Understanding the Types of INTRA OCULAR LENS IMPLANTS (IOL) for Cataract Surgery

 An intraocular lens (IOL) implant is a tiny, synthetic lens made of plastic, silicone, or acrylic that is used to replace the cataractous lens. Since this lens is placed in about the same place in which the cloudy natural lens had been, the restored vision is more natural than any other older method of Cataract treatment. The IOL implanted is designed to last indefinitely. Side vision and image size are normal and there is no discomfort. There is also no foreign body to irritate the surface of the eye. This is currently the most commonly-used option.

Nowadays we have a wide array of lenses to choose from. The choice of lens could depend upon the patient’s budget, requirement, life-style and the desire to see the very best possible. The artificial lens chosen especially for your eye will give you clear vision for the rest of your life. Your eye surgeon will advise you on the most suitable lenses available and you will have a choice; for example you may opt for a lens that gives you clear vision in the distance and near (reading), called a multi-focal lens, which could mean minimal or no dependence on specs – for life!

Types of IOLs

The most common type of IOL is called a posterior chamber lens, meaning it is placed behind the iris within the capsule. When it is placed in front of the iris, as might happen when the lens capsule is damaged, it is called an anterior chamber lens.

Here we focus on the most common type of IOL and the different lenses that have evolved from this technique. All of the forth coming discussion of IOL is of posterior chamber IOL. 

There are two types of IOL available; non-foldable and foldable.

Non-foldable Lenses (IOL): – 

Are made of a hard-plastic material (PMMA), are bigger in size & bigger incisions need to be made to insert them. These are the basic and the most initial IOL developed. As these IOLs cannot be folded so an incision (cut) as big as the IOL is mandatory for implantation in the eye. Technologically these are most basic of lenses and so could only be monofocal.

Limitations of Non – Foldable IOL: 

Most of the limitations arise due to the necessity of putting a larger incision to implant this type of IOL. With non-foldable IOL, the surgical incision has to be at least as big as the IOL, which is 5.5-6.0 mm – 

• The healing time is prolonged.
• The chances of infection become higher.
• The chances of induced astigmatism become higher with bigger incision.

The non-foldable IOL are overall less in diameter than foldable IOL so the chances of glare increase because of smaller IOL.

• Foldable Lenses (IOL): – 

The next step in technological advancement is the development of foldable lenses. These are made of a soft acrylic material which can be folded or rolled so as to be injected through a very small incision into the eye. Once inserted at the right place, the IOL unfolds and stabilizes in the eye to give a lifetime of clear vision.

Advantages of Foldable IOL

Foldable Lenses (IOL) could be either MONOFOCAL or MULTIFOCAL.

1. Foldable IOL is made up of soft Acrylic material which is more bio-compatible.
2. Needs very small incision for insertion in the eye. Usually the incision size is 2.8 mm or less.
3. The chances of induced astigmatism become much less due to much smaller incision.
4. Very short healing time up to 4-5 days only. 
5. Chances of infection are minimal.

Monofocal Lenses (IOL): These IOLs provide a set focal point and can fix your vision for one distance only.  The implant cannot change shape like your original natural lens. As the monofocal IOL will have the capacity to either focus in distance or on near objects, the patient has to decide which part of his vision he wishes to attain without depending upon glasses. As most of our visual needs are for distance, majority of the patients go in for distance vision. In such cases, the patient is dependent on progressive bifocals for near vision. If you have astigmatism and you elect for a monofocal lens implant, then you should expect to need glasses to achieve the best clarity for all distances of vision. If you have your astigmatism corrected at the time of surgery (such as with Laser Cataract Surgery or by choosing a Toric IOL), then you can expect relatively good distance vision but to rely on reading glasses for most near activities.

Multifocal IOLs: These IOLs have revolutionized existing state-of-the-art cataract surgery. Multifocal IOL helps to achieve the ultimate goal of INDEPENDENCE from glasses. These advanced technology IOLs are a newer type of lens that has multiple focal points and reduces or eliminates the need for eyeglasses or contact lenses after cataract surgery. As part of the rapid evolution in IOL innovations, these newer lenses are made from cutting-edge materials with unique features. This is made possible through highly specialized optics that divide light and focus it on more than one point to provide a range from near to far eyesight. 80% of patients who get these lenses will never need glasses for any activity. Of those 20% of patients who need glasses for certain activities, do so for very fine near work done for prolonged period of time. More over the near glasses needed are of much less power than those needed by patients with monofocal IOL.

Advanced Technology IOLs – Lifestyle Lens

1. Premium Monofocal IOL
2. Multifocal (Bi-Focal) and Tri-Focal IOL
3. Astigmatism Correcting Toric IOL

Premium Monofocal IOL:

As the technology has advanced so has the type of lenses available advanced. The basic monofocal IOL which has been there for a long time does not address many other problems related with vision. The vision restored after cataract surgery needs to be qualitatively as well as quantitatively excellent. Gone are the days when ‘just seeing’ after cataract surgery was deemed sufficient. The wide range of premium IOL available today make sure that your vision is restored to a level equal to better than what you had before developing cataract.

 The problems associated with low quality basic IOLs are:

1. Material of lens: The most basic of material used to make IOL is PMMA which is a type hard plastic. Although this is rarely used in developed countries, it is still quite frequently used in our country to cut down the costs.
2. Manufacturing process: The quality control exercised during manufacturing will decide whether the IOL is free of internal defects as well the predicted power of the IOL is accurate or not.
3. Design of the IOL: The basic IOL is spherical in shape which will give rise to distorted shape at the edges. Our natural lens which gets replaced during cataract surgery is aspherical in shape which means that the lens is curved in the centre and flat at the edges.  
4. Aberration in the IOL: The lower the quality of IOL material and manufacturing process, the more are the chances of introducing aberrations in the visual pathway. Aberrations are very small defects which though may not be apparent to naked eye but will cause a marked deterioration in quality of vision.
5. No protection from UV rays

The more advanced IOLs that we have today, have addressed most of these problems as well as added many other features which have not only significantly improved the quality and quantity of vision but has also accorded several new benefits to the patients. The advanced features that we find in the premium IOLs are:

1. Quality of IOL: The premium IOL are made from acrylic which is a much softer and better grade plastic than PMMA
2. Quality Control: The strict quality control during manufacturing process of premium IOL ensures the correct power and design specifications.
3. Aberration Free IOL
4. UV light filters
5. Blue light filter for rich vibrant colours
6. Maintains Contrast Sensitivity
7. Enhances depth perception
8. Corrects higher order spherical aberration of the eye
9. Natural yellow tinted IOL to protect better from UV Rays and to provide better colour clarity.

Multifocal (Bi-Focal and Tri-Focal) IOLs have two or three focal points and restore vision at more than one distance, giving the patient a chance of being more independent of glasses. Multifocal lenses include bifocal and trifocal IOLs, with the latter representing the most advanced technology. Trifocal IOLs allow the highest level of independence from glasses, enabling patients to see clearly at all three distances without them.

• Astigmatism Correcting Toric IOLs are usually not multifocal in nature but are designed to correct a wide range of astigmatism. If you have astigmatism, then this lens may help to reduce your need for glasses for distance vision but it will not eliminate the need for some eyeglass use. The most advancement IOL in this category is now also available as multifocal toric IOL. However these are mostly under trial at many centres and it will be sometime before they are used routinely. 

At AELC, we have access to and are well trained and experienced in using all the latest intraocular lenses (IOL) available today, and considering this lens will remain in your eye for the rest of your life, we have a selection of only the finest at our centre, including:

UNI-FOCAL INTRA OCULAR LENS

1. Rayner RayOne RA0 100C
2. Hanita IOL
3. Rayner RayOne RA0 600C
4. Bausch and Lomb Akreos AO IOL
5. Alcon Acrysof Multi-Piece IOL
6. Alcon Acrysof Single-Piece IOL
7. Alcon Acrysof IQ IOL
8. Bausch and Lomb Envista IOL
9. Alcon Acrysof IQ Toric IOL

 MULTIFOCAL (BI-FOCAL and TRI-FOCAL) INTRA OCULAR LENS

1. Zeiss AT Lisa 809 Multi-focal (Bi-focal) IOL
2. Zeiss AT Lisa 909 Multi-focal (Bi-focal) Toric IOL
3. Zeiss AT Lisa Tri-focal IOL
4. Zeiss AT Lisa Tri-focal Toric IOL
5. Alcon Acrysof ReSTOR Multi-focal (Bi-focal) IOL
6. Alcon Acrysof ReSTOR Multi-focal (Bi-focal) Toric IOL
7. Alcon Acrysof IQ PanOptix Tri-focal IOL
8. Alcon Acrysof IQ PanOptix Tri-focal Toric IOL

Decision Making in Life-Style IOL:

If you would like to have greater independence from eyeglasses or contacts, then a multifocal or accommodating lens implant may be right for you. Referred to as Lifestyle Lenses, these lens implants offer a wider range of vision than monofocal lens implants. Available Lifestyle Lenses include Tecnis Multifocal, ReSTOR, Crystalens, and ReZoom IOL options. Each of these has its own advantages and should be considered along with your unique visual needs, work, and hobbies.

While everyone may be a potential candidate for these advanced technology IOLs, certain criteria allow for the best possible outcomes with any of these lenses:

If you would like to have greater independence from eyeglasses or contacts, then a multifocal or accommodating lens implant may be right for you. Referred to as Lifestyle Lenses, these lens implants offer a wider range of vision than monofocal lens implants. Available Lifestyle Lenses include Tecnis Multifocal, ReSTOR, Crystalens, and ReZoom IOL options. Each of these has its own advantages and should be considered along with your unique visual needs, work, and hobbies.

While everyone may be a potential candidate for these advanced technology IOLs, certain criteria allow for the best possible outcomes with any of these lenses:

While some of these conditions listed might make you a poor candidate for one type of Lifestyle Lens, you may still be a candidate for another type of Lifestyle Lens. It is important for you to be able to review the unique features of your eyes with your doctor to determine what may be the best option for you.

These lens implants are designed to provide a dual focus with part of the lens set for distance and part set for near. The design is different from bifocal eyeglasses where the distance of focus depends on your direction of gaze (looking through the top portion for distance focus and the bottom portion for near focus). With a multifocal lens, the brain learns to automatically find the correct focus.

Not everyone with a multifocal lens implant can read equally well without glasses. Many different factors can cause this individual variability. The ability to read without glasses tends to be better if both eyes have a multifocal lens. The younger and healthier that the eye is, the better the reading ability will be. The ability to read without glasses seems to improve over time for most patients. This is believed to be due to the brains tendency to learn to perform better with practice with the multifocal lens system. While there is no guarantee that you will read as well without glasses as you desire, multifocal lenses give you much better odds of doing so, compared to monofocal lens implants.

Monovision

Monovision refers to the option of choosing to have one eye corrected for distance vision and the other eye correct for intermediate or near vision. If you are a candidate for and choose to have monovision, you may occasionally need glasses for distance or near tasks but may go without glasses much of the time.

Different Types of Cataract Surgery with Different Types of Intra-Ocular Lens (IOL)