Otoscopic examination cannot be performed successfully unless the examiner's eyes can focus sharply on the structures examined with the otoscope.
With advancing age (usually starting around the fourth decade ), the eyes lose their ability to accommodate and become farsighted due to a combination of ciliary muscle weakness and a loss of elasticity in the crystalline lens of the eye.
The presbyopic otoscopist may find some difficulty in bringing the tympanic membrane sharply into focus when viewing through the otoscope.
This problem can usually be resolved by varying the length of the speculum used or by wearing corrective eyeglasses. It is hoped that in the future, some farsighted manufacturer will provide corrective lenses (ranging in power from + 3 to ‑ 3 dioptres) that can either be clipped on to the back of the otoscope or inserted in place of the standard magnifying lens (the standard lens varies from + 9 to +11 dioptres) provided with the otoscope.