• Decoding of online tests - urine, blood, general and biochemical.
  • What do bacteria and inclusions in urine analysis mean?
  • How to understand the analysis of the child?
  • Features of MRI-analysis
  • Special tests, ECG and ultrasound
  • Pregnancy rates and variance values ​​..
Explanation of analyzes

Intraocular lenses: a modern way to improve vision

Diseases of the eyes in modern society are extremely common. More than half of the world's population has poor eyesight. Myopia, hyperopia, astigmatism, clouding of the lens - all these shortcomings modern medical science has learned to treat by implantation in the eyeball intraocular lenses.

Content

Optical system of the eye

The eye is a unique creation of nature. The organ of vision is capable of converting light information into an electrical nerve impulse with the help of several anatomical structures. The eyeball is a thin optical system. The image of the object is formed in an inverted form on the retina located on the fundus. However, it receives a beam of light, undergoing focusing in optical media.

The structure of the optical system of the eye

The optical system of the eye is a complex anatomical structure

The first refractive structure of the eye is the cornea. It has an almost spherical shape and the greatest optical power is 26-28 diopters. A transparent cornea directs the light beam into the anterior chamber of the eye. It is the space between the cornea and the iris, filled with special moisture. Behind the aperture of the pupil is the posterior chamber of the eye, also containing a liquid. Optical force of moisture is low.

The second main refractive structure of the eye is the lens. This organ consists of tissue, from birth, separated from the body's immune system, therefore it has no vessels. The lens is surrounded on all sides by the fibers of the ciliary muscle. They are able to change its shape and curvature, which makes it possible to clearly distinguish objects located at the near and far distances. Optical power of the lens is about 18-19 diopters.

The structure of the anterior part of the eyeball

Lens - the basic structure providing clear vision in the distance and near

Following the lens there is a vitreous body, behind which there is a photosensitive envelope of the eye - the retina. Passing all the optical structures, a ray of light falls on a yellow spot - a large accumulation of specific cells: rods and cones. With their help, the image of the object is formed. The whole image of the surrounding world is a product of the functioning of the brain.

The principle of the intraocular lenses

Intraocular lenses are invented by man for correction of the optical system. The causes of decreased visual acuity:

  • myopia;
  • farsightedness;
  • astigmatism;
  • cataract.

With myopia due to an increase in the length of the eyeball, the image of the object is formed not in the retina, but in front of it. Hyperopia is observed when the eyeball is shortened. In this case, the image of the object is formed behind the retina. The placement in the eyeball of an artificial additional lens of the appropriate force makes it possible to obtain a qualitative image of the surrounding world.

Scheme of formation of myopia and hyperopia

Myopia and hyperopia are indications for implantation of intraocular lenses

Astigmatism is a phenomenon associated with the different curvature of individual sections of the cornea. A light beam that has passed through such an optical system falls on the retina at several points. In this case, a clear image of the object does not work. Adding an additional lens to the eyeball with a certain curvature at different sites allows you to compensate for this condition.

Diagram of the formation of astigmatism

Astigmatism is amenable to correction with the help of toric intraocular lenses

Cataract is a term for clouding the lens. Light lingers in it and does not get on the retina. In this case, correct vision will help remove the cloudy lens surgically and place the intraocular lens in its place.

Video: age-long farsightedness and methods of its correction

Types of intraocular lenses

Manufacturers offer a variety of models of intraocular lenses designed to treat various diseases. Intraocular implants are divided into several groups:

  1. By type of vision correction:
    • Afakichnaya lens - used to correct vision after removal of the lens for cataracts. In this case, the implant is placed in place of the lost optical structure. By the imaging method, these lenses are divided into several types:
      • monofocal, allowing you to see clearly only close or remote objects;
        The scheme of action of a monofocal lens

        Monofocal lens focuses a beam of light on the retina

      • multifocal, allowing you to clearly distinguish objects in the near and far distances;
      • Encoders, capable of changing their curvature under the influence of ciliary muscle fibers of the eye;
      • Toric, having a different curvature and serving to eliminate the phenomena of astigmatism;
    • Phakic lens - used in the case of myopia, hyperopia and astigmatism. In doing so, it serves as an additional optical structure while preserving its own, including the lens.
  2. By the method of installation intraocular lenses are divided into two types:
    • anterior chamber - in this case the lens is located between the cornea and the pupil opening;
    • posterior chamber - the implant is located behind the lens.
      The mechanism of action of the posterior chamber lens

      The lens collects a beam of light at a point on the retina of the eye

  3. By type of material intraocular lenses are divided into:
    • Flexible, made of silicone or polymers;
    • Hard, made of plastic.

Photogallery: models of intraocular lenses

Intraocular lenses should meet the following requirements:

  • installation in the eyeball through a minimal cut of the cornea;
  • maintaining a stable position within the eye;
  • no risk of clouding of the lens (secondary cataract);
  • protection of the retina from harmful ultraviolet radiation.

All intraocular lenses consist of two main parts:

  • optical, which corrects the image;
  • haptic, which serves to hold the lens in the eyeball in the required position (for this purpose, the design provides for the presence of unique legs that ensure the fixation of the implant in the desired position).

Video: selection of intraocular lenses

Features of different types of intraocular lenses

The choice and installation of different types of intraocular lenses is done by a doctor to solve specific problems. Each model has its advantages and disadvantages of implantation and subsequent use.

Phakic lenses

Phakic lenses the doctor suggests to establish those people who suffer from a decrease in visual acuity due to myopia, hyperopia or astigmatism. The reasons for rejecting the usual methods of correction with the help of glasses, contact lenses and laser surgery can be several:

  • high degree of visual acuity reduction;
  • diseases of the cornea (keratoconus, keratoglobus), in which laser vision correction is contraindicated;
    Keratoconus

    Visual acuity in keratoconus can not be corrected by laser correction

  • thin cornea, the residual thickness of which after the laser correction is not enough for the normal functioning of the eye.

Intraokuljarnye lenses allow to correct a sharpness of vision in wide limits from-25 to +20 diopters.

Phakic lenses can be installed both before and behind their own lens. However, the first method is used less often due to the frequent development of high intraocular pressure after surgery. In addition, this kind of lens can not correct astigmatism. After installing such an implant, the patient will be forced to wear glasses to correct visual acuity. Zadnokamernye implants are currently used more often. In this position, you can establish a toric lens that corrects astigmatism.

Implantation scheme for the anterior chamber and posterior chamber lenses

Zadnekamernaya position is currently the most popular

Phakic lenses are not installed in patients in the following cases:

  • the presence of clouding of the lens (cataracts);
  • instability of the lens position (subluxation);
  • Initially high intraocular pressure (glaucoma);
  • diseases of the retina and vitreous humor, in which even with the intraocular lens it is impossible to get a clear image of the subject;
  • surgical treatment in the past of glaucoma, retinal and vitreous diseases;
  • the depth of the anterior chamber of the eye is less than 3 millimeters;
  • the depth of the posterior chamber of the eye is less than 2.5 millimeters.

In all these cases, the patient will have to use glasses, contact lenses or laser intervention to correct for the presence of visual impairments.

Installation of phakic lenses

The installation of a phakic lens in the eyeball does not require hospitalization and general anesthesia (anesthesia). This procedure is performed by an ophthalmologist on an outpatient basis. Special preparation is not required before implantation. Before the procedure for installing the posterior chamber lenses, the pupil is dilated with the help of medications (Atropine). Before the beginning of the operation, local anesthesia is carried out with an anesthetic in the form of drops.

As an access to the anterior or posterior chamber of the eye, an incision of a cornea of ​​no more than 2 millimeters in length is used, which upon completion will independently create a tightness of the cavities of the eyeball and prevent it from penetrating into the infection. A flexible lens with a special tool is straightened out and positioned in the desired position.

Intraocular lens installation

The installation of the intraocular lens is carried out on an outpatient basis through a tiny incision in the cornea

When a toric lens is implanted, it must be properly installed. To do this, the cornea of ​​the eye is marked with a special marker. The areas of the modified curvature of the lens are combined with them, thereby correcting astigmatism. After the operation, the doctor will not impose seams. The whole procedure takes no more than ten to twenty minutes.

Schematic of the installation of a toric lens

The success of correcting astigmatism with the intraocular lens depends on the correctness of its installation

Features of aphakic lenses

Afakichnye lenses are used after the removal of their own lens for cataracts. As a result of the intervention, changes occur in the optical system of the eye, leading to a strong farsightedness of 12-14 diopters. The implantation of an aphakic lens solves this problem. However, not all models have only merit.

Vision is normal and with cataract

When the lens becomes clouded, the light does not reach the retina

Monofocal lenses after installing the remote lens in place, depending on the optical power will allow you to clearly see objects located only near or at a long distance. The latter type is implanted to drivers and pilots who are vitally needed for their professional duties to have clear vision in the distance. In this case for reading these patients will have to use plus glasses. If there is an initial astigmatism, the doctor prescribes a point correction to eliminate this phenomenon.

Scheme of installation of aphakic lenses

Apakichnaya lens is often installed in the rear-chamber position

Multifocal lenses allow you to clearly distinguish objects located at different distances. However, the cost of such implants is much higher. The effect of clear vision is achieved by varying the curvature of individual sections of the lens.

Toric lenses are able to correct astigmatism no more than 6 diopters, which was before surgery and associated with a change in the curvature of the cornea. These implants belong to the premium class, their cost is high. The accommodation lenses are designed to help a person to see clearly objects located at different distances after the removal of the lens. This lens can change the curvature under the influence of the ciliary muscle. This kind of implants also belongs to the premium class.

The scheme of the structure of a multifocal lens

Multifocal lens due to the presence of zones with different optical power allows you to clearly see objects near and far

Installation of aphakic lenses

Before installing the aphakic lens, surgical removal of the lens tissue is necessary. This procedure can be performed by a doctor both in outpatient and hospital settings. Before the operation, local anesthesia with anesthetic drops is performed.

As an access, a corneal incision is used. Through it and the opening of the pupil to the lens is a special instrument. After this, the cataract phacoemulsification procedure begins. The destruction of the lens tissue is carried out by means of ultrasound. Intraocular lens is installed on the site of the removed structure. More often for this, a posterior chamber position is used, less often anterior chamber.

Scheme of operation for cataracts

When cataracts are removed, the lens is implanted with the intraocular lens

After installing the aphakic lens, visual defects due to calculation errors may remain. Removing the implant is a complicated procedure. In this case, the installation of an additional pseudo-fake lens is used.

Complications of intraocular lens implantation

A simple, at first glance, procedure for installing a lens through a tiny cut of the cornea can in some cases lead to serious consequences:

  • Endophthalmitis. Through the incision into the eyeball can penetrate the infection and cause a purulent inflammation of all parts. Treatment of this process is very difficult. Such a pathology can lead to irreversible blindness.
  • Pupillary block. When the phakic lens is located in the posterior chamber, outflow of moisture through the pupil opening may be disturbed. Usually this problem is solved before or during the operation by forming several holes in the iris to ensure a normal circulation of fluid in the eye.
  • Pupil ovulation. Incorrect determination of the size and position of the phakic lens in the anterior chamber of the eye can cause a change in the shape of the pupil and the appearance of glare.
  • Increased intraocular pressure. The moisture from the cavities of the eye flows into the structures of the angle of the anterior chamber. The fixing elements of the lens can exert pressure on it, which leads to a disruption of the normal circulation of fluid within the eye.
    Eye with a lens installed in the anterior chamber

    When installed in the anterior lens chamber, glaucoma may develop

  • The development of cataracts. With the implantation of phakic lenses, they can contact their own lens, which causes its turbidity.
    Opacid lens of the eye

    After the installation of the phakic lens, clouding of the lens may develop

  • Displacement of the implant. This complication can occur with the installation of any type of intraocular lens. In the case of accommodating models, this process is additionally accompanied by rupture of the fibers of the ciliary muscle.

It must be remembered that the installation of the intraocular lens, despite its seeming simplicity, is not completely reversible. The eyeball after the implant removal procedure will never be the same again. The risk of his purulent inflammation (endophthalmitis) is significantly increased after the procedure. In addition, the re-operation is technically more difficult than the primary operation and can be accompanied by irreversible changes. If inflammation occurs in the ciliary body, the retina is also subject to removal.

Laser vision correction

In some cases, it is more preferable to perform a laser vision correction

Intraocular lenses are a significant achievement of modern ophthalmology. However, the choice of the method of vision correction is always left for the doctor. Only a specialist is able to adequately assess the degree of visual disturbances and prevent the development of complications.

Interesting

The information is provided for information and reference purposes, a professional physician should prescribe a diagnosis and prescribe a treatment. Do not self-medicate. | | Contact Us | Advertising | © 2018 Medic-Attention.com - Health On-Line
Copying of materials is prohibited. Editorial site - info @ medic-attention.com