Lens Implantation

Overview

An intraocular lens (IOL) is a lens that is implanted in the eye to treat cataracts or myopia. If the natural lens is retained, the IOL is referred to as phakic; otherwise, it is referred to as a pseudophakic, or false lens. After the eye's hazy natural lens (colloquially known as a "cataract") has been removed, such a lens is commonly implanted during cataract surgery. The pseudophakic IOL performs the same function as the natural crystalline lens in terms of light focusing. The phakic type of IOL is used in refractive surgery to modify the optical power of the eye as a therapy for myopia. It is put over the existing natural lens (nearsightedness). 

IOLs are typically made up of a tiny plastic lens with plastic side struts called haptics that keep the lens in place inside the eye's capsular bag. IOLs were previously made of an inflexible material (PMMA), however this has been mainly replaced by the use of flexible materials such as silicone.

The majority of IOLs used today are fixed monofocal lenses designed for distance vision. Other types of intraocular lenses are available, such as multifocal intraocular lenses, which give multiple-focused vision at distant and reading distances, and adaptive intraocular lenses, which provide limited visual accommodation. Multifocal IOLs can also be Trifocal IOLs or have an extended depth of focus (EDOF) lens.

Every year, around six million lenses are implanted. The surgery can be performed under local or topical anaesthetic, with the patient awake throughout. The use of a flexible intraocular lens allows the lens to be rolled for insertion into the capsular bag through a very tiny incision, eliminating the need for stitches. In the hands of a skilled ophthalmologist, this procedure usually takes less than 30 minutes, and the recovery time is around 2–3 weeks.

Patients should avoid excessive activity or anything else that significantly raises blood pressure after surgery. They should see their ophthalmologists for three weeks to ensure that the implants are working well.

Infection, loosening of the lens, lens rotation, inflammation, and evening halos are all concerns linked with IOL implantation, however a comprehensive analysis of research found that the process is safer than standard laser eye therapy. Despite the fact that IOLs allow many patients to minimize their reliance on glasses, the majority of patients still use glasses for some tasks, such as reading. If Multifocal IOLs, Trifocal IOLs, or EDOF lenses are used, these reading glasses may be ignored.

What are Intraocular Lens Implants?

An intraocular lens (IOL) implant is an acrylic alternative for your natural lens in your eye that takes over the image-focusing function. Like the natural lens, the IOL concentrates light within the eye.

IOLs can correct a broader spectrum of visual issues than any other type of vision correction surgery. They are capable of correcting myopia, hyperopia, astigmatism, and presbyopia (the difficulty focusing up close that starts around age 40). An IOL, on the other hand, is most typically used to correct eyesight as part of cataract surgery or Refractive Lens Exchange.

An IOL is around one-third the size of a dime. It is round in the center and has "haptics" arms on either side that keep it in place. 

Material used in manufacturing intraocular lens (IOL)

Polymethylmethacrylate (PMMA), silicone, hydrophobic acrylate, hydrophilic acrylate, and collamer have all been utilized to make intraocular lens implants. PMMA (polymethylmethacrylate) was the first material to be effectively employed in intraocular lenses. 

Sir Harold Ridley, a British ophthalmologist, noticed that Royal Air Force pilots who had eye injuries from PMMA windshield material during World War II showed no rejection or foreign body reaction. Ridley constructed and placed the first intraocular lens in a human eye after determining that the transparent material was inert and suitable for implantation in the eye.

Technology advancements have resulted in the utilization of silicone and acrylic glass, both of which are soft foldable inert materials. As a result, the lens may be folded and placed into the eye through a smaller incision. Acrylic lenses are a better choice for people who have a history of uveitis or who are likely to need retinal surgery requiring vitrectomy with silicone oil replacement, such as people with proliferative diabetic retinopathy, or who are at high risk of retinal detachment, such as people with high myopia.

According to one study, eyes treated with hydrophobic acrylic IOLs were more than twice as likely as eyes treated with silicone IOLs to achieve best corrected visual acuity of 20/40 or above in individuals with a history of uveitis.

How Do IOL Implants Work?

Each eye has a lens (a window made of clear protein and water that sits behind the pupil). The lens focuses light onto the retina, which sends it to your brain.

The IOL is a lens that replaces the normal lens of the eye. The lens is initially removed via a technique known as phacoemulsification. A small incision is created on the cornea's margin. The lens is then shattered into little fragments and washed out of the eye. The IOL is folded and put via the tiny incision, resting in the same transparent capsule as the natural lens formerly did.

When selecting the ideal power for the IOL, the length of the eye, the curvature of the cornea, and the location of the lens within the eye are all taken into account. To fine-tune this measurement, extensive measurements are done both before and during operation.

As we age, the clear proteins within the natural lens of your eye may change and turn parts of your lens cloudy. This condition is known as a cataract, which can blur and impair your vision and worsen over time. Cataracts are incredibly common and are a leading cause of blindness especially in older demographics. It is estimated that more than half of all people will either have a cataract or will have had cataract surgery by the time they reach 80 years of age.

During cataract surgery, the intraocular lens implant is commonly used. Intraocular lenses function similarly to natural lenses. As light rays approach the eye, the IOL bends (or refracts) them to help you see clearly. A lens implant, like prescription contact lenses or spectacles, can have different focusing capabilities.

Types of Intraocular Lens Implants

1. Monofocal:

Monofocal intraocular lenses (IOLs) are common lenses used in cataract surgery. One of the greatest disadvantages of conventional IOLs is that they can only be focused for a single distance - either optical infinity (making the eye emmetropic) or a fixed limited distance (rendering the eye myopic). Patients who have a typical IOL implant no longer have clouding from cataracts, yet they are unable to accommodate (change focus from near to far, far to near, and to distances in between).

Most cataract procedures are performed on older persons who are already fully presbyopic, therefore this is not an issue. It can, however, be a concern for individuals who are not yet presbyopic (or are in the early stages of presbyopia) and are having refractive lens exchange to address refractive defects. Monovision, in which one eye is made emmetropic while the other is made myopic, can partially compensate for the lack of accommodation and allow for clear vision at varied distances.

With the approval of the Food and Drug Administration, more adaptable types of lenses (multifocal and accommodating IOLs) were released in the United States in 2003. These come at a cost to the receiver that is in addition to what Medicare will pay, and each has advantages and disadvantages.

2. Multifocal:

Multifocal IOLs attempt to provide distant and near vision viewing at the same time. Trifocal intraocular lenses (IOLs) can give intermediate vision. Many multifocal IOL designs aim to accomplish this simultaneous viewing focus through the use of a concentric ring design that alternates between distance and near focal points. Many concentric ring multifocal lenses used today, on the other hand, are prone to glare and have somewhat degraded focus at all ranges of vision.

People who have a multifocal IOL after having their cataract removed may use fewer glasses than those who have regular monofocal lenses. People who receive multifocal lenses, on the other hand, may face greater visual issues than those who receive monofocal lenses. Glare, halos (rings around lights), and a lack of contrast sensitivity in low-light conditions are the most prevalent adverse visual consequences of multifocal IOLs.

3. Accommodating:

Some recent lens designs seek to restore some partial focusing power to the eye in order to adjust focus from distant to near (accommodation). However, many accommodating IOLs used now only provide a marginal improvement in near vision, which diminishes with time.

Although there is some uncertainty around this finding, accommodative intraocular lenses may have a slightly greater risk of developing posterior capsule opacification (PCO).PCO is a frequent side effect of many cataract procedures, and it is readily treated with a single laser capsulotomy procedure.

Accommodating IOLs engage with ciliary muscles and zonules, employing hinges at both ends to "latch on" and move forward and backward inside the eye in the same way as regular accommodation does. These IOLs include a 4.5-mm square-edged optic and a lengthy hinged plate design with polyimide loops at the haptics' ends. The hinges are comprised of an advanced silicone called BioSil, which was rigorously researched to ensure that it could flex in the eye permanently.

4. Toric:

A toric intraocular lens (IOL) is a form of toric lens that is used during cataract surgery to correct preexisting corneal astigmatism. Astigmatism can also be treated with limbal relaxing incisions or by using an excimer laser. Around 40% of Americans have considerable astigmatism and may be good candidates for a toric IOL. Cataract surgery with a toric IOL is fundamentally identical to cataract surgery with a standard IOL.

Toric IOLs, like toric contact lenses, have differing powers in different meridians of the lens and must be positioned on the right meridian to reverse preexisting astigmatism. If the toric IOL is not positioned correctly, it may need to be repositioned in a subsequent surgery.

5. Multifocal toric:

Standard toric IOLs are monofocal, permanently focused on distant objects. Multifocal toric IOLs are also available. These lenses provide the patient not only with correction of preexisting astigmatism, but also with multiple-focused vision at far and reading distance

What happens during surgery?

You'll see an ophthalmologist if you have a cataract. This doctor is an expert in eye surgery and problems. They'll probably advise you that it's better to wait until the cataract starts to interfere with your everyday life before having it removed. The operation can be performed in a hospital or an outpatient clinic.

To get you ready, your doctor will:

• Measure your eye. This will help them pick the right implant for you.
• Give you medicated eye drops to take for a few days ahead of time.
• Ask you to stop taking some medicines or to skip wearing contact lenses for several days beforehand.

On the day of surgery, they'll:

• Numb your eye.
• Give you a drug to help you relax. You may see light during the procedure, but you should feel nothing or only a gentle pressure.
• Make a tiny cut through your cornea to get to the lens.
• Break the lens up into pieces and remove it bit by bit.
• Put the implant in place.
• Let the cut heal by itself - no stitches.
• You can usually go home in less than an hour, but you'll need someone else to drive.

How Long Do IOL Implants Last?

IOL implants are constructed of materials that do not degenerate over the period of a person's life, thus they do not need to be replaced. However, because the procedure is reversible, implants can be exchanged if you do not see an improvement in your vision.

Are Lens Implants Safe?

While there are risks involved with any type eye surgery, problems following an intraocular lens implant procedure are uncommon. Your ophthalmologist will thoroughly examine your eyes and review your medical history before to any surgery to decide if you are a good candidate for an IOL operation. This will assist in determining whether there are any risk factors for IOLs that you should be aware of.

This operation may cause minor bleeding, redness, and irritation, all of which will pass shortly. A detached retina, infection, or severe inflammation, which might result in visual loss, are among the more significant dangers of surgery. Following surgery, your doctor will advise you to use medicinal drops. It is critical to take these drops exactly as directed to avoid infection or irritation.

What is the recovery time for an IOL implant procedure?

It is also possible for the implant to move out of position which would necessitate a follow-up procedure to correct the intraocular lens’ alignment in your eye.

The vision is often blurry immediately following the surgery and then clears up over the next few days. It is recommended to avoid heavy lifting or straining for the first 2 weeks following the surgery.

What should I do after surgery?

It'll take about 8 to 12 weeks to fully heal. During that time:

• Keep your eye protected with sunglasses as much as possible, and sleep with your eye shield at night.
• Don't rub or press your eye, even if it's itchy or oozes a bit of fluid.
• Take the medicated eye drops your doctor prescribes. You'll use them for several weeks to help your eye heal.
• Avoid most exercise or heavy lifting. The doctor will tell you when you can do those things again.

Conclusion

An intraocular lens (or IOL) is a small, artificial lens that is implanted in the eye. It replaces the natural lens of the eye, which is removed during cataract surgery.

Light rays entering the eye are twisted (refracted) by the lens, allowing you to see. Your lens should be crystal clear. However, if you have a cataract, your lens is clouded. With a cataract, things appear blurry, foggy, or less colorful. Cataract surgery replaces the clouded lens with a clear intraocular lens (IOL) to enhance your vision.

IOLs, like prescription eyeglasses or contact lenses, come in a variety of focusing capabilities. The length of your eye and the curvature of your cornea will be measured by your ophthalmologist. These measures are used to determine the focusing power of your IOLs.

The majority of IOLs are made of silicone, acrylic, or other plastic materials. They're also coated with a unique substance that shields your eyes from the sun's damaging ultraviolet (UV) rays. An intraocular lens implant, or IOL, is a transparent plastic device roughly the size of a dime. There are lots of types:

Monofocal IOL: This is the most common. Unlike your natural lens, which can stretch or bend to help your eye focus, this implant stays focused at one fixed distance. If yours focuses at a distance, you might be able to see things far away but need glasses to read or see close up.

Multifocal implant: Like glasses with bifocal or progressive lenses, this lens has areas that help you see things at different distances. It could take several months for your brain to adapt so your vision seems natural. It can sometimes cause more halos or glare around lights than a monofocal lens. 

Accommodating IOL: This flexible option acts more like your natural lens and focuses at more than one distance. It makes you less likely to need reading glasses.

Toric IOL: You'll get this if you have astigmatism, or a cornea that's more football-shaped than round. This can make vision blurry all over, not just close up or far away. This lens lessens astigmatism so you won't need glasses to correct it after your surgery.

Any surgery has a chance of complications. It's rare after an intraocular lens implant, but you might notice bleeding or get an infection. Redness or swelling are more common. More serious risks include: A detached retina, which happens when that layer of nerve cells separates from the back of your eye. This is a medical emergency, Vision loss, Dislocation (when the implant moves out of position).