(a) providing a photosensitive aza-crown ether or crown ether of a chromene or a diazene compound that releases lithium upon exposure to light;

(b) administering an effective amount of the aza-crown or crown ether of a chromene or a diazene compound in a pharmaceutically acceptable carrier to the eye of the subject; and

(c) exposing the eye of the subject to an external light source to cause the aza-crown ether or crown ether of a chromene or a diazene compound to release lithium wherein the photosensitive aza-crown ether or crown ether moiety of a chromene or diazene compound has one of the following structures:

wherein Q is a crown ether or an aza-crown ether;

wherein R1, R2, R3, R′1, R′2, and R′3, are the same or different, and are each a phenyl ring or a substituted phenyl ring, a hydrogen; a halogen, a hydroxyl group, an unsubstituted or substituted lower alkyl, cycloalkyl, aryl, acyl, alkoxy, acylamino, aralkyl, cyanocarboxyl, thio, vinyl, stryryl, alkoxycarbonyl, carbamoyl, aminocarbonyl, or phenoxycarbonyl; and wherein X1 and X2 are each a phenyl ring or a substituted phenyl ring, an unsubstituted or substituted lower alkyl, cycloalkyl, aryl, acyl, alkoxyl, aclyamino, aralkyl, cyanocarboxyl, thio, vinyl, stryryl, alkoxycarbonyl, carbamoyl, aminocarbonyl, or phenoxycarbonyl.