Contac lenses

Contact lenses

Contact lenses improve our vision and they correct the eyesight of 90% of people suffering from a refractive error. For some conditions, such as strong myopia or strong cornea curvature, contact lenses are even more efficient than glasses.

Contact lenses have been very successful thanks to the manufacture of materials that can be permeated by oxygen and tolerated by eyes. In 1509, Leonardo da Vinci had already tried to correct vision conditions with optical systems which implied direct ocular contact. Contact lenses as we know them today, made in plastic and adaptable to the cornea’s shape, are used since the thirties.

Nowadays, 20% of the population of the US with refractive error problems use contact lenses while in Western Europe it is only between 7 and 9% of the population. However, this percentage is on the rise thanks to the development of new and more comfortable materials.

Types of contact lenses

Hard contact lenses were the first type to appear, followed by RGP contact lenses. The last type to be developed has been the soft contact lenses, with a higher percentage of water content.

 

Originally, contact lenses were exclusively made of polymethyl methacrylate (PMMA). Hard contact lenses present excellent optical properties and they are very easy to clean and maintain. However, PMMA is not oxygen-permeable, and they are not easily tolerated by eyes.

Contact lenses made of silicone and fluor are more oxygen-permeable.

Thus, RGP contact lenses were developed.

Soft contact lenses have been manufactured since the sixties. They are mainly made from hydroxyethyl methacrylate and their water percentage ranges from 50 to 85%. The higher the water proportion, the higher the oxygen-permeability.

Water proportion can be increased by including other compounds to HEMA. New biocompatible materials and silicone lenses have become an alternative solution for those who are intolerant to other types of contact lenses.

Nowadays, soft contact lenses can be classified in two different groups: conventional and disposable.

Conventional contact lenses need to be replaced every year or every year and a half. It is essential to follow the maintenance routine accurately.

Disposable contact lenses need to be replaced frequently. Every manufacturer will determine for how long every type of lens can be used, going from 1 to 30 days.

 

Advice about contact lenses:

It is important that contact lenses are adapted by a professional.

The type of lens will depend on different factors such as the cornea curvature, the type and quantity of tears, the use, etc.

Daily hygiene is very important to avoid infections or ocular alterations. In case of any discomfort, you should visit an optician to avoid developing an incompatibility to the material.

It is important to follow replacement instructions. If the replacement limit is surpassed, manufacturers do not guarantee the lens material properties.