Your Guide To Understanding Types Of Cataracts
Cataract is a clouding of the lens, convex lens dioptric power in variable located inside the eyeball. It is the most common cause of visual impairment in adulthood-senile in the world. Cataracts as a disease entity has been known for thousands of years. Nevertheless, until the middle of the seventeenth century we assumed that cataract was a clot “rotten mood” behind the pupil, can block the enactment of the spirit of vision from the eye, thus interfering with the view. Cataracts can occur at any age: the classification of this disease is performed based on the age of onset and the presence of factors that may have caused the onset itself, they speak of congenital cataract, senile cataract, cataract complicated cataract and secondary.
Feature prince of the lens, together with the accommodative capacity, is the trasparenza.La cataract is just a loss of this characteristic. The haze is caused by an alteration of the submicroscopic structure of the components of the lens. The theories arose to explain this pathological phenomenon or, rather, pathophysiological (more than 2 out of 3 eyes undergo opacification above the age of 65!), Are numerous, some even contradictory. The known risk factors are age, diabetes mellitus (the incidence of cataracts in patients with diabetes is three times higher than non-diabetics), trauma, bulbar, the long-term cortisone therapy, heredity (evident in congenital cataracts ).
Types of Cataracts
It is characterized by visual disturbances that may have evolved more or less quickly and be more or less disabling depending on the different types and maturation stages of cataract:
- Visual impairment:
It is the symptom that most frequently arises in alarm and causes the patient to undergo eye examination. The reduction in visual capabilities typically evolves in a slow, over months or years, in senile cataracts.
This disorder is very serious vision for bilateral congenital cataracts, where it can lead to amblyopia ex anopsia. Cataracts, in itself, never leads to blindness.
- Monocular diplopia:
It consists of the ghosting fixed with the eye with cataracts. May be present in the initial stages, where the irregularity of the fibers lenticular determines a diffraction of light rays resulting in vision of two or more images, even when it is occluded the contralateral eye.
In nuclear cataract is a frequent miopizzazione (progressive myopia index) that can reach even the value of many diopters; often in the initial stages, the miopizzazione is not accompanied by loss of transparency which, with its correction, you can get a visual acuity equal to 10/10. In parallel, in the elderly, there is a progressive reduction of presbyopia. More rare and always mild, astigmatism and hyperopia are secondary to changes in refractive index at the level of cortical fibers.
The opacity act as a filter by changing the transmission of different wavelengths which leads to a dyschromatopsia, mainly for blue and violet, and then a subjective sensation of seeing the objects around yellowed.
- Reduction in contrast sensitivity:
in some patients, although the retention of a good visual acuity, you have obvious subjective disturbances, secondary to the reduction of the quality of the view. The test of contrast sensitivity can be helpful and sometimes is more reliable than the change in visual acuity to assess the development of cataracts in the early stages of the disease.
Glare and halos around lights of vision:
More frequent in the anterior cortical cataracts, is secondary to the increase in light scattering that occurs at the edge of the opacity.
- Narrowing of the visual field:
The opacity devices, when they are particularly dense, acting as a diaphragm resulting in a narrowing of the visual field. Also cataracts, resulting in a reduction of the intensity of the stimulus light that reaches the retina, determines a concentric narrowing of isoptere. This presents difficulties in the differential diagnosis when, in the presence of a person with cataracts and glaucoma, we must determine which of the two diseases can be attributed the deterioration of the visual field.