warts around the nail unit are commonly caused by human papillomavirus  1 , 2 and 4 . periungual warts originate from the skin possessing granular layer including hyponychium , proximal and lateral nail folds . the current management options for periungual warts include topical , intra - lesional and systemic drugs , lasers and surgical procedures . the choice of a procedure in a patient depends on skill of the treating physician , location and extent of wart , number of warts , duration of warts , age and immunologic status of the patient . nevertheless , periungual warts are known to recur and one of the most common causes of recurrence is inability of treating physician to determine the extent of it . the device is handy with dimensions of 8.5 cm  5.5 cm  2.5 cm [ figure 1a ] . power source for the light emitting diode ( led ) device is a 9v battery with a switch adjacent , both fixed at the upper part of the device [ figure 1b ] . a row of nine 3.3v , 20 ma red colour leds is fixed on a plastic board and is enclosed in a black opaque cover [ figure 1c ] . the opaque cover transmits light only to the bottom and there is no dispersion of light through the sides [ figure 1d ] . the total cost incurred to design the device is 200 inr [ table 1 ] . ( a ) finger - shaped red light emitting diode device ; side view : battery on top , ( b ) top view : 9v battery power source with a switch adjacent , ( c ) bottom view : row of nine light emitting diodes on a plastic board , ( d ) opaque black cover allows light to pass only through bottom cost of making the device visible spectrum has a colour range from violet to red , with a wavelength ranging from 400 to 700 nm . blue light has a wavelength range of 400470 nm and can penetrate only up to 1 mm . red has the longest wavelength ( 630700 nm ) in the visible spectrum and can penetrate 16 mm [ figure 2 ] . wavelength of light and depth of penetration : across the visible spectrum from violet to red , the light penetrates deeper with higher wavelengths the led device fits snugly when placed with its bottom on the finger [ figure 3 ] . as there is no dispersion of light through the sides , when illuminated , the red light passes onto the finger . wart stands out contrasting as black against a bright red background making it easy for the treating physician to appreciate its extent [ figure 4 ] . limitations of white light are it is ineffective in thicker palmoplantar skin and darker constitutional skin colour . these limitations could be overcome with this device due to deeper penetrating red light . light emitting diode device fits snugly when placed with its bottom on the finger periungual wart stands out black against a bright red background therapies for periungual wart are targeted only to that portion visible to the naked eye . subungual extension of wart can be missed with the naked eye examination . for subungual extension , most treatment modalities require a partial nail avulsion before targeting therapy except for those having immunomodulatory action like bleomycin . this device addresses this problem of assessment and delineates the complete extent of the periungual wart with distinct advantages [ table 2 ] . advantages of the device the red led device can also be used in injecting sclerotherapy agents for varicose veins and drawing blood in individuals with clinically invisible veins . knowing the extent of periungual wart is required for successful management of the condition which can be achieved with this led device .
management of periungual wart is a great challenge , especially when there is subungual extension . 
 the major cause of recurrence of wart is improper clinical assessment of its extent and not directing therapy against the entire wart . 
 this difficulty of ascertaining its extent could be overcome with this finger - shaped red light emitting diode device . 
 red light in the device penetrates the thick palmar skin and dark constitutive skin colour due to its longer wavelength .