| abstract |
Soft contact lenses are manufactured from polyvinyl alcohol (PVA) having tensile strength of 10 kg/cm2 or more; moisture content 40-90% by wt.; visible light transmittance 90% or more; and oxygen permeability at least 3 x 10 power-10 cm3.(STP.cm/cm2. sec.mmHg. The PVA pref. has pore dia. below 3 micron. The lenses are prepared by dissolving the PVA in a mixt. of water and an organic solvent (90:10 to 10:90 by wt.) to give a soln. contg. 2-30% by wt. of PVA. This soln. is poured into a mould of suitable shape and crystallised at below room temp. The crystallised PVA may then be cross-linke d either by irradiation with electrons or emission radiation or chemically (e.g. with glutaraldehyde). The organic solvent is a water-miscible one such as dimethyl sulphoxide, glycerol, ethylene glycol, propylene glycol, triethylene glycol, dimethylformamide, methanol, ethanol, acetone, tetrahydrofuran, aminoethanol, phenol, propanol or isopropanol. |