The cataract is due to the opacification of the crystalline lens, which is a kind of magnifying glass of 9 mm in its diameter and 4 mm thick, situated just behind the pupil. The pupil is the black hole exactly in the middle of the iris, thin round curtain that gives to the eye its colour.

Normally, this lens is transparent like crystal -thus its name- ; it gives the eye the third of its optical power ; the two other thirds are offered by the cornea, strongly convex porthole ; so that the images can focus onto the retina.

The causes of the opacification of the cristalline lens are not yet all known, and gather throughout the life : thus the cataract appears usually when one becomes older. Can be mentioned : diabetes mellitus, certain feeding errors, too much sun exposure, smoking addiction, violent and direct ocular trauma, some drugs, rare genetical diseases.

The only effective treatment of cataract is surgery, which must be done when visual acuity becomes low and disabling. On principle, when the patient drives, it is forbidden to operate over 20/50 with optimal optical correction ; and when patient do not drive, the surgeon decides to operate when reading becomes difficult.

Most often, the operation is performed under local anesthesia, with eyedrops and without injection, after sedation by a hypnotic tablet, and lasts half an hour, during which one -of course- does not feel anything. The surgeon removes the ill natural lens, which is no more optically effective, and moreover makes a shield to vision ; and replaces it by an artificial plastic lens -we often call "implant"-, the power and the size of which are precisely determined according to each case.

The technique is most often mechanical (phako-emulsification with ultra-sounds), sometimes manual when the cataract is too hard. The intra-ocular artificial lens lasts all the patient's life ; there is no "rejection", neither recurrence of the disease.

If we can consider nowadays that this very frequent surgery gives excellent results (more than 95%), cataract surgery, like every human enterprise, still contains a small part of risk : the rate of failure or complication is relatively low, but exists (infection, for example). Here is the reason why one should not consider it is a trite operation, with a guaranteed result.

This surgery is usually ambulatory. The eye during the following days is not painful ; one can only feel a tiny irritation, with a slightly red eye. The post-operative treatment consits only in eyedrops, and lasts 2 months in the average, during which one must schedule consultations with one's ophthalmologist, especially in the early follow-up.

The visual benefit seems more rapid when the cataract was advanced ; often patients are delighted as soon as the following day. In fact, the maximum recover is obtained in approximatively one month, after what most often one must decrease the optical power of one's spectacles.