Intraocular surgery is the most commonly performed refractive surgery procedure in the world, with increasing numbers of patients being able to benefit from the life-changing procedure. Each year approximately 16 million procedures are carried out. Regular advancements in IOL technology, optics and design have occurred in the decades since the procedure was first carried out, and such developments continue to this day.
Traditionally, IOL surgery has been performed on patients with “mature” or “advanced” cataracts which impair the patients’ vision. By removing the cloudy natural lens and replacing it with a clear implant, distance vision is restored. Clarity of vision is improved and colours instantly appear more vivid. The patient is, however, left dependent on spectacles for all near vision tasks, including reading.
Modern IOLs, in addition to correcting for distance vision, now also incorporate near vision prescriptions, thus helping patients be less dependent on reading spectacles. Patients no longer need to wait until a cataract has formed or matured to seek treatment. One type of lens that has proved successful in recent years is a Multifocal IOL. This lens has different visual zones focussing at different focal distances. These lenses refract and diffract light into different focussing distances. This lens has had amazing results, and most people can see to read newspaper size print without the need of reading specs.
An alternative to the Multifocal IOL is the Accommodative lens. This implant works in a similar way to the natural lens. It works by moving forwards and backwards as the eye naturally focuses and gives great mid-range/intermediate vision as well as good distance vision. This lens is particularly effective for patients who frequently use computers.
The material from which implants are made has also changed from a more traditional, rigid material such as PMMA to more flexible materials such as silicone and acrylic. The Accommodative IOL requires such material for its mobility. The flexibility of IOLs is also advantageous in surgery in that a much smaller incision is now required (~3mm) than previously (~9mm). Furthermore, micro incision lenses are also being developed to fit through even smaller incisions (1.5-2mm), therefore avoiding the need for stitches and requiring a shorter procedure time. (~30min).
Monofocal IOLs continue to provide patients with good distance vision, and there have also been advancements to these. Aspheric IOLs are now used, which are very similar in shape and design to the natural lens. These provide clearer, sharper vision than more traditional spherical monofocal IOLs, which can result in loss of clarity and glare/starbursts.
About 20% of patients wanting refractive surgery have moderate to high levels of astigmatism. In the past, only small levels of astigmatism could be corrected, but now using different surgical techniques and Toric IOLs, higher levels of astigmatism can be corrected (up to 12 dioptres). Piggyback IOLs can also be used as a secondary procedure to correct astigmatism following earlier cataract surgery.
For younger patients as far as IOLs are concerned, the Phakic IOL or Implantable contact lens is available. The Phakic IOL is an iris-supported lens which corrects distance vision. The accommodative features of the natural lens is utilised and the patient can see all distances perfectly clearly. Phakic IOLs are regularly used if a patient is unsuitable for laser vision correction. This often includes patients with high prescriptions or thin corneas.