Cataract is an ocular pathology consisting in the progressive opacification of the crystalline lens, that is the biconvex natural lens inside the eye that refracts light to bring an object into focus. An image is perceived as distorted because of blurred vision. It is a common age-related disease affecting more than half of people over 60 (senile cataract), but it can also show up after birth or in the earliest years of life (congenital cataract), after an eye injury or severe trauma (traumatic cataract), in diabetics, after an excessive exposure to sunlight (secondary cataract) or in those people who are affected by other eye diseases or who have used cortisone or chemotherapy drugs (drug or disease-related cataract). Cataract is the main cause of blindness or visual deterioration all over the world.

When does cataract occur, what are its symptoms and how to diagnose cataract
Cataract gradually develops causing no pain or changes in the eye appearance. The most common type is senile cataract, which manifests itself in people over the age of 60 and affects both eyes (bilateralism of the disease), but usually one eye is affected earlier than the other.

The most common symptom is blurred vision (visual acuity reduction). 
Another frequent symptom is sensitivity to light, sometimes associated with dazzle from lights and the perception of halos around light sources (dazzle and halos). Colours appear less vivid (dyschromatopsia), one can suffer from double vision (monocular diplopia) and in many case myopia (refractive errors) can occur (or increase, if already present) which, in the third age, cancels presbyopia: the elderly can “inexplicably” read without eyeglasses, suggesting an improvement however to be considered as transitory, since the visual impairment develops over time.

The cataract must be diagnosed by a qualified eye specialist after a complete eye examination, which includes determining visual acuity from far to near, examining the crystalline lens through a slit lamp with dilated pupil, tonometry and retinal examination to evaluate the opacification of the crystalline lens and exclude other corneal or retinal pathologies, which may cause the same decrease in sight.

Treatment of cataract
There are no medication, diets or glasses able to reverse cataract development. The only effective and permanent treatment is cataract microsurgery, which can be performed independently of the crystalline lens opacity level, when the cataract prevents the patient from carrying out everyday tasks and activities. After surgery, the chances of visual improvement are excellent (more than 97%); however, even though the surgery has been successful, the presence of other eye diseases may compromise the final result.

The modern cataract surgery removes cataract by replacing the opacified crystalline lens with an artificial one, made of plastic. The most widely used technique in the world is Phacoemulsification, a non-traumatic method that removes the crystalline lens after fragmenting it with ultrasounds, granting excellent results.