Specifications Ranges of diopter measurement 0 - ±25D Minimum scale value 0.125D at 0 - ±5D 0.25D at ±5D - ±25D Astigmatism axis of cylinder lens 0-180? Minimum scale value 5? Prism diopter at 1å ìÂÂÂÂìÂÂÂÂinterval in the range of 0 - 5å ìÂÂÂÂì at 1å ìÂÂÂÂìÂÂÂÂinterval in the range of 0 - 20å ìÂÂÂÂì Prism base angle 0-180? Minimum scale value 5? Regulation of ocular visibility ±5D Size of lens Ø16mm - Ø80mm Overall dimensions of device 275mm?30mm?55mm Weight 5.6kg Lighting lamp 220V15W 110V15W