Another lens parameter is the center thickness (c.t.) of the lens. The center thickness varies depending on the other lens dimensions. The most important controlling factor is the lens power. Minus lenses have thinner centers than plus lenses.
The minimum center thickness
commonly used with RGP lenses
is 0.10 mm and with many materials
it is not less than 0.14 mm.
With hydrogel lenses it is common for minus lenses to have center thicknesses in the range of 0.035 mm to 0.10 mm.
