Modern-day cataract surgery is one of the most common and successful surgical procedures performed worldwide. Our lens helps us see by focusing light onto the retina. A cataract is any opacity that develops in this naturally clear lens. If allowed to progress, the entire lens can become cloudy and white. When looking at an eye with an advanced cataract, the pupil (centre of the eye) is white instead of black. In the past, it was thought that this white appearance resembled a cataract, the white water seen as a waterfall cascades.

What is the earliest know form of cataract surgery performed?

An advanced cataract prevents light from entering the eye. The earliest known method of treating cataracts has been used since 500 BC. This technique, known as ‘couching’, used a needle to push the cataract out of the way and allow light to enter the eye. The immediate improvement in vision was offset by complication such as infection that resulted in blindness.

The next development in cataract surgery was described by the French surgeon Daviel in 1747. In extracapsular cataract extraction (or ECCE), the capsule (the structure that holds the lens in the centre of the eye) is punctured and the cataract is expressed from the eye through a large incision. This resulted in an improvement of vision in 50% of cases. Apart from a few decades in the 20th century when both capsule and cataract were removed together (intracapsular cataract extraction), extracapsular cataract surgery has been the preferred choice of treatment until the acceptance of phacoemulsification surgery. Today, ECCEs are performed with a small incision and improve vision in over 90% of cases.

Phacoemulsification was invented by the American ophthalmologist Kelman in 1967. The issue with other forms of cataract surgery is that the cataract is removed in one piece that requires a larger incision, sutures to close the incision and longer recovery times. Phacoemulsification uses ultrasound energy to break the cataract up into tiny pieces (in a similar to the treatment of kidney stones) that are sucked out of the eye. This means that a much smaller incision is required that heals quickly with no sutures required. The technology has advanced over several decades and now it is preferred technique for most ophthalmologists worldwide.

While the above techniques improve vision by removing the opacity, something is needed to replace the natural lens’ ability to focus light onto the retina. Before the invention of the intraocular lens implant (IOL), this was achieved with high-powered spectacles. The first IOL was implanted following cataract surgery by Ridley in 1949. This British ophthalmologist developed the IOL once he noted that World War 2 pilots tolerated shrapnel from plastic airplane windshields inside their injured eyes. Early plastic implants were large, rigid and required a large incision to introduce them.

Over the subsequent decades, evolving material science and manufacturing techniques has resulted in the large rigid plastic IOLs being replaced by smaller foldable plastic IOLs that can be introduced through an incision smaller than 3mm. A greater understanding of optics (the science of how light travels) had led to advances in lens design. Where a few decades ago, IOLs aimed to give excellent vision at a fixed distance, new IOLs such as toric IOLs can fix astigmatism (where cornea or the front of the eye is not perfectly round causing blurred vision) or give a good focus over different distances. These latter IOLs are known as premium or multifocal IOLs, and may be described by the technology that they use such as trifocal or enhanced depth of focus (or EDOF) lenses. Ophthalmic surgeons use them to allow patients to be less reliant on needing glasses to see.