A Report on Experiments with Toyo ‘s Super‐Gus‐Permeable Hard Contact Lens: Paper presented at the International Contact Lens Congress, Fiji, July 1978.

Abstract

Among the recent developments in the field of hard contact lenses, attention has been focused on a new type of lenses with high oxygen permeability. In 1977 the staff of the research division of the Toyo Contact Lens Co. Ltd succeeded in developing a new polymer with extremely high oxygen permeability based on an entirely new monomer made of esterifies methacrylic acid. They have named this new material ‘PHCL’, denoting a gas permeable hard contact lens. The PHCL has the following two primary features. The first feature lies in its excellent gas permeability. The permeability of the PHCL is measured to be 1.4×10--10ml. cmlcm2.sec.mmHg., which is about 2.5 times the permeability of other gas permeable hard contact lenses and about twice that of 2–Hema polymers. The second feature is the good wettability of the new material. The wettability is usually estimated by the contact angle. The contact angle of the PHCL is measured to be 23°, showing a remarkable improvement from the contact angle of PMMA which is about 63“. These two features will definitely contribute to the physiological integrity of the cornea and the comfort in wearing contact lenses. Our report includes the comparison of the PHCL with other gas permeable hard contact lenses and several soft contact lenses with respect to the following points: 1) reduction of glycogen granules in rabbits' eyes; 2) histological studies by HE staining; 3) corneal thickness changes measured by pachornetry with human eyes. The data indicates superior quality of the PHCL to other materials in terms of maintaining the normal metabolism and physiology of the cornea.