A great effort has been made to develop technologies for cast molding of hydrogel contact lenses with high precision, fidelity and reproducibility and at low cost. One of such manufacturing technologies is the so-called Lightstream Technology™ (Alcon) involving reusable molds and curing a lens-forming composition under a spatial limitation of actinic radiation (U.S. Pat. Nos. 5,508,317, 5,583,163, 5,789,464, 5,849,810, and 8,163,206), which are incorporated by reference in their entireties. The Lightstream Technology™ involves (1) a lens-forming composition, (2) reusable molds produced in high precision, and (3) curing under a spatial limitation of actinic radiation (e.g., UV/Visible light). Lenses produced according to the Lightstream Technology™ can have high consistency and high fidelity to the original lens design, because of use of reusable, high precision molds. In addition, contact lenses with high quality can be produced at relatively lower cost due to the short curing time and a high production yield.
Modern high-volume mass production process for medical devices like contact lenses utilizes re-usable molds in each production cycles. The conventional re-usable contact lens mold consists of a quartz convex base curve and a glass concave front curve. The base curve mold is composed of individually ground and polished quartz, while the front curve mold is composed of high precision press mold and polished glass. However, hydrogel contact lens production in curing under a spatial limitation of actinic radiation with Lightstream Technology™ may produce flash along lens edge due to lens forming material left in gap between base curve mold and front curve during curing under a spatial limitation of actinic radiation. Furthermore, when manufacturing UV absorbing contact lenses in the Lightstream technology, the lens edge quality issues (flash) become more severe than when manufacturing non-UV absorbing contact lenses.
Therefore, there is a need for new reusable molds for front curve mold that can produce lens with clean cut lens edge (no flash).