Both rod and “button in a bag” methods are used for acrylics, which are thermally cured in temperature-controlled water baths (molded or semi-molded IOLs are UV cured). These are usually formed from molded rods or, alternatively, “buttons in a bag” (a technique pioneered and developed by John McGregor OBE, founder of Contamac Ltd) in which a plastic envelope with cavities for each button is filled with acrylic monomer. These are usually 12.7- 15.0 mm in diameter and 2.5 to 3 mm thick (essentially the size of shirt buttons). The machining process is smaller in scale but no more complex than CNC machining operations in other industries. Machining (lathing and milling) enables specialist designs and customizations to be made for lower volumes or demands.

For mass production of lenses, molding technology is preferable, but limits the range of powers and geometries available to those of the available mold insert.

Hydrophobic and hydrophilic materials are commonly used and must be either machined or molded. Softening an acrylic or making it flexible and suitable for micro incision techniques, can be done in two ways: by adding water-loving components to the matrix or by adding monomers that relax the matrix bonds. Precise temperature control is vital to ensure that the resultant materials have the necessary properties. These techniques brought affordable cataract surgery to thousands. Russia’s Fyodorov Eye Institute (MNTK) pioneered radical mass implantation surgical techniques for public health hospitals across the country, as well as in the UK’s National Health Service (NHS). This breakthrough led to the development of implantable devices made of PMMA.

Remarkably, this plastic came to ophthalmology by chance when Harold Ridley (of Rayner fame) discovered its biocompatibility properties after splinters of aircraft canopies were found in pilots’ eyes without subsequent infections. You may know it by trade names such as Plexiglas or Perspex. PMMA is a rigid material widely used in transparent screening applications for example, in aeronautics, aerospace, and electronics. These lenses were originally made out of silicone or, more commonly, poly(methyl methacrylate), or PMMA. Let’s start by looking at the materials used to produce IOLs. Intraocular lenses (IOLs) and specialist contact lenses have been around for years, with new designs released on a regular basis, but have you ever thought – really thought – how lenses are actually fabricated?

Iol cut off wavelength