Definition

Cataract is a disease that affects one in four people after the age of 70 and is the most frequent cause of low vision in adulthood. It consists of a clouding of the lens, the biconvex lens with variable dioptric power placed inside the eyeball.
The classification of this pathology is carried out according to the age of onset and the presence of factors that may have determined it: we speak of congenital cataract, senile cataract, complicated cataract and secondary cataract.

Symptomatology

The symptomatology is characterized by visual disorders that can have a more or less rapid evolution and be more or less disabling depending on the different types and stages of maturation of the cataract:

• visus reduction: this is the symptom that most frequently alarms the patient and causes him to undergo an eye examination. The reduction in visual abilities typically evolves slowly, over months or years, in senile cataracts;
• monocular diplopia: consists of the splitting of the images fixed with the eye with cataract; it can be present in the early stages, where the irregularity of the lenticular fibers determines a diffraction of the light rays with consequent vision of two or more images even when the contralateral eye is occluded;
• In the nuclear cataract there is frequent progressive myopia (index myopia) that can reach the value of many diopters; often, in the early stages, myopia is not accompanied by loss of transparency so that, with the relative correction, it is possible to maintain a discrete visual acuity;
• in the elderly, there is a progressive reduction in presbyopia;
• other typical visual disorders of cataracts are: dyschromatopsia (alteration of color vision), reduced contrast sensitivity, glare and seeing of halos around the lights, narrowing of the visual field.

In the presence of unilateral cataract, even if the visual acuity is compensated by the healthy eye, there are problems of limitation of the visual field, photophobia and reduction of the stereoscopic sense.
Known risk factors are age, diabetes mellitus (the incidence of cataract in diabetics is three times higher than in non-diabetics), eye trauma, long-term cortisone therapies, heredity (evident in congenital cataracts)

Diagnostics

The  diagnosis of cataract  is made by the ophthalmologist who, after a complete examination of the eye, can determine if any reported disorders are actually derived from an opacity of the lens and if, therefore, surgery is necessary.
In adults, the fundamental motivation that leads to cataract surgery is the reduction of visual acuity.
The extent of this reduction is variable and is a function of the visual needs of the individual; in general, in the presence of unilateral cataract, the intervention is indicated when the visual reduction is such as not to allow the normal performance of the patient's daily activities.

Therapy

The only effective treatment for cataracts is surgery. Every year 500,000 cataract surgeries are performed in Italy. Today the most widely used surgical technique in cataract extraction is phacoemulsification.

The cataract lens is replaced with an intraocular lens (IOL) that allows the correction of the refractive error of the eye. Today there is also the possibility of implanting toric lenses (multifocal or pseudoaccommodative) for the correction of astigmatism, which partially restore the ability to focus of the eye in order to use glasses to read as little as possible after the intervention.
The intervention is generally carried out on an outpatient basis and can be conducted in various modes of anesthesia: under general anesthesia (e.g. newborns), local, intracameral and topical (with drops of anesthetic eye drops).Postoperative therapy consists of anti-inflammatory eye drops and antibiotics.

Recently, the use of femtosecond laser has been introduced in cataract surgery: this type of technology allows to perform some delicate phases of the operation by means of a femtosecond laser that replaces the surgeon's hand. The laser is guided by a computer that captures images of the patient's eye in real time, through optical coherence tomography (OCT).