... .5V, 1.6W;19 lenses from 0D to 20D. The direct ophthalmoscope is used for examining the interior structures of the ... , ±3D, ±4D, ±6D, ±8D, ±10D, ±15D, ±20D.5. Aperture wheel: red-free filter, Large spot, small spot, hemispot.Technical Specification:Name ... : 0D, ±1D, ±2D, ±3D, ±4D, ±6D, ±8D, ±10D, ±15D, ±20DAperture: red-free filter, Large spot, small spot, hemispotRated voltage: AA alkaline ...