Types And Evolution Of IOLs

In order to fully understand the technological evolution of cataract surgery over the past 50 years, we need to compare current surgical procedures and visual recovery times with those reported half a century ago.

A look at the history of cataract surgery clearly shows that its evolution is an outcome of the vision of a few inspired pioneers who had great passion for their profession. When phacoemulsification was first developed, it faced strong opposition and hence took time in being accepted by the majority of eye surgeons.

It was only with the introduction of intraocular lenses (IOLs), and to a greater degree with the advent of foldable IOLs, that the technique was accepted and used on a much larger scale. In the same way, the evolution of the IOL itself was influenced by ongoing technological progress with phacoemulsification devices and phacoemulsification techniques.

This progress led to the development of lenses that could be inserted through increasingly smaller incisions. Today we are able to perform cataract surgery in a few minutes, with visual rehabilitation, and we owe it exclusively to a small number of surgeons who firmly believed in these technological innovations.

Even though cataract surgery has been practiced for over 2000 years, modern cataract surgery started just some 50 years ago with the first IOL implantation by Sir Harold Ridley. The development of intraocular lenses was accompanied by great successes and disasters.

With the fast development of cataract surgical techniques over the past 20 years, a successful marriage between IOL-developments and surgery was established. Indication profiles for cataract surgery and IOL implantation extended to more and more patient groups.

At this time classical cataract surgery is further developing into refractive intraocular lens surgery to correct higher ametropia in clear lens or phakic eyes. This development was only possible because of the improvements of surgical techniques and implants in classical cataract surgery.

Intraocular lenses (IOLs) have come a long way from the first rigid polymethyl methacrylate, or PMMA, lenses implanted in the 1950s. Cataract surgery is now precise and predictable enough to allow surgeons to optimize refractive outcomes by offering a range of IOL technologies to satisfy patient needs.

Monofocal IOLs

Monofocal IOLs provide spherical correction for a single distance. These lenses do not address astigmatism or presbyopia – in other words, patients will require glasses for optimal vision after surgery.

Patients can choose distance, intermediate, or near with these lenses but cannot have multiple distance in focus at once (unless they choose monovision). Monofocal IOLs provide excellent image clarity and contrast with minimal aberrations, such as glare and halos.

These lenses are ideal for patients with ocular comorbidities, such as VF and contrast loss due to age-related macular degeneration (AMD) or glaucoma. Many lenses are variations of the common monofocal IOL platforms offered by the major IOL manufacturers.

Most current monofocal IOLs implanted, such as the Johnson & Johnson Vision (J&J) Tecnis (ZCB00), Alcon Acrysof (SA60WF), Vsy Biotech GmBH Enova™, and Bausch + Lomb enVista (MX60E), are one-piece lenses made of hydrophobic acrylic.

These lenses are foldable and are designed for placement in the capsular bag. J&J’s recently approved monofocal, Eyhance (ICB00), with a modified anterior surface sphericity to increase depth of focus and provide some range of vision, is an added benefit to current monofocal options.

Many monofocal three-piece IOLs are available, including the J&J Tecnis (ZA9003), Zeiss CT-Lucia, and the Alcon MA60AC. These lenses consist of a central optic with separate haptics attached to opposite sides.

Advantages of three-piece lenses include the versatility to safely place them in the capsular bag, sulcus, or sclera via fixation. Monofocal IOLs are covered by health insurance in the United States, but all other lenses discussed are typically an extra cost to the patient.

Multifocal & Trifocal IOLs

Multifocal IOLs, as the name suggests, create multiple focal points at different distances to treat presbyopia. These lenses have a pattern of rings formed in the central optic.

The rings focus light to provide clear distance, near, and/or intermediate vision, depending on the lens. The most common multifocal IOLs are the J&J Tecnis and the Alcon ReStor.

These are effectively bifocal lenses, providing good distance and near vision with limited intermediate vision. They are generally available in different add powers as well as sphere and cylinder powers.

The newest multifocal IOL available in the United States is the Alcon PanOptix. This trifocal lens provides good distance, intermediate, and near vision. Other IOLs in this category are in the pipeline for FDA approval with enhanced options to optimize range and minimize halos and glare.

Multifocal IOLs have increased aberrations (halos and glare) due to the rings of the optic and are not advisable for patients who have retinal disease, glaucoma, or irregular corneas.

Toric IOLs

Monofocal toric IOLs are very similar to standard monofocal IOLs but also correct corneal astigmatism. These lenses must be positioned precisely during surgery based on preoperative measurements.

They are available in a range of sphere and cylinder powers to address most patients’ needs. All current monofocal, multifocal, and extended depth of focus (EDOF) platforms also are available in toric version for use in astigmatism treatment.

EDOF IOLs

EDOF IOLs treat presbyopia by extending the range of focus rather than splitting light into discrete focal points. The advantages of EDOF lenses are reduced aberrations compared to multifocal/trifocal IOLS and improved intermediate vision compared to multifocal IOLs.

Near vision with EDOF IOLs is typically not as high quality as with multifocal or trifocal IOLs. These lenses should also be considered only for patients with otherwise relatively healthy eyes. EDOF IOLs available in the United States are the J&J Tecnis Symfony and the recently approved Alcon Vivity.

Vivity is similar to a monofocal IOL with a slight central change in curvature, providing good intermediate and distance vision with low aberrations similar to a monofocal IOL.

Light Adjustable IOL

The Light Adjustable Lens (RxSight) is different from prior IOLs, as the power of the lens can be changed after implantation.

The lens optic contains monomers that can be activated by a UV light treatment to alter the shape and power of the lens. This lens is implanted similarly to the other lenses discussed.

In the postoperative period, the refraction is obtained and treatments are applied to the lens in-office, eventually locking in the final power around one month after surgery. This lens is ideal for patients whose preoperative calculations are challenging, such as those who have corneal irregularities or have had previous laser vision correction.

Light adjustable lenses do not address presbyopia and have high image quality with minimal aberrations comparable to monofocal IOLs.

Accommodating IOLs

Accommodating IOLs are designed to address presbyopia by changing position, shape, or configuration when the eye accommodates.

This recreates the natural change in lens power with accommodation, reducing or eliminating presbyopia; patients with these lenses can see well at distance, intermediate, and near. Unlike multifocal and EDOF lenses, which have aberrations due to the rings etched in the optics, accommodating IOLs have minimal aberrations as their optics are smooth.

These lenses can therefore be used in patients with ocular conditions such as glaucoma or AMD. The only currently available accommodating IOL in the U.S. is the Bausch + Lomb Crystalens, which features flexible haptics that allow some movement of the optic during accommodation to effectively change power.

This IOL depends on capsular flexibility to accomplish range of vision, and the degree of IOL flexibility varies from case to case. Other accommodating IOLs that change shape include the Alcon FluidVision, the Atia Vision, and the Juvene IOLs, which are in the pipeline for approval.

Most of these IOLs can also treat astigmatism with a toric version, and the modular lenses can also be designed for drug delivery.

Presbyopia-Correcting IOLs

Presbyopia-correcting intraocular lenses (IOLs) are an innovative type of artificial lens designed to address the vision changes associated with presbyopia, a common condition affecting people over 40. Unlike traditional IOLs that offer only one fixed focus, these specialized lenses can provide clear vision at varying distances, including close-up, intermediate, and far distances.

Presbyopia-correcting IOLs incorporate multiple focal zones within the lens, enabling the eye to adjust automatically to different distances. This means that people with these lenses implanted can enjoy clear vision at all distances, eliminating the need for reading glasses or other corrective lenses.

Presbyopia-correcting IOLs are an excellent option for people who want to reduce or eliminate their dependence on corrective lenses. They can significantly improve quality of life, especially for those who are highly active and engaged in work and hobbies that require good near and far vision.

Aspheric IOLs

Unlike traditional spherical IOLs, which are uniform in shape and curve, aspheric IOLs are designed with a gradual change in curvature that more closely mimics the natural shape of the eye.

The purpose of an aspheric IOL is to improve the quality of vision by reducing the aberrations and distortions that can occur with traditional spherical IOLs. By more closely mimicking the natural shape of the eye, aspheric IOLs can provide sharper and clearer vision with less glare, halos, and other visual disturbances.

Aspheric IOLs are particularly beneficial for patients with larger pupils or those who require a higher degree of visual acuity, such as those with certain occupations or hobbies that require good vision.

Monochromatic IOLs

Monochromatic intraocular lenses (IOLs) are a specialized type of artificial lens used during cataract surgery or to correct refractive errors in the eye. Unlike traditional IOLs, which are designed to provide clear vision across a broad range of wavelengths of light, monochromatic IOLs are designed to optimize visual acuity at a specific wavelength or color of light.

The purpose of a monochromatic IOL is to enhance contrast sensitivity and improve visual acuity, especially in low-light conditions. These lenses are particularly beneficial for patients with certain eye conditions, such as macular degeneration, that can affect visual function and contrast sensitivity.

Monochromatic IOLs are available in a range of wavelengths, from blue to green to red. The choice of lens will depend on the patient's individual needs and the nature of their eye condition.

Hydrophobic Acrylic & Hydrophilic IOLs

Hydrophobic acrylic and hydrophilic IOLs are two types of intraocular lenses used in cataract surgery and other types of lens replacement procedures. The main difference between these two types of IOLs is the way they interact with water and other fluids in the eye.

Hydrophobic acrylic IOLs are made from a material that repels water and other liquids. This means that they do not absorb fluids, and are less likely to develop cloudiness or haze over time. They are also less likely to attract bacteria and other microorganisms, reducing the risk of postoperative infections. Hydrophobic acrylic IOLs tend to be more rigid and have a higher refractive index compared to hydrophilic IOLs.

Hydrophilic IOLs, on the other hand, are made from a material that attracts water and other fluids. This means that they can absorb fluids in the eye, and may be more prone to developing cloudiness or haze over time. They are also more likely to attract bacteria and other microorganisms, increasing the risk of postoperative infections. Hydrophilic IOLs tend to be softer and more flexible than hydrophobic acrylic IOLs, which can make them easier to implant and position within the eye.

Finding The Right Lens

With the advances in technology and health care, patients are better informed and have higher expectations of cataract surgery than ever before.

Patients should be introduced to all IOL options so that they, along with their surgeon, can select the best lenses to fit their individual needs and lifestyles.