Disorders of the lens

Disorders of the lens are a group of relatively common diseases, especially of the cloudy type, where vision is impaired due to clouding of the lens or the formation of an obstruction. Some diseases are directly related to the lens, others may be related to other systemic diseases or problems in the body and may affect not only the lens directly but also the lens hinge apparatus. Since the lens helps focus the light beam onto the retina, it is an extremely important part of the eye.

The lens is a very important organ located behind the pupil and iris. Light rays pass through it to the retina, and due to its optical power and ability to change it, the lens is the most important for producing a sharp image in humans. Diseases of the lens are thus mainly concerned with the ability of the lens to transmit light rays from the external environment further into the eye to the retina, and if this ability is impaired, rapid or gradual deterioration of vision occurs.

The most common are various types of cataracts and opacities, when light is scattered in the lens and the person sees the objects in front of him as if through a screen or fogged. In the past, these opacities were quite a problem, but especially with the advent of modern laser technology in medicine, most of the opacities are now very easily removable and operable, even without a long convalescence. Several lens diseases also come with age.

Structure and function of the lens

The lens is a transparent formation and part of the eye deposited and the iris of the eye, while having a disc-shaped form. The lens is attached to the sclera, which is the part of the middle layer of the eyeball just behind the iris. This ciliary body allows changes in the curvature of the lens, or changes in focal length, by contractions of its muscles, one of the most important functions of the lens. This is because it can change its optical power and can bend the rays of light so that they converge on the retina.

This function is also called accommodation and allows for the creation of a sharp image in the eye. Over time as a person ages, however, the ability to form an image decreases, causing some types of age-related lens diseases. The lens is approximately 4 mm thick and has a curved back surface, with rays of light passing through it and the cornea towards the retina. The light enters through the cornea, from there it passes through an area filled with what is called the aqueous humor and strikes the lens and then the pupil.

When light rays pass through the lens, the lens, by means of its accommodation, is able to direct these rays to converge on the retina, where they form an inverted image, which the retina is able to process correctly and then send through the optic nerves to the brain. The lens is held in place by the fibres of the hinge apparatus, which is clamped between the processes of the so-called ciliary (ciliated) body, while the lens itself is elastic, enclosed in a sheath, and it is by the pull of the hinge apparatus that it can change its shape.

The ciliary body has projections in the anterior part which form a circle around the lens, and from it thin fibres extend to form the hinge apparatus of the lens. At the same time the muscle forming the total accommodative apparatus of the lens is embedded in this body. It makes the lens curve and change its refractive power, curving more when looking near, less when looking far or sometimes not at all. The lens is transparent, but with age the transparency decreases and the shape of the lens changes at the same time.

Age-related cataracts

As with other organs in the body or parts of the eye, the lens loses many of its important properties with increasing age and, in turn, is more susceptible to various defects and degeneration. This is also true in the case of clouding diseases, which are known professionally as cataracts. There are several types of cataracts affecting people as they advance in age, appearing mainly after the age of 60 and in similar proportions in both men and women, although women may be slightly more affected.

Cataract is an affection of the lens of the eye where chemical changes occur in the proteins that make up the lens, so that the transparent tissue begins to become opaque and cloudy, which from the outside looks like a whitening or greying of the lens; in some specific types of cataract, the lens may also be a different colour. The person loses visual acuity and looks at surrounding objects as if through a fog or a screen. Cataracts are also the most common lens problem and disease.

Senile cataracts include early stage senile cataracts, which may be coronal, crotic or punctate, also anterior and posterior subcapsular polar senile cataracts and early stage cataracts. Another type is the so-called phacoscleron, which is a cataract culcearis sclerotica. Senile cataracts also include senile cataract of Morgagni type, cataract senilis hypermatura and various combined types of senile cataract, including unspecified cataract.

Cataracts are one of the most common cataracts of the lens, and risk factors for cataracts include heredity, but also various infections or injuries to the eye or the use of certain types of medication, especially corticosteroids. In age-related cataracts, there is a gradual loss of transparency, i.e. vision deteriorates. Senile cataract has four basic forms namely nuclear, cortical, posterior subcapsular and a form of mature cataract.

In the nuclear form, it is a secondary type, which occurs relatively quickly, yellowing of the lens and the formation of central opacity. Sometimes the opacity may also be brown in colour. In the cortical form, there are ionic changes in the composition of the lens cortex and excessive stress on some fibres. In the subcapsular form of opacity, a granular coating appears in the posterior cortex of the lens causing blurred vision. The most severe form is mature opacity affecting the entire lens, which is completely opaque.

Cataracts related to other diseases

In addition to age-related forms of cataracts, there are also so-called secondary cataracts, which are cataracts resulting from other diseases, such as various metabolic disorders and the like. Very common is cataract resulting from diabetes, also called cataracta diabetica. In addition, inflammation also arises in other endocrine, nutritional and metabolic diseases, such as cataracts in hypoparathyroidism or malnutritional-dehydrating cataracts.

Cataracts that are related to other diseases in the body include myotonic cataracts. This is a cataract that can also be a symptom for myotonic dystrophy, which is a multisystem disorder affecting multiple systems in the body, namely the skeletal muscles, smooth muscles, eyes, heart, endocrine system and of course the central nervous system. It is in the mild form of myotonic dystrophy that the development of opacities occurs in conjunction with mild myotonia.

Very often cataracts are also associated with diabetes, sometimes in combination with diabetic retinopathy. It is also called diabetic cataract, and in this cataract both spatial vision and the colour and brightness of the image are impaired. In people with diabetes, cataracts occur much more frequently and more quickly than in the general healthy population, so people with diabetes, for example, should have more frequent ophthalmic lens examinations by a specialist.

Also, atopy or galactosemia is more likely to cause cataracts. In addition, some other infectious diseases, such as rubella, also affect the eye and cause cataract, or Gregg's syndrome, and sometimes toxoplasmosis or iritis, especially secondary anterior iritis in the chronic form, or inflammation in the central part of the iris.

Traumatic, drug-induced and other cataracts

Cataracts, or cataracts, are also caused by traumatic changes when the eye is injured. Also, secondary cataracts or Soemmerring's ring can form after cataract extraction. Secondary cataract itself is caused by deterioration of visual acuity due to thickening or graying of the posterior lens capsule after primary cataract surgery and is thus a consequence of this procedure. The treatment is laser surgery via laser capsulotomy.

Cataracts can also form after taking certain medications, such as corticosteroids. Other types of cataracts include infantile, juvenile and presenile cataracts, complicated cataracts, for example in chronic iridocyclitis or as a result of other eye diseases. Sometimes cataract formation also occurs after surgery to correct retinal detachment. Congenital cataracts, most often inherited from the mother during prenatal development, are very problematic.

Cataracts as such are manifested by blurred and reduced vision and reduced visual acuity and are most often treated by laser removal of the cloudy lens and replacement with a new, artificial lens. The original clouded lens is removed from the clear original lens case and a new lens is implanted, which is individually designed for each patient. The operations are only performed when the eye in question is locally numb.

Dislocations, aphakias and other diseases

Examples of other lens problems include changes to their original position within the eye, or complete or partial absence of the lens. The lens is also affected by congenital defects, mechanical disorders and complications of the intraocular part of the lens, pseudophakia, aphakia of the lens, lens dislocation or presbyopia, which is the loss of the accommodative ability of the lens due to old age. Accommodative ability means the focusing of the lens and the ability to change the optical power.

Dislocation of the lens is also common, which can be congenital or acquired due to the formation of a secondary glaucoma, i.e. glaucoma. This is a partial displacement of the location of the lens, which causes problems in focusing light rays to the back of the eye onto the retina. Severe cases even lead to complete loss of the eye's ability to focus objects, and sometimes even surgery won't help. However, milder cases can be corrected, most often by laser coagulation.

The complete absence of the lens in the eye is called aphakia and it is the destruction of the lens most often by a pathological process such as inflammation or injury to the eye. Since the complete loss of the lens means a significant change for the eye in terms of the optical system, the eye becomes significantly hyperopic, i.e. the light rays are not refracted by the lens onto the retina but are projected beyond it. However, this condition can be compensated for either by glasses or by direct surgical implantation of an artificial lens.