The examiner should always be aware that the perceived colour of the ear canal and tympanic membrane will vary according to the type of light source used.
A new series of norms must be learned if changing from incandescent to halogen light or vice versa.
The colours observed when using an otoscope equipped with a halogen light resemble those seen when the ear is illuminated with a head mirror reflecting sunshine or bright northern daylight (see Chapter 1).
The fibreoptic transmission or distribution of light provides a 360' ring of light without visual obstruction or reflections from the interior of the speculum. Those otoscopes which are illuminated by an incandescent bulb utilize a 2.5 V power supply. Those modern otoscopes which are illuminated by the brighter quartz halogen light bulbs require a 3.5 V power supply.
3.5 V halogen fibreoptic pneumatic otoscope and throat illuminator (Welch Allyn 20 000) with rechargeable battery handle (Welch Allyn 71 000).