Cataracts tend to occur in people over 50 years old and they are more common with advancing age. A cataract occurs when the natural clear lens of the eye becomes cloudy. It has the same effect as having a dirty lens in a photographic camera. Cataracts usually are the result of "natural" age related changes in the clear lens of the eye. They are slowly progressive and unless they actually affect the person's vision, there is no need to do anything about them. A common early manifestation is a change in the prescription of their glasses.

There is no absolute level of vision where a cataract 'needs to be done'. In the vast majority of cases, cataract surgery is a very low risk procedure with the chance of serious complications being less than 1 in 1000 cases. If the patient feels that the benefit of improvement of vision with cataract surgery justifies that small risk, the patient can be assessed for surgery. Regarding the level of vision for cataract surgery, this is a subjective mater and it largely depends on the patient. For example, an early cataract may cause no significant problems to a pensioner who does not drive but the same type of cataract may cause a lot of vision problems for a taxi driver, who does a fair bit of night driving.

Modern cataract surgery is very comfortable and it only takes about 10 minutes on average. The cataract is removed using ultrasound through a very small key hole  and it is replaced by an artifical lens. No sutures are required. Modern eye measurement and lens technology allows surgeons to remove the need for distance glasses following cataract surgery.

Some lens designs also allow for both distance and near vision without glasses. Lens choice and suitability depends on many factors and this is part of a customised assessment for the particular patient. Modern lens implant technology allows for correction of shortsightedness (myopia), longsightedness(hyperopia), astigmatism and even presbyopia (so that patients can be less dependent on glasses for both near and distance vision). Suitability for presbyopic lens implants depends on the requirements of the patient and the state of health of other parts of the eye.

This is an educational video by the European Society of Vitreoretinal Surgeons