Keeler Vantage Plus Indirect Ophthalmoscope Features high-contrast optics and advanced engineering with convertible light source with your choice of LED or traditional Xenon bulb. Features Keeler has designed a unique one step movement to make your examinations easier and faster. The (IOS) mechanism (patent pending) means that when you select the small, medium or large aperture, the optics automatically adjust, providing 3 dimensional stereoscopic views of the retina through all pupil sizes. Adjustable illumination via a rheostat on the headband Bright illumination that adjusts to 2% of maximum Wide-angle diffuser to eliminate shadows on the edge of the condensing lens that significantly expands the field of view PD range: 48mm-76mm Requires optional power supply