From the above link:
The most noticeable difference deals with eye protector impact levels. Two levels of impact resistance, “Basic” and “High” are now defined for safety glasses. Marking requirements changed to reflect these levels of impact performance. Devices that meet the “High” impact criteria must be marked “Z87+”. Frames should meet the “High” impact level. If the eye protector only meets the “Basic” impact criteria, a warning label must be attached to the protector.