The Keeler Standard Ophthalmoscope is designed with a positive maywheel lens control that allows you to click through lens powers from +40D to -25D allowing detailed examination of the ocular structures and ease of use for spectacle wearers. This Standard ophthalmoscope has two diagnostic beams, a wide angle beam for general examination and a macular beam for more detailed examination of the central retina. A red free filter for enhanced vessel examination can be used with both diagnostic beams, particularly useful for diabetic assessment and monitoring. The integral soft brow rest allows for easy positioning and protects your lenses if you are a spectacle wearer. The Standard ophthalmoscope has a slim line handle for easy grip and is powered with a 3.6v dry cell battery.