ZEISS OPHTHALMOMETER

Making the measurement:

If the cornea is toric, the two crosses will not 
appear to be on the same axis.  In this case the 
body of the instrument must be rotated until 
they appear on the same axis.  The power is 
then measured as before with the central screw 
in the handle.  The axis is read in the left 
window (1) in the instrument.  The body of the 
instrument must then be rotated 90 degrees to 
measure the second principal meridian.