Home therapy is rare in North
America, because, understandably, many dermatologists
are reluctant to prescribe a treatment that is difficult
to monitor and that has potential risks. Generally,
only those who live far from treatment centers use home
phototherapy. In addition, home phototherapy units are
quite expensive.
Narrow-band
Ultraviolet B Therapy
Also known as selective UVB phototherapy,
narrow-band ultraviolet B (NB-UVB) light therapy is
a newer phototherapy method that can offer safer and
more effective results in the treatment of psoriasis.
Ultraviolet B ranges from 290-320 nm in wavelength.
Special narrow-band UVB lamps emit a very narrow band
of high intensity light at 311-312 nm wavelengths.
The major advantage of this therapy
is that it eliminates much of the high-energy, shorter
ultraviolet B wavelengths that have been attributed
to burning, premature aging and increasing the risk
of skin cancers. Initial research has found that narrow-band
ultraviolet B is more effective and can keep the psoriasis
clear for longer, even after the therapy is discontinued.
Recent studies show that in some patients, narrow-band
ultraviolet B provides faster clearance with fewer treatments.
For most, approximately 30 to 35 treatments could be
required to obtain clearance; however, for some, it
could be fewer.
Narrow-band ultraviolet B can
also be used in combination with topical treatments
such as corticosteroids, calcipotriol, anthralin, tar
and tazarotene gel to improve psoriasis.
Psoralen
Ultraviolet A Light Therapy
When used alone, ultraviolet A
is only minimally effective in treating psoriasis. However,
when combined with topical application or ingestion
of psoralen, ultraviolet A can have a significantly
greater effect in clearing psoriasis. Psoralen plus
ultraviolet A (PUVA) involves administration of psoralen
prior to exposing skin to ultraviolet A light. Psoralen
makes the skin more sensitive to the effect of ultraviolet
light, and as a result improves the effect of ultraviolet
A in the treatment of psoriasis.
Drs. Parish, Fitzpatrick and colleagues
at Harvard Medical School first reported the use of
PUVA in 1974. In their initial clinical experiment,
a patient ingested psoralen, then half the body was
covered and the patient received ultraviolet A on the
opposite side. The patient showed clearance of psoriasis
on the side that received the combination, but no improvement
on the side that was protected from UVA. This indicated
that the combination of psoralen and ultraviolet A was
essential for obtaining the beneficial effect.
After taking psoralen, you need
to wear protective sunglasses for 24 hours, because
there is a possible risk of developing cataracts (abnormalities
in the lens of the eye, causing blurry vision or decreased
vision). To date, an increase of cataracts has not been
reported in PUVA patients treated with careful eye protection.
Certain patients should
not have PUVA therapy, such as those with medical conditions
that make them more sensitive to the sun (e.g., systemic
lupus erythematous). Also, if you are unable to stand
for long periods of time, are pregnant or are unable
to comply with treatment, you should not use PUVA.
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