Heine BETA 200 Ophthalmoscope Head The ultimate in performance and quality, BETA 200 Ophthalmoscopes utilize Heine's patented Aspherical Optical System (AOS), avoiding corneal and iris reflections to provide crisp, clear retinal images even in the case of small pupils. The biggest challenge in achieving crisp, clear images of the retina with a direct ophthalmoscope is corneal and iris reflex, which can obscure the observer's view. Unlike polarizing filter-based solutions, which reduce illumination and image quality, the Aspherical Optical System (AOS) avoids corneal and iris reflex and maximizes image contrast, clarity, and resolution. Based on the Gullstrand Principal, the AOS produces a flat illumination beam, and then effectively separates the path of the illumination from the path of observation. As the flat beam of light enters the lower half of the cornea, the curvature of the cornea diverts all reflexes down and away from the observation path. Once past the anterior chamber, the light beam opens up dramatically to illuminate a large area of the retina. The observer now looks through a clear area of the cornea without annoying reflexes, and is able to view the whole illuminated area of the retina. The result - crisp, clear, and complete retinal images.