SAN MARCOS, Calif.—Signet Armorlite announced the results of a study that found that a new type of “anti-fatigue” lens featuring a base-in prism design can alleviate symptomatic convergence insufficiency (CI) in presbyopes.

The double-blind study, a combined effort between the Illinois College of Optometry and Signet Armorlite’s Crossbows facility in Northern Ireland, was conducted during 2008 to document the effects of base-in prism to relieve CI symptoms in a test group of presbyopes. According to Signet Armorlite, the test results proved the concept, and the Crossbows engineering staff developed a patented “Anti-Fatigue Progressive Technology.” The technology is being applied to Signet Armorlite’s Kodak line of progressive lenses, produced at its Signetek lab here.

The concept of incorporating base-in prism in a progressive design to relieve convergence insufficiency symptoms was conceived and patented by Jeffrey Krall, OD of Mitchell, S.D.

“While a patient’s eyes will naturally drift outward when performing lengthy near work, the process of turning the eyes in to maintain fixation can lead to such symptoms as eyestrain and visual fatigue that may result in headaches,” said Krall. “But the base-in prism in the reading area can assist the normal binocular function of a patient’s eyes for more comfortable near work for longer periods of time.”