Prism Spectacles (also known as PrismSpecs in the SNES/PS version) are an accessory in Chrono Trigger.
It is often considered one of the best accessories to have (outside of certain situations such as dealing with fixed damage, relying on critical hits or focusing on MP consumption) since it boosts not only physical damage but magical as well. Clear both the Sun Stonesidequest and The Rainbow Shell sidequest and Melchior will combine the two items to produce the Prism Spectacles and Rainbow. Along with Prism Helm and Prism Dress, these psychedelic lenses are one of three non-offensive items created from the Rainbow Shell. Steel Shade can be charmed by Ayla for this item.
Stacking with other damage boosting items
Prism spectacles stack multiplicatively with the Master's Crown (only available in the DS version, and only allowed to be worn by male characters), yielding an effective 1.875x damage modifier.
Prism spectacles do not stack with Sunglasses, as only one accessory can be worn at a time.