A cataract is a progressive loss of transparency of the lens. This process, linked to phenomena of oxidation of proteins that constitute it, is the result of a biochemical phenomenon that occurs with increasing age. The increase in life expectancy has led to an increase in the number of cases, so that today the intervention of cataract removal is one of the most performed in all hospitals in the world.
Although this is a typical disease of senescence, may also be less advanced age, but in these cases it is linked to cataract secondary factors (diabetes, inflammation, excessive exposure to ultraviolet or infrared radiation, congenital and iatrogenic causes).
Symptomatology and classification
The symptoms are generally characterized by a blurring of vision overall, but the visual impairment is more evident as larger and more intense is the clouding of the lens. Therefore, ophthalmologists classify cataracts according to their position within the layers of the lens, but from the practical point of view it is more useful to classify them according to age of onset:
- Senile cataract is the most common form, linked to the slowdown of the biochemical processes that maintain the transparency of the lens. After 65 years it is normal to slightly yellowish discoloration of the nucleus of the lens, which is often not perceived subjectively; this coloration becomes more intense (nuclear cataract) which, in the initial stages, can determine the appearance of a myopic refraction due to the increase of the index of refraction of the core itself. It happens in this case that the presbyopic patient noted a real improvement in near vision, to the point of being able, at times, to abandon the use of glasses for near vision. In other cases a "sanding" of the back sheet of the crystalline lens (posterior subcapsular cataract) which leads to a decline in visual that may, in time, become total.
- The juvenile cataracts appear at a younger age, but it usually is related to a problem of metabolism such as diabetes mellitus, or skin diseases. Although many diseases of other structures of the eye such as uveitis or glaucoma can give a cataract as a result.
- Congenital or infantile cataract is present at birth or develops in the first few years of life as a result of metabolic diseases such as galactosemia or rheumatic as juvenile rheumatoid arthritis. These cataracts interfere with the development of the function of the view, still immature and the eventual implantation of an artificial lens in the eye still growing poses serious problems and in any case involves the loss of the power of accommodation of the eye concerned.
The total cataract makes it virtually blind and you need to intervene surgically replacing the clouded lens with an artificial intra-ocular lens, located behind the iris. In the past they had been marketed eye drops designed to slow down the process of opacification of the lens, but in time these products have not demonstrated a real clinical efficacy.
The surgery, phacoemulsification defined, takes place in most cases an outpatient, under local anesthesia, obtained by instilling anesthetic eye drops a few minutes before the surgery. After practicing a circular opening in the anterior capsule of the lens (the width of the cut has gradually been reducing over the years, thanks in part to the production of artificial crystalline leaflets, which are inserted into the eye with an injector), the nucleus of the lens is crushed by the surgeon using an ultrasound probe ("phacoemulsificator"), which resulted in the reduction of response times; However, as the cataract is "ripe" (ie, more is at an advanced stage), plus the lenticular nucleus becomes hard and the surgeon takes more time in the process of phacoemulsification.
Then if the lens has become particularly opaque and has increased its hardness, the intervention by the method described above phacoemulsification may not be appropriate in these cases, but now increasingly rare, cataracts should be operated with extracapsular extraction methods already in use a few years ago. These methods do not lead to decreased visual acuity compared to the intervention performed with phacoemulsification, but require a longer healing time because the surgeon must make an opening wider than the eye takes longer to heal higher.
The lens capsule, completely emptied, it is still used for the insertion of an artificial lens that can also go to compensate a defect of view of pre-existing (myopia, hyperopia or astigmatism); vision, however, is monofocal, so the patient will still have to wear glasses to correct distance vision or near. They were introduced in the market for some years now, intraocular lenses are capable of correcting the vision from both distance and near. These multifocal lenses are not currently reimbursed to the national health system.
The opening of the cornea is usually very small (around 2 mm), and is not necessary for the application of sutures. After the surgery is necessary to protect the bulb from trauma, and infections from excessive light and the instillation of eye drops with antibiotics, steroids and mydriatics.
The cataract surgery does not involve particular risk, although not always gives positive results, and there are patients who have not recovered more the view, but has a success rate of over 95%. The high pressure liquids that are introduced into the anterior chamber of the eye (a very small space of about 2.5 mm), however, can cause accidental breakage of the posterior capsule with vitreous loss and consequent edema of the cornea, retinal detachments, macular edema .
A complication that sometimes occurs is the opacification of the posterior lens capsule work. This phenomenon, called secondary cataract, can be explained as a reaction to a foreign body (the artificial lens) and can be quickly eliminated with application of a YAG laser.
The replacement of the natural lens, which has a physiological curvature, with a flat lens, determines a forward displacement of the vitreous and a consequent traction of the retina that can give rise to breakage or detachment of the retina, the more frequent the closer the subject is shortsighted .
More serious, although rare, infectious complications, which represent an indication for reoperation immediately, before the seeds have reached the retina causing irreparable damage.