Understanding and caring for an indirect ophthalmoscope

or indirect ophthalmoscope, is an optical instrument worn on the examiner’s head, and sometimes attached to spectacles, that is used to inspect the fundus or back of the eye. It produces an stereoscopic image with between 2x and 5x magnification. It is valuable for diagnosis and treatment of retinal tears, holes, and detachments. The pupils must be fully dilated for it to work well. In a dark room, the examiner orientates his/her head so that light from the internal light source is directed into the patient’s eye. A positive-powered condensing lens is held by the examiner at its focal length from the patient’s eye, serving two purposes (Figure 1):