| Glass lenses are available in 1.523, 1.6, 1.7, 1.8, and 1.9 refractive index – the higher the index the thinner the lens - however glass lenses are roughly twice the weight of plastic lenses so they are less comfortable. Additionally glass can shatter and cause serious eye injury if you are at risk of breaking the lenses (for example doing DIY or playing sports). Except for the very thinnest 1.8 and 1.9 lenses where there is no plastic equivalent for very short sighted people glass is rarely dispensed these days. |  |