Period Costs. Period costs are expenses that are easier to attribute to times and accounting periods than actual production processes or finished goods. Typically, managerial accountant want to classify expenses in categories that can improve operations. Manufactures tend to focus on functional classifications.
The amber color of these impact-resistant polycarbonate lenses block short-wavelength blue light and 100% of ultraviolet (UV) light, thus providing additional protection against cataract formation and the development of macular degeneration, while increasing contrast on both sunny and bright hazy days.
Polycarbonate, however, is not without its drawbacks. One of the chief complaints about polycarbonate is its optical quality, or lack thereof. With an Abbe value of 29, polycarbonate's chromatic aberration is the highest of any lens material in use today. Furthermore, with the increase in popularity of drill mount frames, some dispensers are hesitant to use polycarbonate because of its lack of tensile strength and likelihood of cracking around drill holes.