How to use and adjust loupes
Structure of loupes
This adjustment is controlled by turning the interpupillary adjustment knob back and forth,
until the image converges into a circle.
For Kepler Loupes(4.0x to 6.0x), each optics can be independently adjusted until the image
coverages into a circle.
Adjust the hinge mechanism
Follow the drawing to adjust the hinge mechanism, so that the optics are angled approximately 30 to
45 degrees below a horizontal line. This will allow  the user to look down into the optics while working,
while still allowing you to maintain an upright, ergonomic posture.
Fit on the sideshields from the tail of the frame, The sideshields will prevent aerosl spray of
water, blood, and saliva from entering the eyes
There are two mounting hole on the hinge. If the loupe lens is short, fix lens onto the back hole. If the  
lens is long, fix the lens onto the front hole to prevent the ocular from touching the glass.