A Complete Guide
An intraocular lens is implanted in the eye once your natural lens which has turned opaque due to the removal of cataract, to restore your vision to optimal. With advances in available technology for cataract surgery, the kind of intraocular lenses, called IOLs, have also undergone a revolutionary change. The first IOL that was implanted in the human eye, by Sir Harold Ridley in 1949, was made of acrylic called Perspex.
Intraocular lenses were approved as “safe and effective” in the USA by the Food and Drug Administration (USFDA) only in 1981. From then to now, the kinds of lenses that are available for implantation has been nothing short of a revolution for cataracts treatment.
Types of Intraocular Lenses (IOLs)
The two most common types of lenses are:
Anterior Chamber Lenses (ACIOL): These lenses are placed on top of the iris, the brown part of the eye. It is not the physiological position of the natural lens of the eye, and this type of lens is not the preferred IOL after non-complicated cataract surgery. ACIOLs are implanted in case the posterior capsule of the lens is deficient or damaged.
Posterior Chamber Lenses (PCIOL): These lenses are tucked into the place over the residual posterior capsule in the physiological position of the natural lens of the eye and are the preferred lenses.
The rest of this article will discuss the major types of advanced PCIOLs available for implantation after modern cataract surgery, namely, phacoemulsification, Microincision cataract surgery or Femtosecond laser cataract surgery. These lenses are collectively called premium IOLs.
Introducing Intraocular Lenses: What are the differences?
In modern cataract surgery, the clouded crystalline lens is removed and replaced by an artificial intraocular lens (IOL). Intraocular lenses represent a highly innovative technology – both in terms of corrective power and the quality of vision provided. Different types of intraocular lenses are available today, enabling good vision at one, two or all three distances:
Near: Approx. 40 cm (Reading).
Intermediate: Approx. 80 cm (Computer work).
Far: Beyond 100 cm (Spatial orientation).
Intraocular lenses enable good vision at all three distances
IOLs can simulate the refractive properties of the natural lens, however they do not have the ability to accommodate. Advanced intraocular lenses are designed to meet additional, individual patient’s vision requirements. Depending on the design, the advanced IOLs can offer further benefits, such as improved contrast perception.
Intraocular lenses are usually made of a soft, synthetic, and biocompatible material. A typical IOL measures approximately between 11 and 13 mm in diameter. The thickness of the lens can vary, depending on its refractive power. The corrective power of the lens is individually calculated and may differ for each eye. An IOL is transparent and neither visible nor perceptible in the eye.
Different Types of Intraocular Lenses
- Monofocal IOLs
- Bifocal IOLs
- EDoF Lenses
- Trifocal IOLs
- Aspheric and Toric IOL Functions
Different Types of Intraocular Lenses
There are different types of intraocular lenses available today. Generally, there is a distinction made between standard and advanced intraocular lenses, also known as premium intraocular lenses.
1.Monofocal IOLs - Clear vision at one distance
This is the most common type of intraocular lens used in cataract surgery..
Light cannot be focused from both distant and near objects at the same time, so it means that a monofocal lens can correct vision at one distance, providing good visual perception for either near, or far distance.
Most patients choosing this option want to be able to see at a distance, allowing them to perform activities such as driving and watching TV. They usually need to use glasses to help with near vision tasks, such as reading, cooking and working on the computer.
Choosing the Right Distance
While most surgeons implant the monofocal option with distant focus to correct far vision, it is also possible to choose a monofocal lens with near correction to enable good vision up close. For all other distances, the patient needs to wear glasses.
The decision about whether distant or near sight should be corrected depends on the patient’s lifestyle and visual needs. The decision should be made in agreement with the surgeon after a close consultation with the patient.
Standard types of monofocal IOLs have a spherical optic, which is equally rounded on both sides. It is normally paid for by your health insurance.
However, the natural crystalline lens of the eye has a slightly aspherical (not completely round) shape at the front, and is not equally curved on both sides. This shape enables it to precisely focus light rays entering the eye onto one point on the retina. The result is a clear, crisp image.
Advanced monofocal IOLs are available with an aspherical optic very similar to the original shape of the crystalline lens. The special design of the aspheric versions enable an enhanced image quality.
- IOL with aspheric surface
- Light rays focusing exactly onto one point on the retina
2. Multifocal Lenses: Bifocal IOLs - Clear vision at two distances
Bifocal intraocular lenses have two focal points, providing clear vision at two distances, far and near. Patients choose this option over a monofocal IOL when they wish to see clearly at additional distance, and become less dependent on visual aids. Bifocal IOLs allow you to see clearly and perform tasks such as reading and driving without glasses. However, you may still need to wear glasses for certain tasks in the intermediate-range (approx. 80 cm), such as computer work and cooking.
| Advantages of Bifocal IOL
- Less dependent on glasses for nearby activities such as reading and sewing
- Also activities requiring good far vision, such as driving
- With bifocal IOLs you will no longer need reading glasses.
| What you should know
If you suffer from certain eye diseases, such as glaucoma, diabetic retinopathy, diabetic macular oedema, or macular degeneration, you may not be eligible for bifocal introcular lens. Discuss alternative options with your ophthalmologist if you suffer from any of these diseases.
- Glare in certain low lighting situations
- Halos around light sources at night
- Decreased contrast sensitivity- slightly reduced contrast and a less sharp image on the retina. This is due to the lens splitting light from different distances. Therefore, patients have to compromise a little bit on the image quality to gain the multifocal effect.
- Visual disturbances at night
3. EDoF LensesClear vision at intermediate and far distances
EDoF (Extended Depth of Focus) intraocular lenses use an advanced optical technology that allows to increase the range of focus compared to standard monofocal types.EDoF IOLs work by bending the light entering the eye from intermediate and far distances and focusing this light onto a single focal point on your retina.
Extended Depth of Focus (EDoF) lenses provide sharp vision over a wide range, allowing you to see objects clearly at different distances from far to intermediate: approximately at arm’s length.Thus,enable you to perform a broad spectrum of activities without glasses, including: sports, socializing, working on the computer, driving a car, watching TV, cleaning, cooking, shopping, other typical home and garden tasks.
| Advantages of EDoF IOLs
- Perfect balance between increased freedom from glasses and reduced visual side effects associated with the multifocal types.
- Less sensitive to these light phenomena, so less halos or glare around light sources,
- enjoy good night vision
- The undisturbed and reliable visual performance gives patients a feeling of added comfort and safety.
| What you should know
EDoF lenses offer a high degree of spectacle independence. However, the achieved vision quality is very individual and may differ from patient to patient.
4. Multifocal Lenses: Trifocal IOLs
Clear vision at all distances
These are the most advanced intraocular lenses (IOLs) available today, providing clear vision for near, intermediate and far distances. They are designed to enable a high degree of independence from glasses for patients leading an active life and wishing to do without visual aids.
How Trifocal Lenses Work
Trifocal lenses work by bending the light entering the eye from near, intermediate and far distances, and focusing this light onto a single focal point on your retina.
Trifocal Lenses in Daily Life
Unlike monofocal and bifocal options, trifocal lenses also provide comfortable intermediate vision, which is important for various daily activities, such as computer work.
It allows you to perform a range of activities in everyday life without glasses. This includes daily tasks such as: reading, cooking, cleaning, ironing, working on the computer, shopping, watching TV, driving, working in the garden
| Advantages of Trifocal Lenses
The biggest advantage of trifocal IOLs is the possibility to see clearly at all distances without glasses
You may no longer need to wear glasses when pursuing your daily activities.
Allow for the treatment of pre-existing vision disorders, such as myopia or hyperopia.
| What you should know
If you suffer from eye diseases, such as glaucoma, diabetic retinopathy, diabetic macular oedema, or macular degeneration, you may not be a suitable candidate for trifocal lenses. ophthalmologist.
Higher degree of visual disturbances and light phenomena (dysphotopsia)
Glare in certain low lighting situations
Halos around light sources at night
Decreased contrast sensitivity
less image quality.
5.Toric and Aspheric IOL
Toric intraocular lenses enable the treatment of astigmatism, a common vision disorder affecting roughly one third of the global population and causing distorted vision.
Both aspheric and toric IOLs have special characteristics to enable clear, crisp images.
Which is the best IOL for you?
Which is the best IOL for you?
In medicine, like life, there is no single best answer. Your doctor will discuss with you the potential benefits of each of these lenses, and help you select the one best suited for your lifestyle and visual needs, as well as your expectations from the cataract surgery. Lifestyle and priorities: In case you have a very active lifestyle that involves a lot of precise focusing outdoors, like golf, you may compromise your near vision but not your distance vision. If you travel a lot, you might prefer to not be dependent on glasses at all, preceding a bit of precision for both near and distance vision. On the other hand, if you enjoy sewing or embroidery, you will want perfect near vision.
Pre-existing diseases: In case of certain eye diseases like advanced glaucoma, corneal disorders or age-related macular degeneration, you may not be a good candidate for specific lenses, like the multifocal lens. Your eye doctor will perform a comprehensive eye exam and discuss its results and implications with you, to help you choose the best possible lens for your eye.
Costs: These lenses are more expensive than traditional IOLs, adding an incremental value to the cost of cataract surgery. The premium lenses come at a price that is usually not covered by insurance companies.
The doctors at Indovision Cataract & Laser Eye Centre are well versed in the use of premium IOLs following cataract surgery in Pune. Your eye doctor will be happy to discuss all the options available and help you choose the best choice for your eye health, and visual needs.