Prism form: Base up,base down,base in,base out Specifications Sphere: 0.0 to -29.50 Diopters, step: 0.25,0.50,1,3 0.00 to +26.75 Diopters,step: 0.25,0.50,1,3 Cylinder: 0.0 to ± 8.75 Diopters,step:0.25 Prism form: Base up,base down,base in,base out Binocular balance: Rotary prism,polarizing filter and R & G filter Cross cylinder: ±0.25D ,±0.37D ,±0.50D PD: 48 to 80mm in 0.5mm step Retinoscope: +2. ...