An otoscope is a tool that allows a doctor to see inside an ear. To accomplish this, the otoscope needs to hold the ear canal open, and the speculum attachment on the end of the otoscope performs this function, typically as a plastic cone-like object strong enough to stretch the muscles of the ear canal open. Otoscope specula can be disposable or they can be reusable once sterilized.
The human ear canal is a hollow tube that twists slightly inside the head. Various medical problems can affect the ear, from the temporary deafness caused by impacted ear wax, to burst eardrums and ear infections. To diagnose the exact problem affecting the ear, a doctor generally inserts an otoscope into the ear. This is a magnifying tool with a light source, as the inside of the ear canal does not let in much light, and the otoscope body itself blocks natural light from illuminating the canal.
At the front of the otoscope is the speculum, also called the cone, from its appearance. The narrowest end is inserted into the ear, and the portion that remains outside is larger, so it does not accidentally get stuck inside the canal. A typical adult ear canal is about 0.8 inches (2 cm) in length, and otoscope specula help keep the walls of the canal apart so the doctor can see deep inside the ear. Only the speculum part of the otoscope is typically inserted into the ear, and the doctor holds the body of the otoscope outside of the body.
Otoscope specula come in a variety of diameters, to fit a variety of ears. This is necessary because children, for example, have smaller ear canals than adults. A too-large speculum could cause pain, whereas a speculum that was too small could be useless for holding the ear canal open. A typical range of diameters for otoscope specula is from about 0.1 to 0.2 inches (3 to 5mm).
Commonly, otoscope specula are made of plastic, due to its practicality to clean and its resistance to breakage. Sometimes an otoscope has a speculum on the end that can be removed after use on one particular patient for cleaning and sterilization, before being used on another patient. Alternatively, a doctor may choose to use disposable specula, which can be thrown away after one use and replaced with a new speculum.