Center thickness

Related to the term – contact lens transmissibility (Dk/t)

The Dk value determines the properties of a contact lens material. A contactologist has to take the thickness of the lens (in cm) into consideration as well as the permeability. Together they form the Dk/t value, called transmissibility, which characterises a lens.

The unit is defined in Barrer/cm. This value is usually listed by manufacturers only for contact lenses with –3.00 D and the t value is defined as the center thickness, that is, the thinnest part of the lens, which can be slightly misleading for contactologists.