What unit of measurement is used with the Chord Diameter?

Chord diameter is an essential measurement in the field of contact lenses, specifically refers to the diameter of the lens when viewed from the front. It is the distance across the lens at its widest point, measured in a straight line. The correct unit of measurement for chord diameter is millimeter. This is due to the small sizes involved in contact lenses; millimeters provide a more precise measurement than centimeters, meters, or nanometers, which are either too large or too small for effective use in this context.

When fitting contact lenses or designing them, it is crucial to have accurate measurements, and using millimeters allows for the necessary precision to ensure a proper fit on the cornea. Understanding the significance of chord diameter in relation to contact lens fitting can enhance the overall success of lens wear for patients.