... Phoropter,view testerSpecifications Sphere: 0.0 to -29.50 Diopters, step: 0.12,0.25,0.50,1,3 0.00 ... °,5°,15° Prism: -20 to +20, step:0.1,0.5,20Prism form: Base up,base down,base in,base out Near distance ... 50D PD: 48 to 80mm in 1 and 0.5mm step Retinoscope: +2.00D or+1.50 both sides Corneal alignment ... : 12 to 20mm by 2mm step and 13.75mm Field of view: 35° Power source: ...