A hand-held vision card may be substituted for the Snellen chart at the bedside. These cards are also used to test near vision. Diopters are used to measure the power of a lens. The line of hairs in the external ear is a good approximation of where the bony canal begins. Inserting the speculum beyond this point can be very painful.
Insufflation means to change the pressure in the outer ear.
The tympanic membrane normally moves easily in response to this pressure change. Lack of movement is a sign of negative pressure or fluid in the middle ear. Bates refers to this procedure as pneumatic otoscopy.