At a Intraocular lens is an artificial lens that is inserted into the eye during a surgical procedure. The artificial lens remains permanently in the eye and significantly improves the patient's eyesight.
What is an intraocular lens?
Under intraocular lenses (IOL) are mostly understood to mean lens implants. The artificial lenses serve as a substitute for the natural lens of the eye. Replacing the human eye lens may be necessary in the context of a lens opacification such as a cataract. But even with very pronounced refractive visual defects, it is possible to use an intraocular lens in addition to the natural lens to correct the ametropia.
Intraocular lenses have been in use since 1949. That year, the British ophthalmologist Harold Ridley (1906-2001) installed the first artificial eye lens in London. In the years that followed, intraocular lens implantation became a widespread practice. In Germany alone, an average of 650,000 intraocular lenses are used in cataract operations each year.
Shapes, types & types
Intraocular lenses can be divided into different variants. The conventional intraocular lens is used as part of a cataract operation. Cataract is a clouding of the lens of the eye that leads to a deterioration in vision. Surgery to correct this problem has been tried and tested for decades and is performed around 14 million times a year worldwide. In the course of the procedure, the doctor replaces the clouded lens with the artificial lens, which enables the patient to see better immediately.
Another variant is the phakic intraocular lens. The insertion of the artificial eye lens is considered a safe alternative for people who are not suitable for laser eye therapy. It is used for severe nearsightedness, farsightedness or a thin cornea.
The ametropia is corrected by implanting the phakic intraocular lens in the eye, where it also remains next to the natural lens of the eye. The intervention can also be reversed at any time.
Intraocular lenses are divided into toric lenses, which correct nearsightedness, farsightedness and astigmatism, aspherical intraocular lenses, which are used to correct the "spherical aberration", presbyopia-correcting intraocular lenses that ensure sharp vision into the distance, and blue filter lenses. These have the function of stopping the transmission of blue light into the eye in order to protect the retina.
Another variant are the multifocal intraocular lenses, which guarantee sharp vision over several visual distances. In turn, they are divided into bifocal and trifocal intraocular lenses. While the bifocal lens, which is a classic of the multifocal intraocular lens, has two focal points, the trifocal lens has three focal points.
Structure & functionality
An intraocular lens consists of a central optical lens and a subsequent haptic, which ensures that the lens is fixed in the eye. The optical zone has a diameter of 5 to 7 millimeters. The feel has different shapes. Common variants are plate haptics or C haptics.
There are differences in the materials of the intraocular lens, which means that it can be divided into a foldable soft or a hard lens. While hard lenses are made of polymethyl methacrylate (PMMA), soft foldable intraocular lenses are made of hydrogel, acrylic or silicone.
The foldable lenses are provided with a smaller incision required for implantation. The foldable intraocular lenses can be inserted through an incision 3 millimeters in size. With modern lenses, even 2 millimeters are sufficient for implantation.
A phakic intraocular lens (PIOL) is composed of a central optical lens and a haptic on the periphery. The diameter of the optical zone is 4.5 to 6 millimeters. A distinction must be made between anterior and posterior chamber lenses. While the anterior chamber lens is implanted between the cornea and the iris, the posterior chamber lens is inserted between the eye lens and the iris.
The material of the Phakic intraocular lens is different. Anterior chamber lenses are made from soft materials such as acrylic or silicone compounds or hard PMMA. In contrast, posterior chamber lenses are always made of soft material such as collamer or silicone compounds.
The optical functions of the intraocular lens depend on the type of lens used. Positive refractive intraocular lenses, which are implanted in originally normal-vision eyes, are most commonly used. Negative refractive lenses correct extreme myopia and toric lenses are suitable for moderate to severe astigmatism. With a multifocal lens, the patient can do without reading glasses. Presbyopia can also be corrected.
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The intraocular lens is of great importance for ophthalmic medicine. It is an effective alternative to laser treatment and enables ametropia such as nearsightedness and farsightedness between -5 and +3 diopters to be corrected. A correction of astigmatism (corneal curvature) of up to 7 dioptres can also be achieved.
The corrective services vary depending on the type of lens. Even myopia of up to -20 dioptres or farsightedness up to +15 dioptres can be treated with a special intraocular lens.
To implant an intraocular lens, eye surgery is required. Compared to laser treatments, the result can be reversed. In addition, the lens exchange takes place on an outpatient basis. In addition, the operation has fewer risks. The intraocular lens is inserted into the eye through a small incision. The healing phase only takes about 24 hours and the patient quickly has better eyesight.
However, there are also some contraindications for the implantation of an intraocular lens. For example, the lens must not be used on people who have a chronic eye disease such as glaucoma. The same applies to patients under the age of 18.
