This is a very basic and simple approach to explaining aspheric lenses. They feature a different lens design than the standard spherical lens. To understand the aspheric concept, you have to consider two components of a lens that affect how light travels through the lens. The first is the index of refraction and secondly is…

Vitamin A – We all remember our mothers telling us to eat our carrots so we could have eyes like an eagle. Why did our mothers tell us this? What do carrots really do for us? Carrots contain a carotenoid called beta-carotene. Carotenoids are pigments in plants and animals that provide red and yellow color….

The Development of Opticianry In early times customers made their selection from a tray of eyeglasses which were already assembled and which contained standardized non-prescription lenses. Today, this same procedure is still followed in some novelty and drug stores where ready made reading glasses are selected from a display. As could be expected the practitioners…

Different lenses have different properties. The density varies, known as index of refraction, and the ABBE VALUES are different for the various materials. The ABBE VALUE is a number given to describe the amount of chromatic aberration of an ophthalmic lens material. Here is a list of ABBE VALUES. The higher the number, the less…

FACT – UVA & UVB RAYS ARE HARMFUL More and more people are aware of the dangers caused by the sun. Your eyes, as well as your skin are at risk every time you step outside. You can reduce the risks of damaging your eyes by wearing sunglasses. What does ultraviolet (UV) mean? Ultraviolet is…

All about anti–reflective coatings Anti-reflection coatings are made from extremely thin layers of different dielectric materials that are applied in a high vacuum onto both surfaces of the lens. The quality of the AR depends upon the number of layers applied to the lens. The early coatings had only a single layer of magnesium fluoride…

SLAB-OFF EXPLAINED On occasion we have patients who come in with a prescription showing a significant power difference between the right and left eyes. Sometimes this variance is rather significant, around four diopters, or less significant, at around two diopters. This condition is called anisometropia, and is often congenital but can also be caused by…

The Issue of Adaptation “These aren’t working for me.” This isn’t what we want to hear from our patients. Before you fit progressives, please consider the following variables and realize that adaptation issues are a challenge that every Optician faces. If working with a multifocal patient, is this their first multifocal, or are they transitioning…

Tints, Filters and Sunglasses Tinted lenses are worn for the sake of appearance, comfort (discomfort glare), vision (disability glare) and protection against UV exposure. Sunglasses typically reduce transmission to 15%-25% and can be even darker for very bright conditions such as snow. At least 8% transmission is required to drive a car safely. Wearing sunglasses…

By definition an ophthalmic prism is wedge-shaped lens of glass or plastic that is thicker at one edge (the base) than at its opposite edge (the apex). Prisms usually are prescribed to correct faulty eye-muscle imbalances in which both eyes do not act as a team. In these cases, the refractive doctor prescribes the proper…