Eyeglass Lens Materials
Glass lenses are still available but because they are heavier than plastic lenses and
can shatter they are rarely used today. However some individuals still like them and
they are available in clear, photochromic, poloroid and gray and brown tinted
lenses. In some cases High Index glass lenses are available.
Plastic lenses come in many different materials and index of refraction. The higher the index of refraction the thinner and lighter the lens.
Standard plastic lenses ( index 1.49) are inexpensive and have excellent optics. They are suitable for low prescriptions. They should not be used in rimless frames or in high prescriptions.
Polycarbonate lenses (index 1.58) are thinner, lighter in weight and still economical lenses. They are stronger than plastic bit not the strongest lens material. While they are good lenses, in higher prescriptions they can have more chromatic aberrations than most other lens materials. Polycarbonate lenses are suitable for grooved rimless frames and can be used in drilled rimless frames but in drilled rimless frames they can crack and are not the best material.
Mid Index Lenses include Trivex 1.54 index, 1.56 High Index, and 1.60 Hi Index.
Trivex is a mid index lens that is excellent for use in all kinds of frames and is a preferred material for drilled rimless frames. It has excellent optics as do all of the lenses in the mid index category. Trivex, 1.56 Mid Index, and 1.60 mid index are excellent lenses for moderate prescriptions.
1.67 Hi index lenses are the premium and preferred lens for many prescriptions offering strength and thinness combined with excellent optics. They are suitable for use in all rimless frames. They are
thinner than polycarbonate lenses.
1.74 Ultra Hi Index is the thinnest plastic lens material and is recommended for very high prescriptions.
Aspheric Optics and Digital Optics
All of the above lenses can be made with aspheric or with digital optics.
Aspheric lenses are flatter, thinner and have less bulge in plus prescriptions and have more clarity in a lens edge to edge.
Digital lenses are lenses made in a new way that are the wave of the future in making lenses with clearer edge to edge optics.