Multifocal Contact Lens Cast Moulding with Segmented Inserts
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Solution Overview
Problem
Existing methods for manufacturing multifocal contact lenses, such as those described in Patent Application WO 01/44860 A1 and US 5 611 970 A1, do not effectively utilize a mould insert formed in two parts, which limits customization of curvature and integration of features like truncation and forwardly projecting ledges for comfortable translation on the eye.
Innovation Solution
A method of cast moulding a translating multifocal contact lens using a two-part mould insert, where one part forms the anterior face with customizable domed surfaces for distance and reading vision, and the other part forms the posterior face with a standard curvature, allowing for precise curvature customization and integration of truncation and forwardly projecting ledges for comfortable lid engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional single-part mould insert is used, then the manufacturing process is simpler, but the customization of curvature and integration of features like truncation and forwardly projecting ledges is limited
Solution Approach 1:
The mould insert is divided into two separate parts: a first mould insert forming the anterior face with customizable domed surfaces for distance and reading vision, and a second mould insert forming the posterior face with standard curvature. This segmentation allows independent customization of each surface while maintaining manufacturing feasibility.
2Ease of operation
If existing manufacturing methods are used, then the process is straightforward, but the production of lenses with optimized lid engagement features is not achieved
Solution Approach 1:
The first mould insert is pre-configured with the domed surface geometry that incorporates both distance and reading vision zones, along with the truncation and forwardly projecting ledge features. This preliminary design of the mould insert ensures that the lens is formed with optimized lid engagement characteristics from the manufacturing stage, eliminating the need for subsequent adjustments or modifications.
3Manufacturing precision
If a two-part mould insert is used, then customization of anterior and posterior curvatures is enabled, but the moulding process becomes more complex
Solution Approach 1:
The mould system is segmented into two independent inserts: the first mould insert for the anterior face with customizable domed surfaces, and the second mould insert for the posterior face with standard curvature. This segmentation enables precise control over each surface's geometry while keeping the overall process manageable through modular design.
Solution Approach 2:
The first mould insert is designed with locally varied curvature characteristics - a domed surface with different optical zones for distance and reading vision. This local quality variation allows precise customization of the anterior face geometry to meet specific visual requirements while the posterior face maintains a standard curvature for consistent fit.
Data Source
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AI summary
There is provided a contact lens (60) which is produced by cast moulding. The cast moulding is achieved by the use of an anterior face mould insert (30) which has a cap (24) with a domed surface (26) and a body (10). The domed surface has provision for a distance vision segment (31 ) and a reading segment (32) separated by a demarcation (33). Further, the cap (24) has a cutaway portion (20) for producing a lower ledge and the body (10) has a projection (18) for producing a lower truncation in the resultant lens. Means is also described for forming a posterior face of the contact lens (60).