In 1949, British Ophthalmologist Sir Harold Ridley successfully implanted the first intraocular lens (IOL) at St. Thomas Hospital in London. The implant was made of an inflexible material called PMMA (polymethylmethacrylate), which Ridley thought to use after observing the eye’s tolerance of PMMA following eye injuries in Royal Air Force pilots. When the pilots’ plastic canopies were struck with bullets, they shattered, leaving small pieces of PMMA in the pilots’ eyes. Ridley observed, however, that the pilots’ eyes were compatible with and did not reject the inert PMMA substance. This inspired him to use PMMA in early IOL implantations. More recently, however, softer materials such as silicon and acrylic have regularly been used for the procedure, which allow for a smaller incision.
Despite Ridley’s success, the technique did not catch on in the wider ophthalmic community for a number of decades, as many were adverse to the idea of replacing the eye’s natural lens with an artificial one.
During the years since 1949, however, IOL technology continued to advance. In 1951, Ridley presented his paper ‘Intra-Ocular Acrylic Lenses’ at the Oxford Ophthalmological Congress, which was met with significant opposition from Ridley’s professional colleagues. Furthermore, Ridley’s work was condemned as reckless the following year, at the American Academy meeting in Chicago. 1952 also marked the first successful IOL implantation in the United States.
After years of progress, as Ridley and others continued to work to refine the surgery, the first international symposium on intraocular lenses and implants was held in 1966 at the Royal Society of Medicine in London. Through this, the Intraocular Implant Club (IIC) was formed, with Ridley as the first President.
There are two types of IOLs used in treatment: phakic and pseudophakic. The root of both words comes from the Greek word ‘phakos’, meaning lens.
A pseudophakic IOL replaces the patient’s own crystalline lens. The human lens is normally a biconvex, transparent structure that focuses light onto the retina. The curvature of the lens in young adults can be adjusted by eye muscles to focus objects at different distances. This effect is termed accommodation. Historically, the replacement of the patient’s crystalline lens was done for the sake of distance vision and/or to provide clarity from cataracts. Unfortunately, in gaining distance vision through a pseudophakic IOL, the patient had to sacrifice their accommodation effect. Today though there have been advances in the types of intraocular lens available to mean that vision at distance, intermediate and near can be improved.
The most common reason for using IOLs is to perform a cataract procedure. It has been routinely performed since the 1970′s, when IOL techniques finally gained widespread acceptance. The word cataract comes from the Latin ‘cataracta’ meaning ‘waterfall’ and describes a clouding or opacity that has formed in the patient’s lens. Cataracts are mainly caused by advanced age. Long-term UV exposure, secondary effects of diabetes and genetic factors are all attributive causes, however. Once the clouded lens has been removed and replaced with an IOL, the cataract will not reoccur. Over 14 million cataract procedures are performed annually across the globe.
Since 1999, phakic IOLs have also been available, and differ from pseudophakic IOLs as the lens is inserted in front of the patient
own crystalline lens. This allows for accommodation while correcting the distance prescription, and can correct for myopic, hyperopic, and astigmatic errors.
The choice of the IOL to be implanted is determined by the surgeon, and may depend on the medical history of the patient as well as other factors such as lifestyle and visual expectations.
Particularly high prescriptions are often corrected using pseudophakic IOLs. This procedure is termed a refractive lens exchange (RLE) and is typically performed on patients over the age of forty. The procedure is similar to cataract treatment, and takes around thirty minutes to perform.
IOL technology continues to develop, with increasing numbers of patients undergoing surgery to correct refractive errors and provide relief from cataracts each year.
The procedure has came a long way to mean that patients are treated now under a local anaesthetic meaning that the visit to the clinic is an out-patient basis and they can return home the same day. Visual recovery tends to be very quick with many patients achieving an excellent level of vision as soon as the day after the procedure.