Ultraviolet Therapy

Original Editor - Grace Barla

Top Contributors - Niha Mulla, Grace Barla, Sai Kripa and Kim Jackson  

Introduction

Ultraviolet  therapy  is a form of treatment commonly used to treat certain skin disorders. It consists of irradiation of the patient with the UVA band of ultraviolet light. The therapeutic application of ultraviolet (UV) portion of the electromagnetic spectrum (or UV therapy) has been used for decades, although the recognition of the therapeutic effect of sunlight, dates back to ancient times, artificial UV radiation that allows precise dosing has only been available since last century with UV-A in 1974, narrowband UV-B in 1984, UV-AB in 1985, and UV-A1 in 1992.

Ultraviolet therapy has been reported to be very effective in destroying bacteria and promoting wound healing and therefore a promising adjunctive therapy for chronic wounds infected with resistant bacteria.

Ultraviolet therapy is commonly used to treat conditions like, psoriasis, atopic dermatitis, vitiligo, mycosis fungoides, and hand/feet eczema.

Though there is evidence present for effectiveness of Ultraviolet therapy in the management of wounds and other skin conditions and the significant role physiotherapists play in its application, anecdotal evidence suggests that this modality is not routinely applied for treatment in regular clinical practice.

Description

Ultraviolet Radiation (UVR) is a non-ionizing radiation that lies between soft x-rays and visible light in the electromagnetic spectrum. It has a wavelength of 100 nm to 300/480 nm. The therapeutic part of ultraviolet spectrum are classified by International Commission on Radiation (CIE).

Ultraviolet radiation obeys the law that governs all the radiations, they may reflect, scatter and are absorbed by molecular chromophores. The degree of absorption is generally greater for shorter wavelengths, shorter wavelengths penetrate less deeply. Absorption depends on the thickness of the epidermis and any pigmentation of the skin. Skin thickening due to lesions will result in increased scattering and absorption and thus reduced penetration.

Types of ultraviolet radiations

On the basis of dominant biological effects displayed by each region as :

UV - A 315 - 400 nm Encourage wound healing

UV - B 280 - 315 nm Skin erythematous region

UV - C 100 - 280 nm Germicidal region

Production of ultraviolet radiation

The sun emits broad spectrum of ultraviolet radiation, including UV-A, UV-B, UV-C. Both UV-A and UV-B reach the earth from the sun. However, UV-C is filtered out by the ozone layer.

For therapeutic purposes, some form of generator is used to emit ultraviolet radiation

Types of UVR Generators:

1. Mercury vapor lamp: It is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. These are used for the production of ultraviolet rays for therapeutic purposes. There are two types of mercury vapor lamp:
   • Air cooled medium pressure mercury vapor (Alpene sun lamp) : It is a U-shaped glass tube filled with argon gas at low pressure. A small amount of mercury is enclosed in the tube. The tube is sealed at both ends. Burner is made up of quartz as this material allows passage of UVR and can withstand very high temperature. At the end of glass tubes, electrodes are placed in metal caps. Step up transformer is used to apply high potential difference i.e 400V across two metal caps. Step up transformer (400V) used to apply high potential difference across the two metal caps. There occurs ionization of Argon gas that promote movement of positive ions and free electrons which constitute current flow across the tube. Electrons move towards (+) electrode, positive ions move towards (-) electrode and collision between moving ions and neutral argon causes further ionization of neutral argon gas (produce UVR). Flow of current across the tube produces heat making vaporization of liquid mercury (Hg). Hg vapor gets ionized by flow of current causing further acceleration of flow of current. UVR produced by the process of – -Ar Ionization -Hg Vaporization -Hg Ionization •This process takes about 5mins for the emission of ultraviolet after the burner is started. •When lamp is turned off, ions of Ar and Hg recombine so that within the tube everything returns to its neutral state.
   • Water cooled mercury vapor lamp (kromayer lamp) : It is a water cooled UV lamp which eliminate the danger of burn and absorb IR. The lamp is surrounded by circulating distilled water to absorb IR. A pump and a cooling fan are organized into body of lamp to cool water. After using, water circulation should be continued for 5 minutes and then burner is switched off to cool lamp. At the front of lamp’s head, water is circulated between two quartz window, which allows UV to emerge. Advantage- direct contact method- (safe as circulating water absorb IR).

1. Fluorescent lamps: One major problem with the mercury lamp is that it produces a certain proportion of short ultra-violet rays and modern treatment regimen requires the use of long-wave ultra-violet without the short wave to avoid side effects, hence various types of fluorescent tubes have been designed. Each fluorescent tube is about 120 cm long and made of a type of glass that allows long-wave ultra-violet to pass. The inside of the tube is coated with a special phosphor and the spectrum of each fluorescent tube depends on the type of phosphor coating. Here, if any short ultraviolet radiation is produced it is absorbed by the phosphor and is re-emitted at a longer wavelength. Depending upon which particular phosphor is used,  the output of the tube may be part UVB and part UV-A  or UV-A, as in the PUVA apparatus, but accurate control of the emitted wavelength is possible.
2. Theraktin tunnel: The theraktin tunnel is a semi-cylindrical lamp, which has four Fluorescent lamps mounted inside it, with each tube being mounted in its own reflector, in a way that even radiation is produced to allow treatment of whole body to evenly occur in two halves.
3. PUVA apparatus: It is usually used for treatment of psoriasis, where a large amount of UVA, is required. The tubes in PUVA are usually mounted in a vertical battery on a wall, or four sides of a box surrounding the patient. This form of ultra-violet radiation is usually given two hours after the patient has taken a photoactive drug such as psoralen: hence the term PUVA (psoralen ultraviolet A)

Dosage of ultraviolet radiation therapy

Dosage of ultraviolet radiation therapy depends on number of factors like; distance between lamp and the skin, angle at what the radiation touches the skin and the time for which skin is exposed to the radiation.

Degree of erythema post ultraviolet therapy is the deciding factor of the dose;

1. Dose E1 - causes mild pink appearance of the skin which lasts for up to 24 hours with no presence of skin edema or discomfort. E1 is also called as MED - Minimal erythema dose. It is the smallest dose of ultraviolet radiation to result in erythema that is just detectable by eye.
2. Dose E2 - is 2.5% of E1 and causes definite milk red appearance of the skin that blanches on pressure which lasts for up to 2 days with no edema but slight soreness and irritation of the skin and powdery skin desquamation.
3. Dose E3 - is 5% of E1 and causes very red skin appearance with no blanch of skin on application of pressure, it lasts for 3 to 5 days. Post dosage some some edema is present at the area of application, also the application area feels hot and painful with thin sheet like desquamation of skin.
4. Dose E4 - which is 10% of E1 and leads to angry red appearance of the skin which lasts for a week. It also leads to formation of blisters on the skin which is very painful. It also causes thick sheet like desquamation of skin.

Calculation of dosage:

• E1 is determined from the skin test and the other erythemal doses are calculated as follows:
• Suberythemal  - 75% of E1
• E2 = 2.5×E1
• E3 = 5×E1
• E4 = 10×E1
• Double E4 = 20×E1
• E4 and double E4 are used on an open wound

Physiological effects of ultraviolet radiation therapy

1. Erythema because of dilation of the capillaries and arterioles.
2. Pigmentation or tanning of the skin
3. Desquamation or Increased skin growth
4. UVB can convert sterols in the skin   to vitamin D, therefore increasing the production of vitamin D in the body.
5. Prophylactic effect starts in the body as the resistance of the body to infection is increased because of the stimulation of reticuloendothelial system.
6. Ultraviolet radiation destroys Langerhan’s cell and stimulates the proliferation of suppressor T cells, these immunosuppressive effects may contribute to the development of skin cancer.
7. Strong dose of UVB and C radiation to the eyes can lead to conjunctivitis and photokeratitis which in turn results in Irritation of the eye, a feeling of grit in the eye, watering of the eye and aversion to light. (photophobia). A strong dose of UVA may also lead to the formation of cataracts.
8. Prolonged exposure of UVR lead to, premature ageing of the skin, this is especially so in the light -skinned people. It also decreases function of sebaceous and sweat glands. The skin becomes wrinkled, dry and leathery.
9. Cancer: Carcinogenesis is a danger, as these rays may influence the DNA and thus effect cell replication. Squamous cell carcinomas are a serious side effect. Hence, Shorter ultraviolet waves should be avoided, and course of treatment should not exceed four weeks.

Therapeutic use of ultraviolet radiation therapy

• Psoriasis
• Acne vulgaris
• Eczema
• Chronic infection
• Vitiligo
• Treatment of vitamin D deficiency
• Pruritus

Contraindications of Ultraviolet radiation therapy

• Irradiation of the eyes
• Skin cancer
• Pulmonary tuberculosis
• Cardiac, kidney and liver disease
• Systemic lupus erythematosus
• Fever

Danger of Ultraviolet therapy

• Burn
• Premature skin aging
• Carcinogenesis
• Damage to eyes
• over dose of ultraviolet therapy
• Shock