IOLs – Intraocular Lenses

Today, IOLs are used widely in cataract surgery, but prior to 1945, cataract patients were left aphakic (a state in which the human eye has no lens inside it, mostly due to surgical removal). Patients had to wear very heavy eye glasses in order to see again. Thanks to Sir Harold Ridley, the inventor of the first synthetic lens implantable inside the human eye, that misery is no longer a horrible option to consider for cataract patients.

The following lines will take you in a journey to the fantastic world of IOLs tracing the historical beginning till the modern revolution in the design and capabilities of modern IOLs.

Back to the history

The invention of an intraocular lens came from a genuine observation made by the English ophthalmologist Sir Harold Ridley that PMMA fragments from the cockpits of the windshields of airplanes were will tolerated inside the anterior chambers of the injured pilots during the world war II without causing much complications.

He then designed a biconcave PMMA (polymethylmethacrylate) lens and implanted it in the posterior segment of a female patient after performing extra capsular cataract extraction. He was knighted for his marvelous contribution that stands till today as the solid foundation for the modern revolution in the treatment options available for cataract patients – through a variety of IOL designs offering various capabilities and functionalities to meet all the visual needs of the patients.

The monofocals

These are the basic treatment options available for cataract patients. This type of IOL is capable of correcting one type of refractive error only at a time; either nearsightedness, or farsightedness. The main disadvantage of this type of IOL is that they are not able to restore the accommodative power of the normal crystalline lens which enable humans to see far objects as well as near ones. This means that after surgery you will be able to see far ahead during walking without the need for glasses; on the other hand, you will need to wear prescription glasses to be able to see near, as during reading.

If you have concomitant nearsightedness or farsightedness and astigmatism, this IOL will only correct the main refractive error and you will still have astigmatism after operation. You will need to wear prescription spectacles after the surgery for correcting the astigmatism.

The monofocals are part of the standard cost covered by Medicare if you are under the coverage of Medicare.

The most commonly used types for this genre are:

1. Tecnis monofocal lens implant: The Tecnis monofocal IOL is manufactured by Abbott Medical Optics. It is the only IOL that has an FDA approval for claims in improving functional vision. This means better recognition of various objects under low light conditions. The IOL is manufactured from hydrophobic acrylic material leading to less calcification and opacification of the IOL with the passage of time. The unique design of the IOL allows for reduction of chromatic aberrations compared to other IOLs.

2. Acrysof monofocal lens implant: The Acrysof monofocal lens implant is produced by Alcon Laboratories. The normal human crystalline lens has the ability to filter the high energy blue light in order not to cause harmful impacts on the delicate retina as a disease known as age related macular degeneration. Unfortunately, this feature is lost when the cataractous lens is extracted during cataract surgery and replaced by a synthetic IOL.

This is where the Acrysof monofocal lens implant comes in handy. Alcon developed this IOL as a transparent yellow IOL in order to filter the blue light that is found in both natural and artificial lights. On the other hand, you’re advised to have an in-depth discussion with your surgeon before choosing this IOL as some patients who had a blue light filtering IOL implanted in their eyes experienced some difficulty in seeing blue colour ranges in dim light conditions.

3. Baush & Lomb LI61AO monofocal lens implant: This IOL is manufactured by Baush & Lomb. Baush & Lomb promise their clients an aberration free IOL. This means “A better quality of vision than what could be achieved with a conventional lens and with an effect that would not be lost or diminished through decentration”, according to what has been told by Louis D Nichamin MD in the annual meeting of the American Society of Cataract and Refractive Surgeons. Patients can enjoy now a better quality of vision regardless of the degree of corneal aberration of the patient’s cornea, decentration, tilt, or variation in pupil size.

The Torics

These IOLs can correct both the main visual complaints of patients, whether nearsightedness or farsightedness in addition to correcting astigmatism or correct astigmatism alone if the patient has only astigmatism.

Toric IOls are not part of the standard cost covered by Medicare if you are under the umbrella of Medicare. Expect to pay an extra $1000 approximately, if you would like to have a toric IOL implanted in your eye during cataract surgery.

The most commonly used types from this genre are:

1. STAAR Toric IOL: The STAAR Toric IOL is manufactured by STAAR Surgical Company. STAAR Surgical Company promises its patients supreme quality and excellence owing to their “pedigree”, since the STAAR Toric IOL is the world’s first toric IOL for the reduction of astigmatism.

The STAAR Toric IOL gained FDA approval in November 1998, and it was the only toric IOL available on the US market until recently. The STAAR Toric IOL exhibits excellent rotational stability (The ability of the IOL to stay at exactly the same position as it was when first implanted without being rotated to left or right) through their newer TL model which was released in 1999. It is the only toric IOL made from silicon, and this ensures flexibility of the lens in addition to stability and safety to the eye. The silicon design ensures greater optical performance due to higher quality and fewer aberrations compared to acrylic lenses.

2. AcrySof Toric IOL: The Acrysof Toric IOL is manufactured by Alcon laboratories. It relays on a new technology called bioadhesive bonding to minimize or even eliminate the incidence of rotation of the IOL inside the lens capsule off the planned axis after implantation.

The bioadhesive technology allows for rapid adhesion between the IOL and the posterior capsule owing to the properties of the materials used in manufacturing the Acrysof Toric IOL. The IOL is made of a polymer that has ultraviolet and blue light filters thus enabling extra protection to the delicate retinal tissue. The IOL has a unique design that enables it to resist the formation of pco (posterior capsular opacity) after cataract surgery, thus minimizing the need for undergoing a subsequent YAG laser capsulotomy.

The presbyopia-correcting IOLs

These resemble the newest generation of IOLs having the ability to compensate for the loss of the accommodative power of the natural crystalline lens. Many technologies have been implemented in these high-end IOLs to allow the patient to see clearly for far (during walking) as well as for near (during reading). Thus minimizing or even eliminating the need for reading glasses after cataract surgery.

You are expected to pay an extra $2000 for a premium presbyopia-correcting IOL, supposing you have Medicare coverage for the basic costs of the cataract surgery.

The most commonly used types from this genre are:

1. AcrySof® IQ ReSTOR® IOL: The Acrysof ReSTOR IOL is manufactured by Alcon laboratories. It is considered the first multifocal IOL in the world. The idea behind this impressive IOL is a new technology called “Apodized diffraction zones” in which multiple blended diffraction zones allow the patient to see near, intermediate, and distant objects.

In a study performed on patients after having the ReSTOR iOL implanted in their eyes, 78% of the patients reported that they no longer needed to wear glasses. The IOL is made from soft foldable acrylic polymer allowing for easy implantation through a small incision that doesn’t need to be sutured, the thing that allows for speedy recovery after the operation in a comfortable manner to the patient.

2. ReZoom multifocal IOL: The ReZoom multifocal IOL is produced by Abbott Medical Optics. The ReZoom multifocal IOL gained the FDA approval in 2005. It has a unique optical design allowing light to be distributed on five optical zones thus enabling the patient to see near, intermediate and distant objects. In a study that was performed on patients receiving the ReZoom multifocal IOL, 92% of patients stated that they never needed to use glasses after the operation or used it rarely. The IOL is made from foldable high-refractive-index acrylic material allowing for easy implantation in the eye through a small incision thus enabling a rapid recovery after surgery.

3. Crystalens: The Crystalens is manufactured by Baush & Lomb. The Crystalens was first designed by Eyeonics Incorporation as the first accommodating IOL in the world. Eyeonics Incorporation gained FDA approval in November 2003. Baush & Lomb acquired the Crystalens in 2008, and introduced a new generation of the Crystalens called the Crystalens HD; it is still developing new generations of the Crystalens HD.

This impressive IOL has the main body of the IOL (the optic) attached to supportive flanges. Each flange has a hinge made from a special type of silicone named BioSil that was thoroughly tested to make sure that the hinge will have the ability to produce unlimited flexing movements in the eye. This allows the IOL to move forward and backward with the accommodative movement of the ciliary muscles of the eye thus mimicking the normal accommodation of the human crystalline lens. This gives the patient the ability to see clearly at near distance, intermediate distance, and distant objects, thus minimizing the need to wear glasses after cataract surgery.

Unfortunately, this revolutionary technology is pretty costly. Expect to be asked for an extra cost of around $3300 if you would like to have a Crystalens implanted in your eye after cataract surgery.

At the end of the day, you could say all IOLs are relatively costly – but some might consider it a small price to pay in return for the reduced dependency on glasses and greater quality of vision.

Facebooktwittergoogle_plustumblrFacebooktwittergoogle_plustumblr