Spherical Corrective Lenses
- 223 Downloads
Glass has been most frequently used for spectacles. Quartz and rock crystal had a certain success in the 19th century (homogeneity, hardness, low dispersion, high conductibility of heat, which reduces fog). However, it is costly and transparent to harmful ultraviolet rays. For glass, we generally use a crown glass of index 1.51 < n < 1.53. Flint glass, or crown glass with a high index, would decrease curvature, but this advantage is of little consequence. Transparent plastic materials avoid breakage and are lighter than glass. Their use is becoming more frequent. Contact lenses are always made of plastic.
KeywordsShape Factor Intraocular Lens Crystalline Lens Corrective Lens Rock Crystal
Unable to display preview. Download preview PDF.