How are contact lenses made?

The principle of using lenses directly on the surface of the eye has been around for many years, but the use of contact lenses has only become popular in about the last 40 years. The reason for this is that manufacturing contact lenses was traditionally very difficult. However, breakthroughs in materials and manufacturing over the past 70 years have made contact lenses more available, to the point that, in the present, they easily rival traditional eyeglasses in terms of the number of wearers.

The first contact lenses, produced in the late nineteenth century, were made of glass and were blown by skilled glassblowers. However, because they restricted oxygen flow to the eye they tended to be uncomfortable, and the vision corrective properties were difficult to standardize. 

The discovery of a useful plastic material called polymethylmethacrylate in 1934 meant that lenses could be cast molded, which is a process that involved using the eye as a cast while moldable plastic was placed on it. The resulting mold was used to make lenses – but these were still impermeable and thus uncomfortable.

Today, most contact lenses are created using a process known as spin casting. The material used to make the lenses is placed in a mold, and is then spun around at high speed. This process spreads the material evenly over the surface of the lens. The materials used vary from fluorosilicone acrylate material for rigid gas permeable lenses to materials such as Bausch & Lomb's polymacon for soft contact lenses, but all of these now have excellent oxygen permeability for greater comfort and eye health.