Ergonomically designed for maximum comfort, balance, and access to controls. Aperture dial allows you to select micro, small, and large spot sizes. Also includes red-free filter and slit aperture. Dynamic Focusing Wheel adjusts the focus in a continuous, smooth action for more precise control and optimum view. Available focusing range is from -20 to +20 diopters. Patented Glare Extinguishment System prevents interference from unwanted glare and reflections. Patented Axial PointSource Optics makes it easy to enter undilated pupils, and provides a 25° field of view, resulting in a view of the fundus that's five times larger than you see with a standard ophthalmoscope in an undilated eye. Halogen HPX™ lamp provides whiter, brighter light. Cleanable, reusable eyecup establishes and maintains proper viewing distance, provides image stability, serves as a pivoting point for panning around the retina, helps with orientation, and screens out ambient light. Compatible with any standard 3-1/2-V power source including desk charger handles, convertible battery handles, wall transformers, and the lithium ion power handle.