Lens coatings

 

These days most ophthalmic lenses are coated. This means that the base lens material has a varnish type finish applied to it in order to enhance the scratch resistance of the surface. This varnish only coating is generally referred to in the industry as a hard coat.

Another type of coating that is often applied over the top of the hard coating is the anti reflective coating. Antireflective coatings have two basic advantages. Firstly they have a cosmetic value due to the reflections on the front surface of the lens being diminished so that the wearer’s eyes can be more visibly seen. Secondly they assist the wearer’s vision by reducing the reflections on the back surface of the lens thus enhancing the wearer’s vision. Below is an image showing the difference in front surface reflections between a standard coating and an antireflective coating.

As you can see the lenses in the left hand image are very reflective. The lenses on the right have an antireflection coating which absorbs the reflected light giving a much better appearance.