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 bottom of the lens is steeper than the top of the lens, the upper edge of a progressive lens blank is thicker than the lower edge. Understanding Prism Thinning (pdf) by Darryl...

Read More

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 considerable amount of money into thinner and lighter lenses want to know just how thin their new lenses will be. This is a question that often strikes fear in the hearts of unprepared opticians. Those armed with the knowledge required to provide the answer, however, quickly earn the respect of their patients. Even these opticians...

Read More