OD News Articles

3rd January 2018

The Evolution of Premium IOLs

by Mark Maraman, OD, MS Chehalis, Washington

Almost 70 years ago, British ophthalmologist Harold Ridley implanted the first intraocular lens. During World War II, he had often examined eyes of injured fighter plane pilots. Noticing that small pieces of acrylic plastic from their shattered canopies did not cause a harmful reaction, he designed a lens implant out of the same material. Dr. Ridley’s invention was met with scorn and dismissal. The mainstream of ophthalmic surgery ostracized him for several decades. Some ophthalmologists considered IOLs a dangerous “time bomb”.

How Things Have Changed

In 2000, about a year before Sir Harold Ridley died, Queen Elizabeth knighted him. His invention had triggered a tidal wave that swept through the world of eyecare. New lens designs, sophisticated instruments and innovative surgery techniques have enabled tremendous advances. Modern cataract surgery has moved beyond simply removing and replacing opaque lenses. It is a refractive procedure that restores vision to 25 million people around the world each year.

Better outcomes with fewer complications have increased demand for cataract surgery. Expectations are heightened among an ever-changing population and cataract patients with active lifestyles often desire less dependence on corrective eyewear. This is driving the demand for premium IOLs that offer a larger range of quality vision.

Join me for a quick review of the options.

Toric IOLs

Toric IOLs were introduced in the late 1990s. Before then, cataract patients with significant astigmatism had the option of astigmatic keratotomy (AK) or limbal relaxing incisions (LRI). But most elected glasses correction following surgery.

About 25% of cataract patients have 1.25 diopters or more of corneal astigmatism, so it’s not surprising that toric IOLs have gained popularity. They make up approximately 75% of premium implants used at PCLI. In our experience with thousands of cases, the vast majority of patients are very happy with their visual outcome. Toric IOLs do not compromise vision or increase the risk of complication over spherical IOLs. They just work!

Current toric IOLs correct up to 4.50 diopters of corneal astigmatism. But, as with toric contacts, proper alignment is essential for good visual outcomes. Misalignment or post-operative rotation can create unwanted astigmatism that sometimes requires surgical repositioning. At PCLI, this repositioning is only necessary in about 3% of cases.

Multifocal IOLs

The first multifocal IOL (Array by Advanced Medical Optics) came to market in the US in 1997. Over the past 20 years, many improvements have been made. The newest designs split light into multiple focal points and provide better quality of vision. They are also available in several “add” powers, so vision can be customized to meet each patient’s near and intermediate demands. In early 2017, a toric multifocal IOL (Acrysof IQ ReStor Toric by Alcon) also became available in the US market.

Although many people adapt to multifocal IOLs and are happy with them, some are not. Challenges can include:

  • Slightly blurred distance vision
  • Ghosting or “waxy” vision
  • Impaired intermediate vision
  • Visual aberrations including glare, halos or starbursts
extended range of focus iols

In 2016, the evolution of premium IOLs took a major leap forward. The first extended range of focus (EROF) IOL (Tecnis Symfony by J&J—formerly Abbott) was approved for use in the USA. Also known as an extended depth of focus (EDOF) IOL, the unique design lengthens the spectrum of focus and provides clear vision at different distances. Best resolution is minimally reduced compared to monofocal IOLs. A toric model is also available that can correct up to 3 diopters of corneal astigmatism.

Rather than splitting light into two focal points, like a multifocal IOL, the Symfony lens lengthens the area of focus. There is a smoother transition of vision from far to near that patients notice and appreciate. In contrast, some patients with multifocal IOLs comment about seeing zones of clearer vision between areas of blur as they adjust their working distance.

    Side view of Echelette

Because light entering the eye through a Symfony IOL is not focused at two distinct points, the glare and halos associated with multifocal IOLs are diminished.

All human corneas have a similar amount of chromatic aberration that degrades image quality. To counteract this, the Symfony IOL utilizes proprietary Achromatic Technology—similar to what is used in high performance camera lenses. As a result, distance vision and contrast sensitivity are only slightly decreased from monofocal IOLs.

    How the IOL works
    Cornea with
    chromatic aberration
    Symfony EROF
    achromatic IOL
    IOL counteracts
    aberration

While the range of focus is extended beyond that of a monofocal IOL, acuity begins to drop off at about 1.5 diopters (67cm). Most patients enjoy excellent distance and intermediate vision, while their near vision (traditionally measured at 40cm) is often in the 20/40 to 20/50 range. Even though the near vision (40cm) tends to be less, for a lot of people it is adequate—simply because many near tasks do not require fine detail acuity, and the quality of the overall vision is improved compared to multifocal IOLs.

When better near vision is desired, we can target mini-monovision with slight myopia (-0.75 D) in the non-dominant eye. This gives patients a wider range of near vision while maintaining excellent binocular distance vision.

If patients have a strong near vision preference, a multifocal IOL may be a better option.

I am quite conservative in my approach to new technology that impacts patients’ vision. So at first, I was skeptical. But after more than a year of experience with the Symfony IOL, I can say that it is appreciably different than its multifocal cousins. The Symfony lens implant has become my preference over multifocal IOLs. Many of my PCLI colleagues feel the same way.

Woman using iPad

Benefits of the Symfony EROF IOL
  • Pupil-independent
  • Continuous range of vision from distance to near
  • Excellent distance
  • Excellent intermediate
  • Good near
  • Only slight decrease in distance vision and contrast sensitivity from monofocal IOLs
  • Reduced visual side effects and night symptoms (halos) compared to multifocal IOLs
  • Available in toric
The future

Future IOL advances will undoubtedly lead to broader ranges of focus. A new light adjustable lens that can be fine-tuned after surgery to maximize visual acuity is expected to enter the market. Also, electro-optical IOLs that use artificial intelligence to adapt to visual needs may be in the future. This concept might sound like science fiction. But with the rapid progress of IOL technology, it may be more realistic than we think.

Conclusion

Lens implants have come a long way in 70 years. I am sure Sir Harold Ridley would be delighted with the new technology and all of the options. But despite the advances, no IOL is perfect for every patient.
Success comes by:

  • Maintaining a good understanding of lens technology
  • Knowing the strengths and limitations of various IOLs
  • Listening to patients and understanding their visual needs
  • Helping them maintain realistic expectations
Questions

If you have questions about any type of IOL, please do not hesitate to contact our optometric physicians. We are always happy to help.

Reference

TECNIS Symfony Extended Range of Vision IOLs, Abbott Medical Optics Inc