High Index Lenses
Basic lenses come as a standard thickness (index) and are more commonly made of plastic.
The stronger your prescription the thicker your lenses are likely to be, which not only might make them uncomfortable to wear, but also limits your frame choice and impacts overall appearance which can leave the customer disappointed.
Lenses with a “High index” help reduce the thickness and can create a more aesthetically pleasing overall result. The higher the index of the lens the thinner they will be once finished.
High index lenses are available in plastic, glass, Polycarbonate and Trivex.
Plastic lenses (CR39) are reasonably tough and are available in increasing high indexes.
Indexes available are 1.5 (standard), 1.6, 1.67 or 1.74
Polycarbonate lenses are extremely light but are susceptible to scratching and chemical attack from solvents. These only come in one index option of 1.59.
Glass lenses can give the thinnest finish of all the lens makes and are highly scratch resistant, however care needs to be taken as they can break if dropped.
Indexes available are: 1.523, 1.6, 1.7, 1.8 or 1.9
Trivex are very tough and are good in safety glasses. These only come in one index option of 1.53.