Prism by Decentration

Normally, eyeglasses are fitted with the optical center of the lens directly in front of the eye. If the lens is fit off-center, image displacement can occur due to induced prism. The higher the power or the further the lens is fit off-center, the higher is the...

Trivex vs. Polycarbonate

Poly and Trivex: Facts and Fiction Even though Trivex has been available for years and polycarbonate for decades, there is still much debate, confusion and even long-held myths about how Trivex and polycarbonate stack up against one another. We'll lay out the facts,...

Understanding Prism Thinning

The curvature of a progressive addition lens surface gradually increases toward the bottom of the lens, becoming increasingly steeper. This increase in curvature (and surface power) is what produces the add power of the progressive lens. Unfortunately, because the...

Methods for Estimating Lens Thickness

Often, it is beneficial for the eye care professional to predict the finished thickness of a pair of spectacle lenses. Determining the change in thickness that results from the patient's use of a different frame or lens style is a common example.Patients investing a...

Basic Refraction Procedures for Opticians

Many opticians around the country have shown great interest in learning the procedures involved but have been unable to take a course on the subject. This article is designed to introduce the subject to those interested, and to provide some continuing education to...

The Electromagnetic Spectrum

Produced by the nuclear cauldrons of stars and all matter in the cosmos, energy in the form of electromagnetic radiation permeates our entire universe. Every second of every day we are bombarded with and surrounded by electromagnetic radiation; some bounces off of our...