Fig. 6. Spectral transmission curves for different lenses. A. Prescription lenses, clear glass; prescription lenses, clear plastic; gray hard contact lens. B. UVR-blocking sunglasses, inexpensive ($10 price range) and expensive ($150 price range). C. Photochromic lens, unexposed (faded) and exposed (darkened) at 25°C. (Javitt JC, Taylor HR: Focal Points: Clinical Modules for Ophthalmologists 9(3). Reprinted with permission from the American Academy of Ophthalmology, 1991)