High strength ophthalmic lens

Claim 1

A chemically-strengthened ophthalmic glass lens made from a phospho-silicate glass having the following chemical analysis: ______________________________________ Ingredient Percent by Weight ______________________________________ sodium oxide about 4 to about 15 potassium oxide about 3 to about 15 Other Alkali Metal Oxides: lithium oxide up to about 5 rubidium oxide up to about 5 cesium oxide up to about 5 lanthanum oxide up to about 15 aluminum oxide up to about 5 zirconium oxide up to about 5 zinc oxide up to about 15 calcium oxide up to about 10 titanium oxide up to about 5 magnesium oxide up to about 4 boron oxide up to about 2 phosphorus pentoxide about 3 to about 15 Total Na.sub.2 O + K.sub.2 O and other alkali metal oxides about 12 to about 20 Total ZnO + La.sub.2 O.sub.3 + CaO + MgO about 8 to about 15 Total MgO + Al.sub.2 O.sub.3 about 0.2 to about 5 Fining Agents (antimony oxide, cerium oxide, arsenic oxide and mixtures thereof) up to about 2 silica balance ______________________________________ said lens characterized by an index of refraction in the range of about 1.50 to 1.52 having a minimum depth of penetration of potassium ions of 120 microns and a compressively-stressed surface layer having a strength of at least 25,000 psi.