Intraocular lens
Encyclopedia
An intraocular lens is an implanted lens
in the eye
, usually replacing the existing crystalline lens
because it has been clouded over by a cataract
, or as a form of refractive surgery
to change the eye's optical power
. It usually consists of a small plastic
lens with plastic side struts, called haptics, to hold the lens in place within the capsular bag inside the eye. IOLs were traditionally made of an inflexible material (PMMA), although this has largely been superseded by the use of flexible materials. Most IOLs fitted today are fixed monofocal lenses matched to distance vision. However, other types are available, such as multifocal IOLs which provide the patient with multiple-focused vision at far and reading distance, and adaptive IOLs which provide the patient with limited visual accommodation.
Insertion of an intraocular lens for the treatment of cataracts is the most commonly performed eye surgical
procedure. The procedure can be done under local anesthesia with the patient awake throughout the operation. The use of a flexible IOL enables the lens to be rolled for insertion into the capsule through a very small incision, thus avoiding the need for stitches, and this procedure usually takes less than 30 minutes in the hands of an experienced ophthalmologist. The recovery period is about 2–3 weeks. After surgery, patients should avoid strenuous exercise or anything else that significantly increases blood pressure. They should also visit their ophthalmologists regularly for several months so as to monitor the implants.
IOL implantation carries several risks associated with eye surgeries, such as infection, loosening of the lens, lens rotation, inflammation and night time halos, but a systematic review of studies has determined that the procedure is safer than conventional laser eye treatment. Though IOLs enable many patients to have reduced dependence on glasses, most patients still rely on glasses for certain activities, such as reading.
Sir Harold Ridley
was the first to successfully implant an intraocular lens on November 29, 1949, at St Thomas' Hospital
at London
. That first intraocular lens was manufactured by the Rayner
company of Brighton, East Sussex, England from Perspex CQ Polymethylmethacrylate (PMMA) made by ICI (Imperial Chemical Industries). It is said the idea of implanting an intraocular lens came to him after an intern asked him why he was not replacing the lens he had removed during cataract surgery. The acrylic plastic material was chosen because Harold Ridley noticed that it was inert, after seeing RAF (Royal air Force) pilots of World War II with pieces of shattered canopies in their eyes (this acrylic resin is known by several trade names including Lucite and Plexiglas). The intraocular lens did not find widespread acceptance in cataract surgery until the 1970s, when further developments in lens design and surgical techniques had come about. By the 21st century, more than a million IOLs are implanted annually in the United States.
observed that Royal Air Force
pilots who sustained eye injuries
during World War II
involving PMMA windshield material did not show any rejection or foreign body
reaction. Deducing that the transparent material was inert and useful for implantation in the eye, Ridley designed and implanted the first intraocular lens in a human eye.
Advances in technology have brought about the use of silicone
and acrylic
, both of which are soft foldable inert materials. This allows the lens to be folded and inserted into the eye through a smaller incision. PMMA and acrylic lenses can also be used with small incisions and are a better choice in people who have a history of uveitis
, have diabetic retinopathy
requiring vitrectomy
with replacement by silicone oil or are at high risk of retinal detachment.
In the United States, a new category of intraocular lenses was opened with the approval by the Food and Drug Administration in 2003 of multifocal and accommodating lenses. These come at an additional cost to the recipient beyond what Medicare will pay and each has advantages and disadvantages.
New FDA-approved multifocal intraocular lens implants allow most post operative cataract patients the advantage of glass-free vision. These new multifocal lenses are not a covered expense under most insurance plans (In the United States, Medicare decided to stop covering them in May 2005) and can cost the patient upwards of $2800 per eye. Latest advances include IOLs with square-edge design, non-glare edge design and yellow dye added to the IOL.
The trade marked "Natural Yellow" this material is relatively new to the market and available in three hydrophilic IOL materials. Dr. Patrick H. Benz of Benz Research and Development created the first IOL material to incorporate the same UV-A blocking and violet light filtering chromophore
that is in the human crystalline lens. This break through material provides the exact chromophore
the human retina has already specified for light protection.
Multifocal IOLs - provide for simultaneous viewing of both distance vision and near vision. Some patients report glare and halos at night time with these lenses.
Accommodating IOLs - allow for both distance vision and midrange near vision. These IOLs are typically not as strong for closer vision as the multifocal IOLs.
To incorporate the strengths of each type of IOL, some eye surgeons recommend using a multifocal IOL in one eye to emphasize close reading vision and an accommodating IOL in the other eye for further midrange vision. This is called "mix and match." Distance vision is not compromised with this approach, while near vision is optimized.
Other IOLs include:
The root of these words comes from the Greek word phakos 'lens'.
eyes. This type of IOL is also called PIOL (phakic intraocular lens), and the crystalline lens is not removed.
More commonly, aphakic IOLs (that is, not PIOLs) are implanted via Clear Lens Extraction and Replacement (CLEAR) surgery. During CLEAR, the crystalline lens is extracted and an IOL replaces it in a process that is very similar to cataract surgery: both involve lens replacement, local anesthesia, both last approximately 30 minutes, and both require making a small incision in the eye for lens insertion. People recover from CLEAR surgery 1–7 days after the operation. During this time, they should avoid strenuous exercise or anything else that significantly raises blood pressure. They should also visit their ophthalmologists regularly for several months so as to monitor the IOL implants.
CLEAR has a 90% success rate (risks include wound leakage, infection, inflammation, and astigmatism). CLEAR can only be performed on patients ages 40 and older. This is to ensure that eye growth, which disrupts IOL lenses, will not occur post-surgery.
Once implanted, IOL lenses have three major benefits. First, they are an alternative to LASIK
, a form of eye surgery that does not work for people with serious vision problems. Effective IOL implants also entirely eliminate the need for glasses or contact lenses post-surgery for most patients. The cataract will not return, as the lens has been removed. The disadvantage is that the eye's ability to change focus (accommodate) has generally been reduced or eliminated, depending on the kind of lens implanted.
Most PIOLs have not yet been approved by FDA, but many are under investigation, and some of the risks that FDA have been found so far during a three year study of the Artisan Myopia lens (FDA approved in 2004), produced by Ophtec USA Inc, are:
Other risks include:
One of the causes of the risks above is that the lens can rotate inside the eye, because the PIOL is too short, or because the sulcus
has a slightly oval shape (the height is slightly smaller than the width).
According to placement site in the eyes phakic IOLs can be divided to:
, or change focus from near to far, far to near, and to distances in between. Accommodating IOLs interact with ciliary muscle
s and zonules, using hinges at both ends to “latch on” and move forward and backward inside the eye using the same mechanism as normal accommodation. These IOLs have a 4.5-mm square-edged optic and a long hinged plate design with polyimide loops at the end of the haptics. The hinges are made of an advanced silicone
called BioSil that was thoroughly tested to make sure it was capable of unlimited flexing in the eye.
There are many advantages to accommodating IOLs. For instance, light comes from and is focused on a single focal point, reducing halos, glares, and other visual aberrations. Accommodating IOLs provide excellent vision at all distances (far, intermediate, and near), project no unwanted retinal images, and produce no loss of contrast sensitivity or central system adaptation. Accommodating IOLs have the potential to eliminate or reduce the dependence on glasses after cataract surgery. For some, accommodating IOLs may be a better alternative to refractive lens exchange (RLE
) and monovision.
The FDA approved Eyeonics Inc.’s accommodating IOL, Crystalens AT-45, in November 2003. Bausch & Lomb
acquired Crystalens in 2008 and introduced a newer model called Crystalens HD in 2008. Crystalens is the only FDA-approved accommodating IOL currently on the market and it is approved in the United States and Europe.
Studies and Peer Reviews:
In a September 2004 FDA trial involving 325 patients :
Criticisms:
Candidates:
Generally, patients over 50 with cataract problems and no serious eye diseases are good candidates for the procedure.
The patient must have functional ciliary muscles or zonules for haptics positioning. In addition, the pupils must dilate adequately, as the IOL will induce glares in low-light environments if the pupils dilate too large. Accommodating IOLs are beneficial not only for patients with cataracts, but also those who wish to reduce their dependency on glasses and contacts due to myopia
, hyperopia
and presbyopia
.
Post-operative care is similar to that of normal IOLs. However, patients must include ophthalmologic exercises such as puzzles and word games as a part of their daily regimen in order to tone up their ciliary muscles and attain the maximum benefit from the accommodating lenses. These exercises should be done consistently for 3–6 months and the patient's performance monitored by their eye care professional.
Other promising multifocal/accommodating IOLs currently in clinical trials include Accommodative 1CU (HumanOptics, Erlangen, Germany), Smartlens (Medennium, Irvine, CA), and dual optic accommodating lenses such as Sarfarazi (Bausch and Lomb, Rochester, NY) and Synchrony
(Abbott Laboratories, Abbott Park, IL).
Synchrony IOL is anticipated to receive FDA approval in 2012.
Thomas A Oetting, MS MD
Professor of Clinical Ophthalmology
Director Ophthalmology Residency Program
University of Iowa
Chief of Eye Service and Deputy Director of Surgery Service
Surgical videos
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
in the eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
, usually replacing the existing crystalline lens
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...
because it has been clouded over by a cataract
Cataract
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
, or as a form of refractive surgery
Refractive surgery
Refractive eye surgery is any eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea or cataract surgery. The most common methods today use excimer lasers to...
to change the eye's optical power
Optical power
Optical power is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device. The dioptre is the most common unit of measurement of optical power...
. It usually consists of a small plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
lens with plastic side struts, called haptics, to hold the lens in place within the capsular bag inside the eye. IOLs were traditionally made of an inflexible material (PMMA), although this has largely been superseded by the use of flexible materials. Most IOLs fitted today are fixed monofocal lenses matched to distance vision. However, other types are available, such as multifocal IOLs which provide the patient with multiple-focused vision at far and reading distance, and adaptive IOLs which provide the patient with limited visual accommodation.
Insertion of an intraocular lens for the treatment of cataracts is the most commonly performed eye surgical
Eye surgery
Eye surgery, also known as orogolomistician surgery or ocular surgery, is surgery performed on the eye or its adnexa, typically by an ophthalmologist.-Preparation and precautions:...
procedure. The procedure can be done under local anesthesia with the patient awake throughout the operation. The use of a flexible IOL enables the lens to be rolled for insertion into the capsule through a very small incision, thus avoiding the need for stitches, and this procedure usually takes less than 30 minutes in the hands of an experienced ophthalmologist. The recovery period is about 2–3 weeks. After surgery, patients should avoid strenuous exercise or anything else that significantly increases blood pressure. They should also visit their ophthalmologists regularly for several months so as to monitor the implants.
IOL implantation carries several risks associated with eye surgeries, such as infection, loosening of the lens, lens rotation, inflammation and night time halos, but a systematic review of studies has determined that the procedure is safer than conventional laser eye treatment. Though IOLs enable many patients to have reduced dependence on glasses, most patients still rely on glasses for certain activities, such as reading.
History
Harold Ridley (ophthalmologist)
Sir Nicholas Harold Lloyd Ridley was an English ophthalmologist who pioneered artificial intraocular lens transplant surgery for cataract patients.-Early years:...
was the first to successfully implant an intraocular lens on November 29, 1949, at St Thomas' Hospital
St Thomas' Hospital
St Thomas' Hospital is a large NHS hospital in London, England. It is administratively a part of Guy's & St Thomas' NHS Foundation Trust. It has provided health care freely or under charitable auspices since the 12th century and was originally located in Southwark.St Thomas' Hospital is accessible...
at London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
. That first intraocular lens was manufactured by the Rayner
Rayner (company)
Rayner based in Brighton & Hove East Sussex is a British manufacturer of intraocular lenses and associated surgical instruments. With Sir Harold Ridley, they were pioneers in the field from 1949 when Ridley successfully implanted the first intraocular lens at St Thomas' Hospital, London.- The...
company of Brighton, East Sussex, England from Perspex CQ Polymethylmethacrylate (PMMA) made by ICI (Imperial Chemical Industries). It is said the idea of implanting an intraocular lens came to him after an intern asked him why he was not replacing the lens he had removed during cataract surgery. The acrylic plastic material was chosen because Harold Ridley noticed that it was inert, after seeing RAF (Royal air Force) pilots of World War II with pieces of shattered canopies in their eyes (this acrylic resin is known by several trade names including Lucite and Plexiglas). The intraocular lens did not find widespread acceptance in cataract surgery until the 1970s, when further developments in lens design and surgical techniques had come about. By the 21st century, more than a million IOLs are implanted annually in the United States.
Materials used for intraocular lenses
Polymethylmethacrylate (PMMA) was the first material to be used successfully in intraocular lenses. British ophthalmologist Sir Harold RidleyHarold Ridley (ophthalmologist)
Sir Nicholas Harold Lloyd Ridley was an English ophthalmologist who pioneered artificial intraocular lens transplant surgery for cataract patients.-Early years:...
observed that Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
pilots who sustained eye injuries
Eye injury
Physical or chemical injuries of the eye can be a serious threat to vision if not treated appropriately and in a timely fashion. The most obvious presentation of ocular injuries is redness and pain of the affected eyes. This is not, however, universally true, as tiny metallic projectiles may cause...
during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
involving PMMA windshield material did not show any rejection or foreign body
Foreign body
A foreign body is any object originating outside the body. In machinery, it can mean any unwanted intruding object.Most references to foreign bodies involve propulsion through natural orifices into hollow organs....
reaction. Deducing that the transparent material was inert and useful for implantation in the eye, Ridley designed and implanted the first intraocular lens in a human eye.
Advances in technology have brought about the use of silicone
Silicone
Silicones are inert, synthetic compounds with a variety of forms and uses. Typically heat-resistant and rubber-like, they are used in sealants, adhesives, lubricants, medical applications , cookware, and insulation....
and acrylic
Acrylic glass
Poly is a transparent thermoplastic, often used as a light or shatter-resistant alternative to glass. It is sometimes called acrylic glass. Chemically, it is the synthetic polymer of methyl methacrylate...
, both of which are soft foldable inert materials. This allows the lens to be folded and inserted into the eye through a smaller incision. PMMA and acrylic lenses can also be used with small incisions and are a better choice in people who have a history of uveitis
Uveitis
Uveitis specifically refers to inflammation of the middle layer of the eye, termed the "uvea" but in common usage may refer to any inflammatory process involving the interior of the eye....
, have diabetic retinopathy
Diabetic retinopathy
Diabetic retinopathy is retinopathy caused by complications of diabetes mellitus, which can eventually lead to blindness....
requiring vitrectomy
Vitrectomy
Vitrectomy is a surgery to remove some or all of the vitreous humor from the eye. Anterior vitrectomy entails removing small portions of the vitreous from the front structures of the eye—often because these are tangled in an intraocular lens or other structures...
with replacement by silicone oil or are at high risk of retinal detachment.
In the United States, a new category of intraocular lenses was opened with the approval by the Food and Drug Administration in 2003 of multifocal and accommodating lenses. These come at an additional cost to the recipient beyond what Medicare will pay and each has advantages and disadvantages.
New FDA-approved multifocal intraocular lens implants allow most post operative cataract patients the advantage of glass-free vision. These new multifocal lenses are not a covered expense under most insurance plans (In the United States, Medicare decided to stop covering them in May 2005) and can cost the patient upwards of $2800 per eye. Latest advances include IOLs with square-edge design, non-glare edge design and yellow dye added to the IOL.
The trade marked "Natural Yellow" this material is relatively new to the market and available in three hydrophilic IOL materials. Dr. Patrick H. Benz of Benz Research and Development created the first IOL material to incorporate the same UV-A blocking and violet light filtering chromophore
Chromophore
A chromophore is the part of a molecule responsible for its color. The color arises when a molecule absorbs certain wavelengths of visible light and transmits or reflects others. The chromophore is a region in the molecule where the energy difference between two different molecular orbitals falls...
that is in the human crystalline lens. This break through material provides the exact chromophore
Chromophore
A chromophore is the part of a molecule responsible for its color. The color arises when a molecule absorbs certain wavelengths of visible light and transmits or reflects others. The chromophore is a region in the molecule where the energy difference between two different molecular orbitals falls...
the human retina has already specified for light protection.
Multifocal IOLs - provide for simultaneous viewing of both distance vision and near vision. Some patients report glare and halos at night time with these lenses.
Accommodating IOLs - allow for both distance vision and midrange near vision. These IOLs are typically not as strong for closer vision as the multifocal IOLs.
To incorporate the strengths of each type of IOL, some eye surgeons recommend using a multifocal IOL in one eye to emphasize close reading vision and an accommodating IOL in the other eye for further midrange vision. This is called "mix and match." Distance vision is not compromised with this approach, while near vision is optimized.
Other IOLs include:
- Blue Light Filtering IOLs filter the UV and high-energy blue light present in natural and artificial light, both of which can cause vision problems; however too much filtering of blue light can increase depression, especially in the winter months (SAD).
- ToricToric lensA toric lens is a lens with two different powers in two orientations perpendicular to each other. One of the lens surfaces is shaped like a "cap" from a torus , while the other one usually is spherical...
IOLs (1998) correct astigmatic vision.
Phakic, aphakic and pseudophakic IOLs
- Phakia is the presence of the natural crystalline lens.
- AphakiaAphakiaAphakia is the absence of the lens of the eye, due to surgical removal, a perforating wound or ulcer, or congenital anomaly. It causes a loss of accommodation, hyperopia, and a deep anterior chamber. Complications include detachment of the vitreous or retina, and glaucoma.Aphakic people are...
is the absence of the natural crystalline lens, either from natural causes or because it has been removed. - Pseudophakia is the substitution of the natural crystalline lens with a synthetic lens. Pseudophakic IOLs are used in cataract surgery.
The root of these words comes from the Greek word phakos 'lens'.
Intraocular lenses for correcting refractive errors
Intraocular lenses have been used since 1999 for correcting larger errors in myopic (near-sighted), hyperopic (far-sighted), and astigmaticAstigmatism (eye)
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. There are two types of astigmatism: regular and...
eyes. This type of IOL is also called PIOL (phakic intraocular lens), and the crystalline lens is not removed.
More commonly, aphakic IOLs (that is, not PIOLs) are implanted via Clear Lens Extraction and Replacement (CLEAR) surgery. During CLEAR, the crystalline lens is extracted and an IOL replaces it in a process that is very similar to cataract surgery: both involve lens replacement, local anesthesia, both last approximately 30 minutes, and both require making a small incision in the eye for lens insertion. People recover from CLEAR surgery 1–7 days after the operation. During this time, they should avoid strenuous exercise or anything else that significantly raises blood pressure. They should also visit their ophthalmologists regularly for several months so as to monitor the IOL implants.
CLEAR has a 90% success rate (risks include wound leakage, infection, inflammation, and astigmatism). CLEAR can only be performed on patients ages 40 and older. This is to ensure that eye growth, which disrupts IOL lenses, will not occur post-surgery.
Once implanted, IOL lenses have three major benefits. First, they are an alternative to LASIK
LASIK
LASIK or Lasik , commonly referred to simply as laser eye surgery, is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism...
, a form of eye surgery that does not work for people with serious vision problems. Effective IOL implants also entirely eliminate the need for glasses or contact lenses post-surgery for most patients. The cataract will not return, as the lens has been removed. The disadvantage is that the eye's ability to change focus (accommodate) has generally been reduced or eliminated, depending on the kind of lens implanted.
Most PIOLs have not yet been approved by FDA, but many are under investigation, and some of the risks that FDA have been found so far during a three year study of the Artisan Myopia lens (FDA approved in 2004), produced by Ophtec USA Inc, are:
- a yearly loss of 1.8% of the endothelial cells,
- 0.6% risk of retinal detachmentRetinal detachmentRetinal detachment is a disorder of the eye in which the retina peels away from its underlying layer of support tissue. Initial detachment may be localized, but without rapid treatment the entire retina may detach, leading to vision loss and blindness. It is a medical emergency.The retina is a...
, - 0.6% risk of cataractCataractA cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
(other studies have shown a risk of 0.5 - 1.0%), and - 0.4% risk of corneal swelling.
Other risks include:
- 0.03 - 0.05% eye infection risk, which in worst case can lead to blindnessBlindnessBlindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
. This risk exists in all eye surgery procedures, and is not unique for IOLs. - glaucomaGlaucomaGlaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
, - astigmatismAstigmatism (eye)Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. There are two types of astigmatism: regular and...
, - remaining near or far sightedness,
- rotation of the lens inside the eye within one or two days after surgery.
One of the causes of the risks above is that the lens can rotate inside the eye, because the PIOL is too short, or because the sulcus
Sulcus (anatomy)
A sulcus is a depression or fissure in the surface of an organ, especially the brain.-Elsewhere:* anterior interventricular sulcus* calcaneal sulcus* coronal sulcus* gingival sulcus* gluteal sulcus* interlabial sulci...
has a slightly oval shape (the height is slightly smaller than the width).
Types of PIOLs
Phakic IOLS (PIOLs) can be either spheric or toric—the latter is used for astigmatic eyes. The difference is that toric PIOLs have to be inserted in a specific angle, or the astigmatism will not be fully corrected, or it can even get worse.According to placement site in the eyes phakic IOLs can be divided to:
- Angle supported PIOLs: those IOLs are placed in the anterior chamber. They are notorious for their negative impact on the corneal endothelial lining, which is vital for maintaining a healthy dry cornea.
- Iris supported PIOLs: this type is gaining more and more popularity. The IOL is attached by claws to the mid peripheral iris by a technique called enclavation. It is believed to have a lesser effect on corneal endothelium.
- Sulcus supported PIOLs: these IOLS are placed in the posterior chamber in front of the natural crystalline lens. They have special vaulting so as not to be in contact with the normal lens. The main complications with this type is their tendency to cause cataracts and/or pigment dispersion.
Accommodating IOLs
One of the major disadvantages of conventional IOLs is that they are primarily focused for distance vision. Though patients who undergo a standard IOL implantation no longer experience clouding from cataracts, they are unable to accommodateAccommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
, or change focus from near to far, far to near, and to distances in between. Accommodating IOLs interact with ciliary muscle
Ciliary muscle
The ciliary muscle is a ring of striated smooth muscle in the eye's middle layer that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm's canal. It changes the shape of the lens within the eye not the size of the pupil which is...
s and zonules, using hinges at both ends to “latch on” and move forward and backward inside the eye using the same mechanism as normal accommodation. These IOLs have a 4.5-mm square-edged optic and a long hinged plate design with polyimide loops at the end of the haptics. The hinges are made of an advanced silicone
Silicone
Silicones are inert, synthetic compounds with a variety of forms and uses. Typically heat-resistant and rubber-like, they are used in sealants, adhesives, lubricants, medical applications , cookware, and insulation....
called BioSil that was thoroughly tested to make sure it was capable of unlimited flexing in the eye.
There are many advantages to accommodating IOLs. For instance, light comes from and is focused on a single focal point, reducing halos, glares, and other visual aberrations. Accommodating IOLs provide excellent vision at all distances (far, intermediate, and near), project no unwanted retinal images, and produce no loss of contrast sensitivity or central system adaptation. Accommodating IOLs have the potential to eliminate or reduce the dependence on glasses after cataract surgery. For some, accommodating IOLs may be a better alternative to refractive lens exchange (RLE
RLE
RLE could refer to:*Run-length encoding*Real life experience*Research Laboratory of Electronics at MIT*Right-to-left embedding, a Unicode format character controlling text direction...
) and monovision.
The FDA approved Eyeonics Inc.’s accommodating IOL, Crystalens AT-45, in November 2003. Bausch & Lomb
Bausch & Lomb
Bausch & Lomb, an American company based in Rochester, New York, is one of the world's leading suppliers of eye health products, such as contact lenses and lens care products today. In addition to this main activity, in recent years the area of medical technology has been developed...
acquired Crystalens in 2008 and introduced a newer model called Crystalens HD in 2008. Crystalens is the only FDA-approved accommodating IOL currently on the market and it is approved in the United States and Europe.
Studies and Peer Reviews:
In a September 2004 FDA trial involving 325 patients :
- 100% could see at intermediate distances (24" to 30") without glasses; the distance for most of life's activities
- 98.4% could see well enough to read the newspaper and the phone book without glasses.
- Some patients did require glasses for some tasks after implantation of the crystalens
- Vision was restored to 20/40 or better in 88% of patients compared to 35.9% of patients who received normal IOLs.
- In 2006, a 12 month study by Cummings et al. investigated contrast sensitivity and near visual acuity in patients who had received a Crystalens AT-45 versus those who received a standard IOL. Effectiveness was measured in terms of near, intermediate, and distance visual acuities and safety was evaluated by assessing complications. The study concluded that contrast sensitivity was not reduced compared to those receiving standard IOLs and provided good visual acuity at all distances in pseudophakic patients. There were no adverse complications reported. However, this study lacked a long-term follow up.
- Pepose et al. (2007) tested the combination of a multifocal IOL in one eye and an accommodating IOL in the other eye. The group found that any combination of Crystalens in one or both eyes was better for intermediate vision. ReSTOR (multifocal IOL) is better for near vision. The Crystalens and ReSTOR combination had better mean intermediate and near vision overall.
- Macsai et al. (2006) conducted a multicenter, nationwide study evaluating the visual outcomes of 112 cataract patients implanted with Crystalens IOL (n=56) versus standard monofocal IOLs (n=56). The Crystalens group demonstrated significantly better visual acuity compared to the monofocal patient group, as well as better distance and near vision 6 months post-operation.
- In overall FDA clinical results on uncorrected binocular vision in 124 patients, 92 per cent had distance vision of 20/25 or better, 98 per cent had intermediate vision of 20/25 or better, and 73 per cent had near vision of 20/25 or better 11 to 15 months after surgery. In addition, 73.5 per cent either did not wear spectacles or wore them most none of the time.
- Sanders et al. (2007) published visual performance results after Tetraflex accommodative intraocular lens implantation. They found that 6 months post-operatively, all patients had at least 1 diopter of accommodative amplitude. At 6 months, 92.2 per cent of eyes had 20/40 or better uncorrected distance visual acuity (UCDVA) and 50.6 per cent of eyes achieved 20/20 or better UCDVA. At near, 48.1 per cent of eyes achieved 20/40 or better uncorrected near visual acuity.
- However, at this time, there no long-term, well-designed clinical trials to support the accommodating technology of the Crystalens IOL.
Criticisms:
- The main concern with accommodating IOLs is that there are no long-term, large-scale studies involving its use in patients. Such clinical studies using objective measurement techniques must be done to fully support the claim that accommodating IOLs can restore accommodative vision to the presbyopic eye.
- Though it is rare, potential complications include capsular bag contraction and posterior capsule opacification.
- It is more difficult to implant an accommodating IOL (due to the attachment of hinges) and recovery time may be longer than with a standard IOL.
- Patients should expect that his or her accommodative abilities will not be restored to perfect or near perfect function. Though vision is significantly improved, the degree of improvement will not be the same for all and some will still need glasses after surgery.
- Accommodating IOLs are expensive. Insurance companies do not cover these technologically advanced IOLs because long-term efficacy is still being determined.
- Older patients may not have the muscle strength to fully accommodate with the IOL. The longer the patient has compensated for presbyopia with reading glasses, the weaker the muscles used in accommodation are likely to be. If the patient cannot fully accommodate, reading glasses will still be needed.
Candidates:
Generally, patients over 50 with cataract problems and no serious eye diseases are good candidates for the procedure.
The patient must have functional ciliary muscles or zonules for haptics positioning. In addition, the pupils must dilate adequately, as the IOL will induce glares in low-light environments if the pupils dilate too large. Accommodating IOLs are beneficial not only for patients with cataracts, but also those who wish to reduce their dependency on glasses and contacts due to myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
, hyperopia
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...
and presbyopia
Presbyopia
Presbyopia is a condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Presbyopia’s exact mechanisms are not known with certainty; the research evidence most strongly supports a loss of elasticity of the crystalline lens, although changes in the...
.
Post-operative care is similar to that of normal IOLs. However, patients must include ophthalmologic exercises such as puzzles and word games as a part of their daily regimen in order to tone up their ciliary muscles and attain the maximum benefit from the accommodating lenses. These exercises should be done consistently for 3–6 months and the patient's performance monitored by their eye care professional.
Other promising multifocal/accommodating IOLs currently in clinical trials include Accommodative 1CU (HumanOptics, Erlangen, Germany), Smartlens (Medennium, Irvine, CA), and dual optic accommodating lenses such as Sarfarazi (Bausch and Lomb, Rochester, NY) and Synchrony
(Abbott Laboratories, Abbott Park, IL).
Synchrony IOL is anticipated to receive FDA approval in 2012.
See also
- AphakiaAphakiaAphakia is the absence of the lens of the eye, due to surgical removal, a perforating wound or ulcer, or congenital anomaly. It causes a loss of accommodation, hyperopia, and a deep anterior chamber. Complications include detachment of the vitreous or retina, and glaucoma.Aphakic people are...
- CapsulorhexisCapsulorhexisCapsulorhexis is a technique used to remove the lens capsule during cataract surgery. The spelling has varied between having one or two 'r's. It generally refers to removal of a part of the anterior lens capsule, but in situations like a developmental cataract a part of the posterior capsule is...
- Contact lensContact lensA contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...
- Adjustable-focus eyeglassesAdjustable-focus eyeglassesAdjustable focus eyeglasses are prescription eyeglasses with an adjustable focal length. They compensate for refractive errors by providing variable focusing, allowing users to adjust them for desired distance or prescription, or both....
- Bates methodBates MethodThe Bates method is an alternative therapy aimed at improving eyesight. Eye-care physician William Horatio Bates attributed nearly all sight problems to habitual strain of the eyes, and felt that glasses were harmful and never necessary...
Manufacturers of IOL
- http://www.oculentis.com / Optimal solutions for the eye surgeon and the patient international company based in Germany.
- http://www.aurolab.com/ IOL manufacturer and exporter, based in India
- http://www.rayner.com/home/ The World's first IOL manufacturer based in The United Kingdom
- http://www.amo-inc.com/ Abbott Medical Optics Inc. is an IOL manufacturer based in USA
- http://latan.info/ IOL Manufacturer in Russian Federation.
- http://www.benzrd.com/ IOL Manufacturer in USA
- http://www.hoya.co.jp/english/index.html Hoya is an IOL manufacturer based in Japan
- http://www.staar.com/ IOL Manufacturer in USA
- http://www.vsybiotechnology.com IOL Manufacturer in Turkey
- http://www.globalophthalmic.in/ IOL Manufacturer in India/
- http://www.alcon.com/en/index.asp IOL Manufacturer in USA
- http://www.ophtec.com/ IOL Manufacturer in the Netherlands
- http://www.reper.ru/ IOL Manufacturer in Russia
- http://www.bausch.com/ IOL Manufacturer in USA
External links
http://www.facebook.com/cataract.surgeryThomas A Oetting, MS MD
Professor of Clinical Ophthalmology
Director Ophthalmology Residency Program
University of Iowa
Chief of Eye Service and Deputy Director of Surgery Service
Surgical videos