Lens materials an explanation
Lens materials and explanations:
Your optometrist at EyeZone will recommend a variety of lenses to suit your particular needs, here we want to remove the scientific veil and bring you behind the curtain, or to be exact behind the ophthalmoscope. After your eye test is finished, if it is found you need glasses, your optician will recommend a variety of products; the optometrist will of course know what exactly is best to suit your needs. But we wanted to help you decipher the recommendations, below is a brief description of what the different types of materials and lens types are. From this you may find out what will suit your particular needs or at least remove any confusion.
The first thing to say before we start is that eye glasses are not made of glass, anymore, it has been many years since we covered our eyes with glass lenses, but to this day the name persists. Lenses now are made of plastic; the reason for this is twofold.
Firstly for safety, imagine if you where to fall and break your glasses, not only would you have to worry about the fall but the hazard of shards of glass going everywhere.
Secondly cost, glass is cheap to make when it is a simple flat surface, but the costs to make the curve specific to your eye would drive the costs of your glasses very high. Add to this the costs of coating your particular glasses with an anti reflective or anti scratch requirement necessarily to your individual prescriptions and soon your bill would be unpalatable. To this end eye glass lenses are made of different types of plastics, these have the benefit of being easily and quickly replaceable as well as adding an element of safety which is demonstrated below.
These are our normal plastic lens and are the world’s most widely used lens material. They are suitable for a range of prescriptions and are generally more suitable for lighter prescriptions. This is the minimum standard in lenses and has been the standard for a long time. The lenses will be cut and shaped to suit your needs and range in prescriptive strength. CR39 plastic lenses are the easiest lenses to tint and add coating too, but on the other hand they tend to be bulkier lenses as you move up the indexes but they are usually the most cost efficient lenses.
Mid & High index Lenses, 1.56, 1.6 1.67 & 1.7
These are a great option for those wanting that thinned down material in lenses, while retaining the strength of the thicker lenses. With rimless and wire frame materials more common in modern glasses it is a great option to put a thinner lens into those designer frames to complete the package. The higher the index goes, the higher the cost, this is related to the level of thinning that is required in higher indexed lenses.
These are tougher lenses and come with UV blocking built in. These are meant for a more active lifestyle and are great for children’s eye wear, because as we all know if it can be broken, children will break it. This material is the type of material used in bulletproof vests and the lenses are so tough that they have become the standard in safety eyewear and are the standard material used in EyeZone safety glasses.
Trivex is a newcomer to the lens family and like polycarbonate it also has built in UV blocking system. The material claims to be stronger than polycarbonate and has less internal stress so there is less rain bowing of light. Both materials feature shatter resistance but because of the less internal stress Trivex will not fracture in the same was polycarbonate does. Both materials are strong enough to meet the needs of any active life, and tests by various manufactuirers have shown that both can stop a bullet, although this is not a common issue any of us has.
The above gives you an overview of what materials are available for your lenses, if you have any further questions you can ask you local optometrists and they will help you in your selection process.