Cell Carcinoma or
having a history of Basal Cell Carcinoma should
be carefully observed during and after
treatment. |
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Patients having a
history of previous X-ray therapy or Grenz-ray
therapy should be carefully observed for signs
of Carcinoma. |
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Patients having a
history of previous Arsenic Therapy should be
carefully observed for signs of Carcinoma. |
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Special care
should apply in treating patients who are
receiving parallel therapy with known
photosensitizing agents such as, but not limited
to: ACE inhibitors, Non-steroidal Anti-inflammatories,
Amiodarone, Phenothiazines, Ciprofloxacin,
Protriptyline, Nalidic Acid, Sulfonamides,
Tetracyclines, Nifedipine, Thiazides, Coal Tar
or Plant-derived Psoralens, Griseofulvin,
Halogenated Salicylanilides (bacteriostatic
soaps), certain organic staining dyes (Methylene
Blue, Toulidine Blue, Rose Bengal, and Methyl
Orange) and some dietary supplements believed to
act as photosensitizing agents. |
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About Phototherapy