Welch Allyn 3.5V Standard Ophthalmoscope (Head Only) Our Standard Ophthalmoscopes feature halogen light for true tissue color and consistent, long-lasting illumination, and six apertures for general and specialist use. Halogen light for true tissue color and consistent, long-lasting illumination. 6 apertures for generalist use: micro, small, and large spot sizes, fixation target, slit aperture, and red-free filter. 28 focusing lenses with a range of -25 to +40 diopters. Rubber brow rest prevents scratching of eyeglasses. 3.5V Halogen Ophthalmoscope, Head Only High-intensity halogen illumination and mirror optical system 28 lenses with illuminated lens dial Apertures (microspot, small spot, large spot, fixation, red-free, and slit) for all diagnostic applications