LENS DESIGN


BACK OPTIC ZONE

When viewed through the lens (from 
the front or back of the lens) the 
section formed by the base curve is 
called the optical zone or back 
central optic.  The diameter of this 
portion of the lens is called the 
optical zone diameter (OZD); 
posterior optic zone diameter (POZD); 
or back central optic diameter (BCOD).  
It is the linear distance from one edge 
of this zone to the other edge.  Optic zone diameters for rigid lenses are typically 7.5 to 8.5 mm.  This is the portion of the lens that the patient looks through and has the patient's correction.