The Wood’s lamp was invented by a physicist named Robert Wood. It is also called filtered ultraviolet lamp. It is a light with a wavelength of 320-400nm emitted by a high-pressure mercury lamp through a filter containing nickel hydride. It can be used to detect bacterial or fungal skin infection, and also be used to detect skin pigment irregularities, like white patches on your skin called vitiligo, or corneal abrasions.
As a detection method for clinical application in dermatology, it targets a wide range, such as: acne, tinea capitis, white ringworm, tinea versicolor, erythrasma, tinea axillary; certain pigmented lesions such as chloasma, age spots, coffee spots And so on, there are neurofibromas, skin tumors and so on.
Wood’s lamp is known as the microscope of the skin. When used for acne detection, it can accurately determine the degree of accumulation of Propionibacterium. Propionibacterium acnes can also produce protoporphyrin, which produces brick-red fluorescence when illuminated by a Wood’s lamp. This fluorescence can be detected, especially in the hair follicles of the nasolabial folds.
Working Theory
The Wood’s lamp is a method of checking some skin diseases by using 320nm ~ 400nm long-wave ultraviolet light obtained through a filter glass containing nickel oxide, which will help the diagnosis and treatment of these diseases. Obtain 320-400nm long-wave ultraviolet through the filter containing nickel hydride, and then irradiate the affected area with long-wave ultraviolet. If the melanin decreases, the refractive index is strong and the light color appears; while the melanin increases, the refractive index is weak and the color appears dark.
Wood’s light helps in the diagnosis of pigmented skin diseases (including vitiligo). Clinically, it is sometimes difficult to detect light spots on normal skin, especially fair skin, with the naked eye. Vitiligo can be easily detected with Wood’s light, and can be distinguished from other leukoplakia, especially when hair follicle recoloring begins to appear in the leukoplakia, the initial stage of recoloring is not obvious under natural light, but it can be confirmed by observation with the help of Wood’s light.
The skin lesions of vitiligo under the Wood’s lamp are pure white, in sharp contrast with the surrounding normal skin, with clear boundaries. Depigmented moles, pityriasis white, nodular sclerosis, hypopigmented spots after inflammation, hypopigmented spots of leprosy, etc. are yellow-white or off-white under Wood’s light; tinea versicolor is brown or yellow-white; pale anemic moles white skin lesions cannot be seen.
Method of operation
1. Connect the power cord of the Wood’s lamp to the power supply, and the light will be on after pressing the switch for a few seconds;
2. Check through a magnifying glass in a darker room;
Detection method
1. The patient’s bleaching moles, white pityriasis, nodular sclerosis, hypopigmented spots after inflammation, hypopigmented spots of leprosy, etc. under the Wood’s lamp are yellow-white or off-white tinea versicolor is brown or yellow-white anemic moles Pale white skin lesions cannot be seen.
2. When rubbing or the skin turns red, observe whether the leukoplakia is the same redness, or the leukoplakia is more obvious from the appearance, the latter indicates an anemic mole.
3. Skin sensory inspection, including temperature, pain, and touch. The patient’s sensation is normal, and the leukoplakia area of leprosy often has superficial sensory impairment, including the above-mentioned reduced or even disappeared sensation.
4. The isomorphic reaction of vitiligo, in the normal pigmented skin of the deltoid area of the patient’s shoulder, after routine alcohol disinfection, the scratches with sterilized acne needles are 1 cm in size, and the scratches are checked after 1 month, and the pigment is depigmented. If it is not positive, if there is no pigment change, it is negative. According to the experimental scratches, it can be judged as follows: the skin lesions with positive isomorphism are mostly extended type, and the response to photochemotherapy is poor, and the effect of glucocorticoid therapy is better.
Superiority
1. It does not directly touch the inspection site during the operation. It has the advantages of no pain and infectivity, which is suitable for patients of all ages.
2. The Wood lamp is known as the microscope of the skin, which can accurately detect the loss of melanin, distinguish whether it is complete or incomplete vitiligo, and screen out the lesions that have occurred that are invisible to the naked eye.
3. Wood lamp makes the diagnosis of vitiligo easier. The diagnosis process of Wood lamp does not take blood and is painless, and the test results are fast and accurate.
