Optician India

Welcome to question of the day #99

I advised one of my patients to have an anti-reflective coating on her -0.75 DS spectacle lenses. She queried the benefits. How should I reply?

There are three benefits from coating lenses, even low powered ones, with anti-reflection coatings.

Firstly, they increase the amount of light that enters the eye. Depending on the refractive index of the lens material around 4-10% of incident light is reflected at the front surface of an uncoated lens. Some will be reflected internally as light leaves the rear surface of the lens but an anti-reflection coating cannot influence this. So, with an uncoated lens, the eye only receives 90-96% of the incident light and with an anti-reflection coating, it is around 100%. Eyes work better with light.

Secondly, an anti-reflection coating on the rear surface of a lens (surface closest to the eye) will prevent light that is reflected from the eye and skin around the eye as well as light incident from direct sources from being reflected into the eye. This type of light re-reflected into the eye causes glare and haloes around lights and all the negative visual consequences associated with those phenomena.

Thirdly, anti-reflection coatings make the lenses look almost invisible to people looking at the person who is wearing them. The higher the refractive index of the lenses the more benefit anti-reflection coatings provide in terms of how the lenses look.

The new generation of anti-reflection coatings are tough, durable and provide superior vision. The word "coating" is really a misnomer. The coating is fused or ‘baked’ onto the lens matrix. Newer generation coatings also contain chemicals that make them hydrophobic, which means that the lens surface will reduce the adhesion of water and grease. This keeps the lenses cleaner for a longer period and makes them much easier to clean when they do become dirty.

Help your patients have 100% of the vision available to them by recommending anti-reflection coatings on their spectacle lenses.