There is disclosed an improved optical device of the type disclosed in application Ser. No. 520,456 and embodying an array of lenses integral with and raised above a crystalline matrix. The improvement comprises an ion-exchanged surface on the lenses wherein the lithium ion from the lens glass is exchanged with a larger monovalent ion, preferably sodium or potassium from a bath, and the contents of such alkali metal ions in the lens are defined by both radial and axial concentration gradients. The device may be heated above the glass strain point to relieve stress and enhance lens power, either simultaneously with or subsequent to the ion exchange.