Cataract is an eye disease in which the natural lens of the eye becomes cloudy or thick, causing visual impairment.
It usually affects older people as an age-related change of the lens, but can sometimes occur in younger people too.

Treatment usually involves surgery to remove the cloudy lens and replace it with an artificial lens. Implantable plastic lenses, also known as intraocular lenses (IOLs), are available in different types for different purposes and to solve various vision problems. They are implants placed inside the eyeball, which - unlike contact lenses - remain inside of the eye, usually in the so-called lens bag, for the rest of the patient's life. Early detection and treatment of cataracts is important to prevent vision loss.

Cataract surgery involves the removal of an opacified or thickened lens and the implantation of an artificial lens. The surgery is usually performed under local anaesthesia through a small incision in the cornea, then using an ultrasound device. The procedure is a quick and effective outpatient surgery. After cataract surgery, patients experience a significant improvement in their vision and post-operative rehabilitation is usually quick and painless. However, a thorough eye examination before surgery and adherence to post-operative instructions are important to achieve the best results and minimise complications.

Implantable lenses for the human eye, also known as intraocular lenses (IOLs), are produced in different types, which serve different purposes and address various vision problems. Some of them are:

1. Monofocal lenses: these are the most commonly used lenses, offering only one focus point, usually for distance vision. Eyeglasses or contact lenses must be worn after surgery to ensure sharp vision at near distance (eg. reading).

2. Toric lenses: these special lenses correct astigmatism ("cylinder" refractive error), a visual defect caused by the distorted shape of the cornea. They help to achieve clear vision at both near and far distances.

3. Multifocal lenses: these lenses contain multiple focus points, therefore resulting as a correction of distance and near vision. As a consequence, patients are often less dependent on glasses after surgery.

4. Enhanced depth of focus (EDOF) lenses:
These lenses are made with an improved depth of focus to provide a wider range of sharpness than monofocal lenses. Enhanced depth of focus lenses provide a good visual experience at both distance and intermediate ranges, but do not provide complete spectacle-free vision. Reading glasses may be required for close-up, detailed work or reading small printed characters.