The binocular 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.
Indirect ophthalmoscopes use halogen bulbs as the light source although many newer models use LED light sources which operate much cooler and last much longer. The newer models may incorporate battery packs that can be worn on the examiner's belt or can even be incorporated into the headband itself. These make it possible to use the indirect ophthalmoscope without the movement restrictions caused by power cables.
The journey of developing ophthalmoscopy began with an idea by the great physicist, Hermann von Helmholtz, who described the optical principles of direct ophthalmoscopy in 1851 .This was followed by series of innovations and methods of examination including the indirect method of ophthalmoscopy developed by Reute in 1852, binocular model by Marc-Antoine Giraud-Teulon and more practical hand-held reflex-free binocular ophthalmoscope by Allvar Gullstrand. It was Charles Schepens who popularised indirect binocular ophthalmoscope.
Reunión virtual con el Dr. Julian Triviño (Colombia)