How Soft Contact Lenses Were Invented Using Hydrogels

This patent describes the chemical recipe for soft, water-absorbing plastic materials that form the basis of modern soft contact lenses.

What it covers

The patent defines a shaped body made from a hydrogel, which is a material that holds a large amount of water. It uses a base of a water-soluble monoester (like hydroxyethyl methacrylate) mixed with a small amount of a diester to create a cross-linked structure. This cross-linking acts like a microscopic net that holds the water inside the polymer without the material dissolving. By adjusting the ratio of these ingredients, the resulting plastic remains soft and flexible while retaining its shape in an aqueous environment.

What it doesn't cover

• —Does not cover rigid gas-permeable contact lenses made from non-hydrogel materials.
• —Does not cover non-cross-linked polymers that would simply dissolve in water.
• —Does not cover the specific manufacturing process of spinning or molding the lenses, only the chemical composition of the material itself.

The clever bit

The inventors realized that by adding just a 'minor amount' of a cross-linking diester to a hydrophilic polymer, they could create a stable, water-swollen solid that wouldn't wash away, effectively trapping water within a plastic matrix.

Why it matters

This invention transformed vision correction by replacing hard, uncomfortable plastic lenses with soft, breathable alternatives. It is the foundational technology for the entire soft contact lens industry, which serves millions of people worldwide.

Real-world examples

• 1.Soft contact lenses
• 2.Hydrogel wound dressings
• 3.Drug delivery implants