Anyone who wears contact lenses often must have encountered some troubles. The lenses are so flimsy in your hands that they collapse on your fingers before your eyelids open, and then you have to repeat the process again and again.
Even if you are an experienced user, you can’t do anything with these flimsy lenses. How important it is to find a pair of “firm and shapely” contact lenses, to avoid the pain of blinking countless times every day.
So, what exactly makes lenses “floppy”? But some lenses are so stylish that they stay in place for as long as they are in a bowl. Ultimately, the manufacturing process is different, and the different growth environments create different “character traits” in corneal contact lenses. So, what is the “growth environment” of contact lenses?
Contact lens process
Common contact lens manufacturing methods include centrifugal casting, turning, dry mold casting, stable soft mold casting, and integrated molding.
Centrifugal Casting Process
It is the first method used for the commercial production of soft lenses. By centrifugal casting, as the name suggests, the lens polymer is injected in liquid form into a rotating mold and rotated at high speed using centrifugal force.
Advantages: the centrifugal casting method is an economical manufacturing method, with low production costs, high efficiency, good reproducibility, soft lenses table = smooth surface, and the ability to produce very thin and comfortable lenses.
Disadvantages: low modulus of elasticity of the lens, poor formability, not easy to handle, and poor ability to correct astigmatism.
The turning process is widely used in the production of PMMA lenses, RGP lenses, and soft lenses.
Advantages: the turning process allows for to personalization of the lenses, such as the production of astigmatic presbyopia lenses, etc. It processes lenses with good formability, is easy to handle, and can correct astigmatism to a certain extent.
Disadvantages: however, the process is costly and cannot be used for mass production, such as discarded or frequently replaced lenses, while the processing error is slightly larger and slightly less repeatable.
Dry mold casting process
The dry die-casting process places the liquid material monomer between two molds (mother and child) and allows it to polymerize to form the desired shape.
Advantages: low production costs, high efficiency, mass production of disposable lenses, good repeatability, good formability, easy handling, and correction of a certain amount of low astigmatism.