The Welch Allyn 11710 Ophthalmoscope has 28 lenses from -25D to +40D. This standard instrument features halogen illumination for ture tissue color and longlife. Rubber brow rest prevents scratching of eyeglasses. Illuminated lens dial clearly identifies setting in darkened exam room. The Welch Allyn 11710 Standard Ophthalmoscope is a basic model with three spot sizes, target, slit, and red free filter.