Multifocal intraocular lens

Last updated August 24, 2024

Multifocal and accommodating intraocular lenses are artificial intraocular lenses (IOLs) that are designed to provide focus of both distance and near objects, in contrast to monofocal intraocular lenses which only have one focal point and correct distance vision. The issue of restoring accommodation following cataract surgery or through refractive lens exchange is becoming an increasingly important topic in ophthalmology.

Intraocular lenses that correct presbyopia are divided into two main categories:^[1]

Multifocal IOLs: achieve near and distance vision by having two (bifocal) or three (trifocal) focal points simultaneously. The function of multifocal IOL depends on the pupil size for refractive types. The concept is based on the principle that the pupil tends to constrict for near tasks, so the central portion of the lens is designed for near and the outer portion for distance. For diffractive types of multifocal IOLs, light is split by diffraction and the vision is pupil independent. However, the physics behind a diffractive IOL appears different from the well-known diffraction at the edges or corners of an obstacle. The property of a diffractive IOL in focusing light is explained by Snell's law of refraction on micro prisms ordered in concentric rings. The interference of diffracted light at the edges may reduce the quality of the image, but it does not play a role in the image formation of a diffractive IOL. Therefore, the term "diffractive" could be misleading in this context.
Accommodating IOLs: change in shape and power when the ciliary muscle contracts and give an advantage over regular IOLs.

Evidence about different lenses

Monofocal lenses are standard lenses used in cataract surgery. People who have a multifocal intraocular lens after their cataract is removed may be less likely to need additional glasses compared with people who have standard monofocal lenses.^[2] People receiving multifocal lenses may experience more visual problems, such as glare or haloes (rings around lights), than with monofocal lenses.^[2]

People receiving accommodative intraocular lenses had improvements in near vision but these improvements were small and reduced over time.^[3] People who received accommodative intraocular lenses may have a higher risk of thickening and clouding of the tissue behind the intraocular lenses (posterior capsule opacification) but there is some uncertainty around this finding.^[3]

Related Research Articles

Far-sightedness, also known as long-sightedness, hypermetropia, and hyperopia, is a condition of the eye where distant objects are seen clearly but near objects appear blurred. This blur is due to incoming light being focused behind, instead of on, the retina due to insufficient accommodation by the lens. Minor hypermetropia in young patients is usually corrected by their accommodation, without any defects in vision. But, due to this accommodative effort for distant vision, people may complain of eye strain during prolonged reading. If the hypermetropia is high, there will be defective vision for both distance and near. People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus. Newborns are almost invariably hypermetropic, but it gradually decreases as the newborn gets older.

Presbyopia is physiological insufficiency of accommodation associated with the aging of the eye that results in progressively worsening ability to focus clearly on close objects. Also known as age-related farsightedness, it affects many adults over the age of 40. A common sign of presbyopia is difficulty reading small print which results in having to hold reading material farther away. Other symptoms associated can be headaches and eyestrain. Different people will have different degrees of problems. Other types of refractive errors may exist at the same time as presbyopia. This condition is similar to hypermetropia or far-sightedness which starts in childhood and exhibits similar symptoms of blur in the vision for close objects.

$Radial keratotomy Refractive surgical procedure to correct myopia (nearsightedness$

Radial keratotomy (RK) is a refractive surgical procedure to correct myopia (nearsightedness). It was developed in 1974 by Svyatoslav Fyodorov, a Russian ophthalmologist. It has been largely supplanted by newer, more accurate operations, such as photorefractive keratectomy, LASIK, Epi-LASIK and the phakic intraocular lens.

Phacoemulsification is a cataract surgery method in which the internal lens of the eye which has developed a cataract is emulsified with the tip of an ultrasonic handpiece and aspirated from the eye. Aspirated fluids are replaced with irrigation of balanced salt solution to maintain the volume of the anterior chamber during the procedure. This procedure minimises the incision size and reduces the recovery time and risk of surgery induced astigmatism.

An Intraocular lens (IOL) is a lens implanted in the eye usually as part of a treatment for cataracts or for correcting other vision problems such as short sightedness and long sightedness; a form of refractive surgery. If the natural lens is left in the eye, the IOL is known as phakic, otherwise it is a pseudophakic lens. Both kinds of IOLs are designed to provide the same light-focusing function as the natural crystalline lens. This can be an alternative to LASIK, but LASIK is not an alternative to an IOL for treatment of cataracts.

$Refractive error Problem with focusing light accurately on the retina due to the shape of the eye$

Refractive error is a problem with focusing light accurately on the retina due to the shape of the eye and/or cornea. The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. Near-sightedness results in far away objects being blurry, far-sightedness and presbyopia result in close objects being blurry, and astigmatism causes objects to appear stretched out or blurry. Other symptoms may include double vision, headaches, and eye strain.

<span class="mw-page-title-main">Phakic intraocular lens</span> Lens implanted in eye in addition to the natural lens

A phakic intraocular lens (PIOL) is an intraocular lens that is implanted surgically into the eye to correct refractive errors without removing the natural lens. Intraocular lenses that are implanted into eyes after the eye's natural lens has been removed during cataract surgery are known as pseudophakic.

Cataract surgery, also called lens replacement surgery, is the removal of the natural lens of the eye that has developed a cataract, an opaque or cloudy area. The eye's natural lens is usually replaced with an artificial intraocular lens (IOL) implant.

Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at night. Astigmatism often occurs at birth and can change or develop later in life. If it occurs in early life and is left untreated, it may result in amblyopia.

Trabeculectomy is a surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye's trabecular meshwork and adjacent structures. It is the most common glaucoma surgery performed and allows drainage of aqueous humor from within the eye to underneath the conjunctiva where it is absorbed. This outpatient procedure was most commonly performed under monitored anesthesia care using a retrobulbar block or peribulbar block or a combination of topical and subtenon anesthesia. Due to the higher risks associated with bulbar blocks, topical analgesia with mild sedation is becoming more common. Rarely general anesthesia will be used, in patients with an inability to cooperate during surgery.

Vision of humans and other organisms depends on several organs such as the lens of the eye, and any vision correcting devices, which use optics to focus the image.

Laser blended vision is a laser eye treatment which is used to treat presbyopia or other age-related eye conditions. It can be used to help people that simply need reading glasses, and also those who have started to need bifocal or varifocal spectacle correction due to ageing changes in the eye. It can be used for people who are also short-sighted (myopia) or long-sighted (hyperopia) and who also may have astigmatism.

The eye, like any other optical system, suffers from a number of specific optical aberrations. The optical quality of the eye is limited by optical aberrations, diffraction and scatter. Correction of spherocylindrical refractive errors has been possible for nearly two centuries following Airy's development of methods to measure and correct ocular astigmatism. It has only recently become possible to measure the aberrations of the eye and with the advent of refractive surgery it might be possible to correct certain types of irregular astigmatism.

$Multifocal diffractive lens$

A multifocal diffractive lens is a diffractive optical element (DOE) that allows a single incident beam to be focused simultaneously at several positions along the propagation axis.

In ophthalmology, glued intraocular lens or glued IOL is a surgical technique for implantation, with the use of biological glue, of a posterior chamber IOL in eyes with deficient or absent posterior capsules. A quick-acting surgical fibrin sealant derived from human blood plasma, with both hemostatic and adhesive properties, is used.

Intraocular lens scaffold, or IOL scaffold technique, is a surgical procedure in ophthalmology. In cases where the posterior lens capsule is ruptured and the cataract is present, an intraocular lens (IOL) can be inserted under the cataract. The IOL acts as a scaffold, and prevents the cataract pieces from falling to the back of the eye. The cataract can then be safely removed by emulsifying it with ultrasound and aspiration. This technique is called IOL scaffold, and was initiated by Amar Agarwal at Dr. Agarwal's Eye Hospital in Chennai, India.

Cochrane Eyes and Vision (CEV) is a collaboration of researchers and healthcare professionals who prepare systematic reviews to study interventions pertaining to the treatment of eye disease and visual impairment. Though many of the systematic reviews focus on common eye diseases, reviews have been prepared for varied eye topics, including screening prevention and rarer eye diseases.

Secondary glaucoma is a collection of progressive optic nerve disorders associated with a rise in intraocular pressure (IOP) which results in the loss of vision. In clinical settings, it is defined as the occurrence of IOP above 21 mmHg requiring the prescription of IOP-managing drugs. It can be broadly divided into two subtypes: secondary open-angle glaucoma and secondary angle-closure glaucoma, depending on the closure of the angle between the cornea and the iris. Principal causes of secondary glaucoma include optic nerve trauma or damage, eye disease, surgery, neovascularization, tumours and use of steroid and sulfa drugs. Risk factors for secondary glaucoma include uveitis, cataract surgery and also intraocular tumours. Common treatments are designed according to the type and the underlying causative condition, in addition to the consequent rise in IOP. These include drug therapy, the use of miotics, surgery or laser therapy.

Manual small incision cataract surgery (MSICS) is an evolution of extracapsular cataract extraction (ECCE); the lens is removed from the eye through a self-sealing scleral tunnel wound. A well-constructed scleral tunnel is held closed by internal pressure, is watertight, and does not require suturing. The wound is relatively smaller than that in ECCE but is still markedly larger than a phacoemulsification wound. Comparative trials of MSICS against phaco in dense cataracts have found no statistically significant difference in outcomes but MSICS had shorter operating times and significantly lower costs. MSICS has become the method of choice in the developing world because it provides high-quality outcomes with less surgically induced astigmatism than ECCE, no suture-related problems, quick rehabilitation, and fewer post-operative visits. MSICS is easy and fast to learn for the surgeon, cost effective, simple, and applicable to almost all types of cataract.

Clear lens extraction, also known as refractive lensectomy, custom lens replacement or refractive lens exchange is a surgical procedure in which clear lens of the human eye is removed. Unlike cataract surgery, where cloudy lens is removed to treat cataract, clear lens extraction is done to surgically correct refractive errors such as high myopia. It can also be done in hyperopic or presbyopic patients who wish to have a multifocal IOL implanted to avoid wearing glasses. It is also used as a treatment for diseases such as angle closure glaucoma.

References

↑ Dimitri T. Azar; Damien Gatinel (2007). Refractive surgery (2nd ed.). Mosby Elsevier. ISBN 978032303599-6.
1 2 de Silva, Samantha R.; Evans, Jennifer R.; Kirthi, Varo; Ziaei, Mohammed; Leyland, Martin (2016). "Multifocal versus monofocal intraocular lenses after cataract extraction". The Cochrane Database of Systematic Reviews. 2016 (12): CD003169. doi:10.1002/14651858.CD003169.pub4. ISSN 1469-493X. PMC 6463930 . PMID 27943250.
1 2 Ong, Hon Shing; Evans, Jennifer R.; Allan, Bruce D. S. (2014-05-01). "Accommodative intraocular lens versus standard monofocal intraocular lens implantation in cataract surgery" (PDF). The Cochrane Database of Systematic Reviews. 2014 (5): CD009667. doi:10.1002/14651858.CD009667.pub2. ISSN 1469-493X. PMC 10505746 . PMID 24788900.

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[azar-1] Dimitri T. Azar; Damien Gatinel (2007). Refractive surgery (2nd ed.). Mosby Elsevier. ISBN 978032303599-6.

[:0-2] 1 2 de Silva, Samantha R.; Evans, Jennifer R.; Kirthi, Varo; Ziaei, Mohammed; Leyland, Martin (2016). "Multifocal versus monofocal intraocular lenses after cataract extraction". The Cochrane Database of Systematic Reviews. 2016 (12): CD003169. doi:10.1002/14651858.CD003169.pub4. ISSN 1469-493X. PMC 6463930 . PMID 27943250.

[:1-3] 1 2 Ong, Hon Shing; Evans, Jennifer R.; Allan, Bruce D. S. (2014-05-01). "Accommodative intraocular lens versus standard monofocal intraocular lens implantation in cataract surgery" (PDF). The Cochrane Database of Systematic Reviews. 2014 (5): CD009667. doi:10.1002/14651858.CD009667.pub2. ISSN 1469-493X. PMC 10505746 . PMID 24788900.

[1]

[2]

[3]