Snap-On vision charts are easily changeable to accommodate different language symbols. The standards are Numbers, Letters, Landolt C, and Tumbling E. Call and ask for pricing of custom charts. For ETDRS charts the substrate is opaque, which reduces illumination to 85 cd/m2 for reading. For potential Vision charts, the substrate is translucent, which allows chart illumination up to 6000 cd/m2.