A Wood’s lamp examination is a test that uses ultraviolet (UV) light to look at the skin closely. 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.
What is a Wood’s Lamp?
Wood’s 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.
How Wood’s Lamp is used to detect Vitilio?
– Wood’s Lamp examination is carried out in absolute darkness. There should either be no windows in that room, or they need to be covered very heavily.
– The lamp is warmed up before the examination and 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.
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 wood’s 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.
Wood’s 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.