Toric Contact Lenses

Nowadays there are many types of contact lenses on the market. Most of them are being fitted in order to help the vision, such as correcting basic near and long sightedness. However, because many people are in need of a correction for astigmatism, the lens manufacturers are now producing soft contact lenses which cater for this large segment of contact lens wearers. (The term astigmatism stands an eye condition that normally happen when the front surface of the eye, the cornea, has an irregular curvature and as a result the eye can't focus a point object into a sharp focused image on the retina).

Originally the development of “toric” contact lens (lenses which are correcting astigmatism) was very slow to due to the fact that rigid or hard contact lenses usually compensates for astigmatism because of the layer of tear film between the contact lens and the irregular shaped astigmatic cornea. With the introduction of the soft contact lenses the issue of compensating astigmatism became more prominent and in order to further improve market share the manufacturers of soft contact lenses started to invest a lot of capital in the development of toric lenses.

The main issue was not how to produce a toric power in the contact lens but how to stabilize the contact lens on the eye so it would not rotate or swivel. Astigmatism should be right under a certain axis, any “off axis” placement of the lenses will result not clear vision. The compensation of  astigmatism meant that the contact lens was not allow to rotate more than a few degrees after blinking and then it should return quickly to the original position. A lot of experimenting went on and with this the development of “corneal mapping’ equipment was developed.

The first mainstream toric soft lenses were tailor-made lenses and as a result the cost of this type of lens was very high. Most of them needed replacement after 12 months and to replicate them accurately was not always successful. The contact lens wearers often complained about the difference in comfort or vision in case when the previous pair was produced more accurately to the manufacturers’ standards. In a lot of cases it was a matter of the human element (technician’s skills) rater than quality of manufacturers tooling. After a few years with the introduction of computer guided lathes and polishing machinery the consistency in quality improved and as the manufacturing cost per contact lens went down the availability and affordability made the toric soft contact lens a mainstream lens.