Abstract

Laser patterning is a promising technology for biomedical applications. In this research project, a novel laser based marking method for toric contact eye lenses has been proposed. Toric contact eye lenses are designed to address general blurring that occurs due to uneven cornea which is known as astigmatism. Toric lenses have two powers in them, created with curvatures at different angles of cone. For proper functioning of toric lenses their orientation with respect to eye is critical. So toric lenses are manufactured with some form of marking which helps in deciding the orientation with respect to eye. The proposed method is to use the principle of laser interferometry in marking the metal inserts which will subsequently be transferred to lens surface during injection molding. For the research project stainless steel was selected as the material from the commonly used materials for the lens inserts. The marking of stainless steel with respect to different laser parameters (e.g. peak pulse power, rep rate, polarization and marking time) was studied. Mathematical modeling has also been done to predict the effect of aspherical curvature of lens insert on marking parameters and to study the effect of laser interference on the marking quality and quantity of stainless steel. The proposed marking method will not only reduce the marking area on the toric lens but also increase the visibility of the marking. In addition, using the principle of interference in marking reduces the amount of laser energy required for marking which reduces the heat affected zone thereby increasing the life of high value added metal inserts