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Wood's lamp
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Woods light can be used to detect vitiligo at a very early stage for preemptive treatment. It can similarly be used for an early assessment of the success of treatment. This article explains the working of wood’s lamp and its use.
Woods lamp is a simple and safe device which emits Ultraviolet rays in the wavelength range of 320 and 400 nm with a peak at 365 nm. This light is invisible to the human eye. It was invented by Robert W. Wood, a physicist from Baltimore in 1903.It is being used in dermatology since 1925, and examination under woods light can be useful in the diagnosis of many skin conditions like infections, and pigmentary disorders like vitiligo. It has recently been found to be helpful even in the diagnosis of certain skin cancers.
Principle
Certain tissues of the human body can absorb the woods light and then emit a light which is visible to human eye (fluorescence). This light is however so faint that it can only be seen when examined in a darkened room and the observer is dark adapted. The tissue hence appears bright in the darkened room.
Light emission from normal skin is very faint or absent. But diseased skin may start emitting visible light, and the appearance of such emitted light is usually different in different disease, which can be very helpful in diagnosis of such diseases.
Technique
Woods lamp is very simple to use in the skill technique can be learnt very easily. Here are a few basic things to know about it
- Woods Lamp examination must be carried out in absolute darkness. There should either be no windows in that room, or they need to be covered very heavily.
- The lamp needs to be warmed up before the examination and should be switched on at least 1 minute before examination
- The examiner should be dark adapted, which means he / she should have been staying in the dark room for at least 20 minute before the examination. It helps to appreciate the contrast more easily and avoids errors.
- The light should be held 10 to 12 centimeters from the skin
- Medicine, ointments and grease should be wiped from the skin, not washed to prevent false negative interpretation.
Medical Applications of Woods Lamp
Woods light was first used in medicine to help in the diagnosis of fungal infections like Tinea capitis and Pityriasis versicolor, but it has also been found to be helpful in other infectious disorders like, Pseudomonas infections, Erythrasma, and Acne vulgaris. We shall however limit ourselves to the use of woods light for the diagnosis of Vitiligo.
Wood's Light and Vitiligo:
Loss of pigment from the skin is the hallmark of vitiligo which can usually be easily seen by the naked eye in dark skinned people. It may however be very difficult to appreciate in fair skinned people because the difference in color of normal and abnormal skin is hardly any. This is where woods lamp can be very handy. The normal function of melanin is to block and absorb the light. Since there is less or no epidermal melanin in the vitiligo affected patches, it can not block the light emitted from deeper layers of the skin. The vitiligo affected skin appears like window of blue white light with sharp margins. Woods lamp s hence helpful in the diagnosis of vitiligo, especially in the fair skinned people.
Woods light can be used to detect vitiligo at a very early stage for pre-emptive treatment. It can similarly be used for an early assessment of the success of treatment.
Loss of pigment from the skin is the hallmark of vitiligo which can usually be easily seen by the naked eye in dark skinned people. It may however be very difficult to appreciate in fair skinned people because the difference in color of normal and abnormal skin is hardly any. This is where woods lamp can be very handy. The normal function of melanin is to block and absorb the light. Since there is less or no epidermal melanin in the vitiligo affected patches, it can not block the light emitted from deeper layers of the skin. The vitiligo affected skin appears like window of blue white light with sharp margins. Woods lamp s hence helpful in the diagnosis of vitiligo, especially in the fair skinned people.
Woods light can be used to detect vitiligo at a very early stage for pre-emptive treatment. It can similarly be used for an early assessment of the success of treatment.
