H4 contact lenses are spherical lenses from Bausch and Lomb designed to correct the vision of patients suffering from hyperopia and aphakia.  H4 lenses are manufactured using "spin-cast" technology and are designed as daily wear lenses to be replaced after up to one year of use.

Lens Material
The lens material (polymacon), is a hydrophilic polymer of 2-hydroxyethyl methacrylate, and is 38.6% water by weight when immersed in saline solution. These lenses are hemispherical flexible shells.

Lens Parameters
Chord Diameter:	14.5mm
Center Thickness:	0.42mm to 0.60mm
Base Curves:	Median
Powers:	+6.50D to +20.00D (in 0.50D steps)

Lens Properties
Specific Gravity:	1.12
Refractive Index:	1.43
Surface Character:	Hydrophilic
Water Content:	38.6%
Oxygen Permeability (Dk):	8.4
Oxygen Transmission (Dk/t):	1.6