Implantable collamer lens
|Implantable Collamer Lens (ICL)|
Implantable collamer lens or ICL, called by its manufacturer Visian ICL, is a soft, flexible gel-lens used in refractive surgeries for the permanent correction of myopia (nearsightedness), made of a collagen copolymer material, named by combining "collagen" and "polymer". The ICL procedure is a popular alternative to LASIK and PRK since it requires no removal of the corneal tissue and reportedly produces better visual results.
The ICL procedure is a type of refractive surgery performed by an ophthalmologist in which the ICL is surgically implanted inside the eye, where it resides permanently. The ICL requires no maintenance after the procedure and functions very similarly to contact lenses in improving visual acuity. For most patients, ICL provides permanent freedom from eyeglasses or contact lenses.
In 1953, Italian surgeon Benedetto Strampelli became the first to successfully implant a phakic intra-ocular lens (IOL) in the anterior chamber of the eye for the correction of myopia. That first pIOL was manufactured by the Rayner company of Brighton, East Sussex, England from Perspex CQ Polymethylmethacrylate (PMMA) made by ICI (Imperial Chemical Industries). 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). In 1959, Dr. Joachin Barracher reported the results of 239 implantations. However, the complications in these clinical trials necessitated explantation for many cases due to problems such as chronic loss of corneal endothelial cells, iris retraction and atrophy, peripheral anterior synechiae and pupil ovalization. By the 1980s, many PMMA angle-supported anterior chamber pIOLs were phased out of the market because of unacceptable complication rates and replaced with foldable models. Relevant designs include the ZB and the ZB5M by the Domilens Corporation and the NuVita MA 20 by Bausch and Lomb. Foldable models allow for the insertion of the pIOL through a smaller incision, thus reducing the probability of surgically induced astigmatism. Complications arising from anterior chamber angle-supported pIOLs has led to movement toward the posterior chamber. The rationale was based on the theory that there would be a greater distance between the pIOL and the corneal endothelium. This location would also theoretically reduce the incidence of halos and glare as margins of the pupil would cover the border of the optical zones. In 1986, Fyodorov designed the first posterior chamber pIOL in the "collar-button" or "mushroom" configuration and manufactured the pIOL from silicone. The most widely used posterior chamber pIOL is the Visian ICL V4, an implantable collamer lens manufactured by Staar Surgical Companies. The implantable collamer lenses, formerly known as Implantable Contact Lenses, were approved by the U.S. Food and Drug Administration (FDA) in 2005. The FDA requested that the term Implantable Contact Lenses be changed to avoid confusion with corneal contact lenses. By the 21st century, approximately 300,000 ICLs have been implanted in the United States.
Comparison to LASIK
Another type of refractive surgery is LASIK or Lasik (laser-assisted in situ keratomileusis) which changes the shape of the cornea permanently in order to improve visual acuity. The difference between LASIK and the ICL is the area of the eye that is changed in the surgery. LASIK operates on the cornea and the ICL inserts a lens in the posterior chamber of the eye which maintains the structure of the cornea. The ICL can be removed and replaced if vision changes substantially after the procedure. Also many cases of Keratoconus have been reported with Lasik, which is not possible with ICL. Similar types of phakic IOLs are available, such as ones made of the same type of plastic that has been used to make intraocular lenses for cataract surgery.
Insertion of an ICL for the treatment of high myopia is the most commonly performed eye surgical procedure. The procedure is performed under local anesthesia with the patient awake throughout the operation. The flexibility of the ICL enables the lens to be rolled for insertion into the soft silicone tip of the micro incision injector through a very small incision (2.2mm) thus avoiding the need for stitches, and this procedure usually takes less than 30 minutes in the hands of an experienced ophthalmologist.Following the procedure, most people have immediate use of their eyes. The full recovery period is typically 1–2 days with minimal discomfort and most patients are able to go to work the next day. After surgery, the common advice is to avoid driving home and to visit the attending ophthalmologists regularly for several months so as to monitor the implants.
ICL implantation carries several risks associated with eye surgeries, such as the development of small cloudy areas of opacities on the crystalline lens which could occur if the lens is touched during the surgery, increased rate of endothelial cell loss from the back surface of the cornea, and increased pressure inside of the eye. To minimize pressure in the eye post-op, drops are usually applied to the eye, or the creation of an additional peripheral iridotomy may be necessary to improve fluid flow. Additionally, short-term irritations include conjunctiva irritation, corneal swelling, infections, non-reactive pupil, and irritation of the iris. Usually these irritations are transient in nature. Despite these risks, a systematic review of studies has determined that the procedure is safer than conventional laser eye treatment.
Design and materials used for implantable collamer lens
ICLs consists of a small biocompatible intraocular lens (IOL), also known as a posterior chamber phakic intraocular lens (PIOLs), with distinct footplates, called haptics, to hold the lens in place within the cilliary sulcus inside the eye and the anterior vault designed to minimize contact with the eye’s crystalline lens. ICLs are made of a flexible material proprietary hydrophilic porcine collagen (<0.1%) hydroxyethyl methacrylate (HEMA) termed Collamer for short. This material attracts the natural deposition of a layer of fibronectin on the ICL surface that inhibits aqueous protein binding and makes the ICL invisible to the immune system. The Visian ICL V4 is a rectangular single-piece pIOL 7.5 to 8.0mm wide, available in 4 lengths. The optic diameter is between 4.65 to 5.5 mm in myopic ICLs. The Visian ICL V4 was developed to address the issue of vaulting. A higher vault provides greater space between the ICL and crystalline lens to prevent contact between the two lenses and also allows for fluid change of nutrients. ICLs fitted today are fixed monofocal lenses used to correct moderate to high myopia from between -3 to -20 diopters for patients between the ages of 21-45.
Definition of phakic, aphakic and pseudophakic IOLs
- Phakia is the presence of the natural crystalline lens. ICLs are lenses that are surgically placed in front of the natural crystalline lens. Thus the ICL and the natural lens work in conjunction for vision.
- Aphakia is the absence of the natural crystalline lens, either from natural causes or from removal.
- Pseudophakia is the substitution of the natural crystalline lens with a synthetic lens. Pseudophakic IOLs are used when cataracts have developed in the eye and the natural lens must be replaced with IOLs.
The root of these words comes from the Greek word phakos 'lens'.
Insertion of an ICL for the treatment of high myopia is the most commonly performed eye surgical procedure. The procedure is performed under local anesthesia with the patient awake throughout the operation. The flexibility of the ICL enables the lens to be rolled for insertion into the soft silicone tip of the micro incision injector through a very small incision (2.2mm) thus avoiding the need for stitches. Once injected, the ICL unfolds in the eye and the haptics are gently pushed under the iris with a blunt spatula. A peripheral iridectomy is performed to prevent pupillary block and finally the wound is hydrated.
This procedure usually takes less than 30 minutes in the hands of an experienced ophthalmologist.
Prior to the surgery, the ICL must be loaded into the microinjector cartridge. The lenses are checked under an operating microscope to ensure correct anterior-posterior orientation before they are loaded into the injector with the dome side of the lens facing up to avoid damage to the haptic legs.
Following the procedure, most people have immediate use of their eyes. The full recovery period is typically 1–2 days with minimal discomfort and most people are able to go to work the next day. After surgery, the common advice is to avoid driving home and to visit the attending ophthalmologists regularly for several months so as to monitor the implants.
Candidates for procedure
- Suffer from moderate to high myopia(nearsightedness) of -3 to -20 diopters.
- Are not good candidates for LASIK because they have thin corneas.
A person is not a good candidate for phakic lenses if they:
- Have a disease or are on medications that may affect wound healing. Certain conditions, such as autoimmune diseases (e.g., lupus, rheumatoid arthritis), immunodeficiency states (e.g., HIV) and diabetes, and some medications (e.g., retinoic acid and steroids) may prevent proper healing after intraocular surgery.
- Have a high risk of eye trauma. A blow to the head or a hit in the eye may cause the eye to be susceptible to rupture.
- Have large pupils. If one's pupil dilates in low lighting conditions to a size that is larger than the size of the lens, one has a higher risk of experiencing visual disturbances after surgery that may affect one's ability to function comfortably or normally under such conditions (e.g., while driving at night).
- Have glaucoma
- Had eye injury or previous eye surgery.
- Have the need for visual correction outside the range for which the phakic lens has been approved.
- Are over the age of 45 years old. ICLs have not been studied in patients over the age of 45.
The FDA website on phakic IOL surgery states,
What to expect before, during and after surgery will vary according to the type of phakic lens implanted, the practices of the medical facility where the surgery will be performed and of the doctor who will be providing your care, and your unique health circumstances and body's response.
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