An intraocular lens is an artificial lens that is inserted into the eye during a surgical procedure. The artificial lens remains in the eye permanently and significantly improves the patient’s vision.
What is an intraocular lens?
An intraocular lens is an artificial lens that is inserted into the eye during a surgical procedure. Intraocular lenses (IOLs) most commonly refer to lens implants. The artificial lenses serve as a replacement for the natural lens of the eye. Replacing the human eye lens may be necessary in the context of lens opacification such as cataract. However, it is also possible to insert an intraocular lens in addition to the natural lens to correct refractive errors in cases of severe refractive errors. Intraocular lenses have been in use since 1949. In that year, the British ophthalmologist Harold Ridley (1906-2001) implanted the first artificial eye lens in London. In the following years, the implantation of intraocular lenses developed into a widespread procedure. In Germany alone, an average of 650,000 intraocular lenses are implanted each year during cataract surgery.
Forms, types, and styles
Intraocular lenses can be divided into different varieties. The conventional intraocular lens is used as part of cataract surgery. Cataract is the term used to describe a clouding of the lens of the eye that causes vision to deteriorate. Surgery to correct this problem has been around for decades and is performed about 14 million times a year worldwide. During the procedure, the doctor replaces the clouded lens with the artificial lens, which immediately provides the patient with better vision. 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 in cases of severe nearsightedness, farsightedness or thin cornea. The correction of refractive error is performed by implanting the phakic intraocular lens into the eye, where it additionally remains next to the natural lens of the eye. In addition, the procedure can be reversed at any time. Intraocular lenses are divided into toric lenses, which correct nearsightedness, farsightedness and astigmatism, aspheric intraocular lenses, which correct the aberration “spherical aberration”, age-related intraocular lenses, which ensure sharp vision in the distance, and blue filter lenses. These have the function of stopping the transmission of blue light into the eye to protect the retina. Another variant is multifocal intraocular lenses, which ensure sharp vision over multiple visual distances. They are again divided into bifocal and trifocal intraocular lenses. While the bifocal lens, considered the classic of multifocal intraocular lenses, has two focal points, the trifocal lens has three focal points.
Structure and mode of operation
An intraocular lens is composed of a central optical lens and a subsequent haptic zone that provides fixation of the lens in the eye. The optical zone has a diameter of 5 to 7 millimeters. The haptic has different shapes. Common variants are plate haptics or C-haptics. Differences exist in the materials of the intraocular lens, which allows it to be divided into a foldable soft lens or a hard lens. While hard lenses are composed of polymethyl methaacrylate (PMMA), soft foldable intraocular lenses are made of hydrogel, acrylic or silicone. Foldable lenses are designed with a smaller incision required for implantation. For example, foldable intraocular lenses can be implanted through an incision 3 millimeters in size. With modern lenses, even 2 millimeters is sufficient for implantation. A phakic intraocular lens (PIOL) is composed of a central optical lens and a haptic at the periphery. The diameter of the optical zone is 4.5 to 6 millimeters. A distinction must be made between anterior chamber and posterior chamber lenses. While the anterior chamber lens is implanted between the cornea and the iris, the posterior chamber lens is implanted between the crystalline lens and the iris. The material of the phakic intraocular lens varies.For example, anterior chamber lenses are composed of soft materials such as acrylic or silicone compounds or hard PMMA. In contrast, posterior chamber lenses are always made of soft materials such as collamer or silicone compounds. The optical functions of the intraocular lens depend on the type of lens. The most commonly used intraocular lenses are positive refractive lenses, which are implanted in eyes that originally had normal vision. Negative refractive lenses correct extreme nearsightedness and toric lenses are suitable for moderate to severe astigmatism. A multifocal lens allows the patient to eliminate the need for reading glasses. In addition, presbyopia can be corrected.
Medical and health benefits
For ophthalmology, the intraocular lens is of great importance. For example, it is an effective alternative to laser treatment and allows correction of refractive errors such as nearsightedness and farsightedness between -5 and +3 diopters. Likewise, correction of astigmatism (astigmatism of the cornea) of up to 7 diopters can be achieved. The corrective performance varies depending on the type of lens. Even nearsightedness of up to -20 diopters or farsightedness of up to +15 diopters can be treated with a special intraocular lens. In order to implant an intraocular lens, an ophthalmic surgical procedure is required. Compared to laser treatments, the result can be reversed. In addition, lens replacement is performed on an outpatient basis. In addition, the surgery has fewer risks. For example, the intraocular lens is inserted into the eye through a small incision. The healing phase lasts only about 24 hours and the patient’s vision improves quickly. However, there are some contraindications to the implantation of an intraocular lens. For example, the lens must not be implanted in people who have a chronic eye disease such as glaucoma. The same applies to patients under 18 years of age.
