GJD-7 Portable Focimeter Lensmeter Optical Instrument 1.Internal reading Lensmeter 2.±25D measurement 3.Wide field of vision observation Ranges of Measurement 0 to ±25D Minimum Outer Reading:0.125D Inner Reading:0.125D graduation up 0 to ±5D and 0.25D graduations over±5D to ±25D Cylinder Axis Range 0-180°step 1° Primatic Power Range 0-5prism diopters,graduations with prism compensation device 0~20prism diopters, 1graduations Prism Base Angle 0~180° Eyepiece Adjustment ±5D Dimension of Objective Lens Φ16~Φ86mm Overall size 275×120×430mm Weight 4kg Lighting Bulb ~220V/-3V 3W or ~110V/-3V 3W