“Eye miniatures or Lovers' eyes were Georgian miniatures, normally watercolour on ivory, depicting the eye or eyes of a spouse, loved one or child. These were usually commissioned for sentimental reasons and were often worn as bracelets, brooches, pendants or rings with richly decorated frames, serving the same emotional need as lockets hiding portraits or locks of hair. This fad started in the late 1700s.”
The lovers eye could signify celebration, mourning, happiness or sorrow. This one I have replicated is an exact match to one from the 1700s.