Before revision: Lens materials Optical crown glass (B270 - Soda/lime glass) Refractive index ( nd ): 1.52288 Abbe value (Vd ): 58.5 Density: 2.56 g/ cm3 (the heaviest corrective lens material in common use, today) UV cutoff: 320 nm Glass lenses have become less common owing to the danger of shattering and their relatively high weight compared to CR-39 plastic lenses.
After revision: Lens materials Optical crown glass (B270 - Soda/lime glass) Refractive index ( nd ): 1.52288 Abbe number ( ): 58.5 Density: 2.56 g/ cm (the heaviest corrective lens material in common use, today) UV cutoff: 320 nm Glass lenses have become less common owing to the danger of shattering a their relatively high weight compared to CR-39 plastic lenses.