Saturday, October 26, 2019

What Are the Types of Cataracts?

What Are the Types of Cataracts?
According to the World Health Organization (WHO), cataracts are the leading cause of blindness and visual impairment worldwide. With the general aging of the population, the overall prevalence of visual loss due to lenticular opacities increases every year

Types of cataracts

There are many qualitative methods for identifying cataracts, but the best known is the position of opacity of the anatomical lens, the posterior, nuclear or subcapsular cortical place. In order to evaluate each form of cataract, many forms of medical classification and technical criteria have been developed to assist the doctor

1. Morphological classification

Depending on the morphology (size, site and appearance), cataracts can be classified into capsular, subcapsular, cortical, supranuclear, nuclear, lamellar and sutural cataracts. Here the individual position and configuration of each type of morphological cataract is described

Capsular Cataract
The lens capsule can develop localized opacities in aging-related cataracts. However, they can also occur in uveitis in association with subsequent synechiae or secondary to lesions caused by drugs, radiation or trauma. Localized central capsular cataract (polar cataract) can occur in the anterior and posterior capsules. They are generally congenital, although they may also be secondary to trauma

Polar cataract is generally dense, localized and non-progressive. Since they are stable, many patients can tolerate them and can maintain good and adequate vision with conservative treatment (e.g. dilation of the pupil, sunglasses on bright days, optical correction)

Subcapsular Cataract
Granular opacities develop in the clear subcapsular area and are more commonly posterior subcapsular than the anterior. In this type of cataract, opacities usually develop for the first time and are more advanced in the posterior peripheral cortex, near the pole, and therefore often develop gradually in the anterior region. This opacity often begins as vacuoles which soon become confluent to give an uneven layer. This type of membrane opacity diffuses the light considerably and gives the impression of a densely opaque saucer-shaped region. The remaining bark was generally clear, but sometimes deeper opacities were present. In addition, nuclear sclerosis has often been observed
  • Posterior subcapsular cataracts (PSC) are often observed in younger patients than those with nuclear or cortical cataracts. PSCs are located in the posterior cortical layer and are generally axial. The first indication of PSC formation is a slight iridescent glow in the posterior cortical layers visible with the slit lamp. In the later stages, granular opacities and a plaque-like opacity of the posterior subcapsular cortex. The patient often complains of glare and bad vision in bright light conditions because the PSC further obscures the pupillary aperture when myosis is induced by bright lights, arrangements or miotics
  • Anterior subcapsular cataract Contrary to PSCs, anterior subcapsular cataract is made up of multiple layers of the anterior lens epithelium and the deposition of an abnormal lens capsule. Anterior subcapsular opacities are less common and in the early stage they are difficult to recognize on examination of the slit lamp. These opacities occur in glaukomflecken, Wilson disease, miotic therapy and the administration of chlorpromazine and amiodarone

Cortical Cataract
Contrary to nuclear cataract, cortical cataract is associated with the local alteration of the structure of mature fiber cells. Once the integrity of the membrane is compromised, the essential metabolites of the affected cells are lost. This loss leads to strong oxidation and precipitation of proteins. Cortical cataract is generally bilateral, but is often asymmetric. Its effect on visual function varies greatly, depending on the position of the opacification with respect to the visual axis

A common symptom of cortical cataract is glare from intense focal light sources, such as car headlights, and can also cause monocular diplopia. Cortical cataract varies greatly in their progression rate; Some cortical opacities remain unchanged for long periods, while others progress rapidly. Cortical opacities, especially in complicated cataracts, can also come from subcapsular opacities that appear inside the cortex as the lens grows and deposits new surface fibers on them

Supranuclear Cataract
Deep cortical cataract like congenital coronary cataract can be classified separately as supranuclear cataract. This cataract, also called cuneiform ~, Laract, is characterized by opacity, rays or wedge-shaped riders "; intermediate or internal cortex. These opacities are rounded in the outline and are associated with changes in the outline which may be white or cerulean. The opacity number gradually increases with the passage of time and interferes with vision: coronary cataract surrounds the nucleus like a crown and, since it originates during the embryonic development phase, it is located in the deepest layer of the cortex

Nuclear Cataract 
Congenital opacities are invariably nuclear in nature because there is no target cortex at birth. Congenital nuclear opacities occur in rubella, galactosemia and cataract polverulenta centralis where the entire embryonic nucleus is opaque. This cataract is characterized by the scattering of diffused light in the central part of the lens. This dispersion of light is homogeneous throughout the nucleus and opacities are generally not observed under a slit lamp microscope. Opacification is usually accompanied by pigmentation and consequently the absorption of selective resonance occurs within these pigments

Laminar (ZONULAR) Cataract 
Laminar cataract is invariably congenital and the most common type of cataract , since it involves a foil of the fetal or nuclear zones, so as to surround both the anterior and posterior lens, forming an apparent hollow disc.Such cases are generally bilateral and symmetrical and the opacification density can vary considerably. Less opaque lamellar cataracts may be compatible with good vision and require minimal medical intervention (eg. Optical correction, therapeutic mydriasis)

Sutural Cataract
Sutural or stellate cataract is an opacification of the V-sutures of the fetal nucleus. Generally it does not affect vision. These opacities often have branches or knobs that protrude from them. Bilateral and symmetric sutural cataracts are often inherited in an autosomal dominant pattern

2. Classification According to Maturity 

Cataracts have also been classified according to their developmental stage (mature, immature, etc.). These are:

Immature Cataract
Immature cataract is defined as one in which scattered opacities are separated by light areas. The target appears gray

Intumescent Cataract
In this type of cataract, the target is swollen by the incorporated water. It can be immature or mature. The anterior chamber becomes shallow

Mature Cataract
The lens can swell and swell quickly due to the rapid hydration of the lens cortex. Complete lens opacification is called mature cataract. In this type of cataract, the entire bark becomes opaque white. The outlines of the opaque fibers of the lens are visible. The vision is drastically reduced to the perception of only the movement of the hand

Hypermature Cataract
Hypermature cataract is a mature cataract that has become smaller and has a wrinkled capsule due to water leaking from the lens

Etiological classification
Etiological classification is ideally considered to be the most widely accepted cataract classification. Various types of cataracts in this classification are as follows

Congenital Cataract
The term congenital cataract refers to an opacity of the lens present at birth. Lens opacities that develop during the first year of life are called infant cataracts. Since lens opacities are difficult to detect at birth and are visible only on subsequent examination, many terms use these terms interchangeably. Congenital and infantile cataracts can be unilateral or bilateral. They can be classified on the basis of morphology, presumed or defined genetic etiology, presence of specific metabolic disorders or associated ocular anomalies or systemic results

Developmental Cataract
Developmental cataracts can occur from childhood through adolescence. Therefore, this cataract can involve childhood or adult nuclei, deeper parts of the cortex or capsule. These small opacities develop after birth at the time of deposition of newly formed opaque slow fibers. Developmental cataracts generally affect the particular area that is formed when this process is disturbed

Acquired Cataract
In acquired cataracts, opacification occurs due to the degeneration of the normal lens fibers already formed. The exact mechanism and reasons for lens fiber degeneration are not yet fully understood

Metabolic cataract
Diabetic cataract, galactosemic cataract, galactokinase deficiency cataract, hypocalcemic cataract (tetanic cataract), nutritional cataract, cataract in Wilson's disease, cataract in Lowe syndrome, cataract in Fabry's disease, cataract in Fabry, cataract in mannosidosis, cataract in myotonic dysfunction myotonic. hypothyroidism

Traumatic Cataract
Penetrating and non-penetrating physical injuries can cause cataracts. In younth, trauma is the most common cause of cataract. A blunt, non-perforating lesion can cause lens opacification as an acute event or as a late sequela. A concussion cataract can involve only a part of the objective or the entire lens. 

Often the initial manifestation of a concussion cataract is a star-shaped or rosette-shaped opacification (rosette cataract), usually axially positioned, which involves the capsule of the posterior lens. The size of the opening in the lens capsule determines the morphology of the cataract, in cataracts secondary to penetrating trauma. In some cases, blunt trauma causes dislocation and cataract formation. The rare cataract can spontaneously improve in rare cases

Toxic Cataract
Toxic cataract has been reported in humans after local and systemic use of certain drugs, exposure to radiation and electric shock

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