The crystalline lens is located in the eye directly behind the pupil. It is transparent and has a curvature that refracts incoming light and then projects it onto the retina. This enables sharp vision. Due to the elasticity of the crystalline lens, the curvature adapts. This enables sharp vision at different distances. Diseases of the lens of the eye are cataracts and lens ectopia.
Below you will find further information such as selected specialists for diseases of the lens of the eye.
The elastic lens of the eye is approx. 4 mm thick with a diameter of 9 to 10 mm at rest and is located directly behind the pupil, between the vitreous body and the iris. It consists of long, thin lens fibers. The lens nucleus is located in the center. It is surrounded by the lens cortex.
The structure of the human eye
The light that hits the eye is refracted in the lens and projects a more or less sharp image onto the inner skin of the eye. The optic nerve transmits the impulses to the brain.
The change in the curvature of the crystalline lens therefore determines the near and far vision of the eye. The aim of lens adaptation is to project the image as sharply as possible onto the retina.
How a lens works: Refraction of light and projection onto a specific point
Near accommodation
The ciliary muscle (ciliary muscle) is located on the outside of the ciliary body. When changing from distance to near vision (near accommodation), the elastic zonular fibers that connect the lens of the eye to the body of the ray relax. The lens curves into a spherical shape due to its high elasticity. It refracts the incident light to project a sharp image onto the retina.
Distance accommodation
When switching from near to far vision (distance accommodation), the ciliary muscle relaxes and the zonular fibers tighten. The eye lens flattens as a result of the tension. Due to the reduced curvature, the incident light from the body (at a greater distance) is refracted more weakly. The sharp image on the retina is created by the flattening.
The intensity with which the lens of the eye refracts the light passing through it is indicated by the unit of measurement diopter (dpt).
This ability of the lens to adapt to near and distance vision begins to decline in adolescence. The core of the lens hardens in the course of life and the lens loses its elasticity (presbyopia).
Presbyopiais not a disease. The loss of function of the lens of the eye makes it increasingly difficult to see close objects clearly. Reading glasses correct presbyopia.
During the slow, progressive deterioration of vision over the years, the affected person perceives a veil of fog in front of their eyes. Those affected can recognize light and dark as well as the direction of the incident light.
Vision of a healthy eye (left), next to it vision of an eye suffering from cataracts
Twilight causes fewer problems for the lens than daylight, as the pupil dilates in poor light conditions and can therefore "see past" the clouding of the lens.
Sunlight and other strong light sources, on the other hand, refract diffusely in the cloudy lens of the eye and cause glare. Sunglasses or avoiding bright light are therefore advisable for affected people
There are different types of cataract depending on the location of the opacity:
In a nuclear cataract (cataracta nuclearis), the nucleus of the lens becomes cloudy. The center of the lens of the eye swells. The resulting short-sightedness can mean that people with presbyopia can read again without glasses.
In cortical cataracts (cataracta corticalis), the clouded part of the crystalline lens is located in the anterior or posterior cortex of the lens. Fissures and spokes are formed in the lens cortex. Double vision occurs in front of the affected eye.
If the central opacity is located in the posterior cortex of the crystalline lens directly in front of the posterior capsule, there is a deterioration in vision with little lens opacity. This rapidly progressing posterior clouding of the crystalline lens (cataracta subcapsularis posterior) causes the most severe glare.
Congenital cataracts in both eyes (congenital cataracts) are usually caused by the parents' genes. An infectious disease of the mother during pregnancy (mumps or rubella) can also be the cause.
Depending on the type and extent of the opacity, a distinction is made between capsular, polar, central, layered or point cataracts.
In contrast to congenital cataracts, cataracts acquired in the course of life usually only affect one eye.
Cataracts in the eye
At 90 %, senile cataract (cataracta senilis) is the most common form. As a result of the natural ageing process, metabolic processes in the lens of the eye cannot be maintained. This form of cataract is not only promoted by enzyme changes and nutritional disorders, but also by ultraviolet light.
The progression of age-related cataracts is divided into different stages:
In the early stage, with incipient cataracts (cataracta incipiens), the affected person notices a barely disturbing clouding of the lens of the eye.
The increased clouding of the lens of the eye occurs in immature cataracts (cataracta provecta) and already impairs vision with the clouded eye.
The clouding of the lens of the eye in the mature cataract stage (cataracta matura) is so advanced that the patient can only see light and shadow.
A further complication is the swelling of the lens of the affected person's eye. The displacement of the iris can trigger an acute increase in eye pressure (glaucoma attack) in the eye, as with glaucoma.
In the final clouding stage, the cortex of the crystalline lens liquefies and the hard lens nucleus sinks downwards.
The displacement of the lens of the eye (also known as lens ectopia) can result in glaucoma , which destroys the nerve fibers of the eye.
The clouding of the lens of the eye due to an injury is also an acquired cataract.
They have different names depending on the cause:
Diseases can also be the cause of cataracts: Diabetes mellitus, metabolic disorders and various kidney, skin and muscle diseases have a negative effect on vision and cause cataracts as a concomitant disease.
Although the clouding of the lens of the eye can be halted by treatment, it cannot be reversed.
The lens of the eye can also become cloudy following eye surgery or other eye diseases: For example, after inflammation of the iris or prolonged use of medication such as cortisone.
Although an advanced cataract can be detected without technical equipment, the clouding of the lens of the eye is diagnosed with a slit lamp examination when the pupil is dilated.
Slit lamp examination
Cataracts cannot be treatedwith medication, which is why cataract surgery is necessary to restore vision. This involves replacing the cloudy lens of the eye with a new artificial lens.
The most common surgical procedures are
During intracapsular lens extraction, the body's own lens is removed from the eye. Intracapsular lens extraction is often used in cases of chronic inflammation. A serious late consequence of this procedure is a possible retinal detachment.
Extracapsular lens extraction is used most frequently. In this procedure, the posterior lens capsule remains in the eye. The surgeon only removes the anterior lens capsule and the cloudy material of the crystalline lens.
Sometimes the lens of the eye becomes cloudy again after the operation. This is due to remaining capsule residue, which causes the pupil opening to close again. This secondary cataract is treated using laser therapy.
The inserted artificial lens is not elastic like the natural lens. It is therefore unable to adapt to the curvature. The lack of refractive power is compensated for with contact lenses or glasses.
During the follow-up treatment, the patient is given eye drops containing antibiotics and corticoids to prevent inflammation and infection.
In lens ectopia, the lens shifts into the anterior chamber of the eye or into the vitreous cavity.
In most cases, the irregular change in position of the lens of only one eye is acquired as a result of an injury, for example.
Bilateral lens ectopia, i.e. changes in the position of the lenses of both eyes, is usually associated with malformations or a genetic predisposition.
There are various forms of lens ectopia:
In lens luxation (luxatio lentis), the lens of the eye is completely displaced due to the tearing of the lens attachment. The torn lens is therefore located at the bottom of the vitreous body, more rarely in the anterior chamber of the eye.
The displacement of the lens into the vitreous body and the breakdown of lens fibers often leads to inflammation. As only the cornea is responsible for refraction in the absence of the lens, this results in hyperopia.
In subluxation (subluxatio lentis), the lens of the eye partially dislocates from the pupil due to loosening of the zonular fibers. The lens, which is usually reduced in size (microphakia), takes on a spherical shape (spherophakia). The excessive refractive power of the spherical lens results in short-sightedness (myopia).
In the case of iridodonesis, the suspension is weakened. This results in abnormal mobility of the crystalline lens in the eye.
Slight lens dislocations can remain symptom-free. If the displacement of the crystalline lens is more severe, double vision may be perceived. The vision of the eyes deteriorates significantly due to the reduction in the refractive power. Short-sightedness is the result.
The causes of lens ectopia vary:
The unfixed lens can cause damage to the cornea, which in turn can lead to corneal opacity. The displaced crystalline lens is surgically removed (lensectomy). Instead, the patient receives an artificial lens.
A rare disease of the crystalline lens is the formation of a slit in the eye. This can be congenital or caused by injuries and operations on the eye. Depending on its size and severity, the cleft affects the patient's vision.
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