Article

Bridge the gap between distance and near

Trifocal IOL technology, not available in the U.S., can allow some patients clear vision without glasses.

Multifocal IOLs were introduced in the United States and Europe as early as 1986, and I have had the privilege to be involved with clinical and experimental research on these IOLs since 1990.1 Then, the main contenders were a zonal refractive multifocal IOL (the AMO Array IOL, later modified and rebranded ReZoom IOL) and a diffractive multifocal IOL (introduced by 3M, then acquired by Alcon and marketed as the ReStor).1

We have to keep in mind that these “multifocal” IOLs were usually bifocal, featuring a distance and a near focus plus some scattered light. The ReStor IOL is a good example — it originally had a high near add of 4 D, which gave excellent reading at about 30-40 cm. But the problem was the drop of vision between distance focus and near focus, resulting in intermediate vision of less than 20/40 at 60-80 cm (laptop distance).

To overcome this problem, lower near adds were used (3 D, 2.5 D or 2 D) in later designs. By moving the distance and near peaks closer together, intermediate vision was improved to 20/40 or more, but still lower than both distance and near visual acuity.

A DIVERSION

The latest approach to bridge the “gap” between distance and near focus was the introduction of trifocal IOLs. By diverting some of the light to a third, “intermediate,” focus at about 1.5 D, intermediate vision increased to levels of 20/30 or more, thereby providing useful vision at all distances and avoiding problems using smartphones, laptops or e-readers.

A COMPARISON

Trifocal IOLs were made possible due to advances in manufacturing of the diffractive IOL technology. In the early days of the 3M IOL, more than 20% of the light passing through the diffractive design was lost to scatter (termed “higher diffractive orders”). Today, losses are much lower, and about 20% of the light entering the IOL is used to form the intermediate focus in trifocal IOLs.

The first trifocal IOLs available in Europe were the Zeiss AT LISA trifocal IOL and the FineVision trifocal IOL. Compared to bifocal IOLs, both offer better intermediate vision, but maintain the same quality of vision at distance and near focus. The advantage of a trifocal design is therefore better vision at laptop distance with the trifocal IOL than with a bifocal IOL.

Trifocal trials are happening elsewhere

Clinicaltrials.gov shows six trifocal studies in various stages, primarily recruitment, in Israel, Greece, Australia, Hungary and the Netherlands. The most advanced study is occurring in Israel where the Rabin Medical Center has completed a pilot study. The objective: to determine the visual acuity at far, intermediate and near distances tested with optotypes at different distances from the eyes and tested with defocus addition lenses of patients implanted bilaterally with the POD 26P AY FineVision (PhysIOL).

An extended-depth-of-focus (EDOF) IOL does not provide a near focus, but rather uses “continuous” focusing from distance to intermediate, extending the focus and leading to the name “extended-depth-of-focus” IOL. Comparing trifocal IOLs to EDOF IOLs such as the Tecnis Symfony IOL (J&J Vision), trifocal IOLs offer better near vision than EDOF IOLs, but intermediate vision is better with an EDOF IOL.

When comparing trifocal IOLs and the Tecnis Symfony EDOF IOL (J&J Vision),2 distance and near focus in the EDOF lens still offers a better resolution and contrast than the distance and intermediate focus for both trifocal designs, but the difference in resolution is rather small. Trifocal IOLs provide excellent visual acuities at all distances. Results are much better than with the high-near-add bifocal diffractive designs of the past, mainly due to the improved performance at intermediate distance.

Outside the United States, trifocal IOLs have therefore essentially replaced so-called multifocal IOLs because higher add bifocal IOLs provide better near vision than low-add bifocal IOLs and also offer good intermediate vision. EDOF lenses offer slightly better distance and intermediate, but trifocals are not significantly worse at these distances. On the other hand, trifocals offer dramatically better near vision than EDOF lenses.

THE DOWNSIDES

There is a downside to any “multifocal” technology. Side effects of trifocal IOLs are similar to those of bifocal IOLs. Patients see haloes and glare at night, but most get used to these side effects and have no problems driving in the dark — only about 5% of my patients mention night driving issues. Significant problems with glare and haloes and low-contrast vision occur in about 0.1% to 0.5% of my patients, and I typically recommend an IOL exchange if problems persist after six months.

The IOL exchange for a monofocal IOL should be done on the dominant eye first. This typically resolves the problem in most patients, and the trifocal eye in the nondominant eye does not have to be exchanged.

PATIENT SELECTION

Clinically, I use trifocal IOLs in about 40% to 50% of my cataract and refractive lens exchange patients. Trifocal IOLs are my first choice for those patients who want to read without glasses. Alternatively, I offer extended-depth-of-focus IOLs to those patients who rarely read books but prefer to do so on laptops or e-readers. Monofocal IOLs are my first choice in patients who do not mind glasses and/or who want to preserve excellent night vision.

The key to success is understanding the different IOL properties and in informing patients about the advantages and potential side effects of this exciting technology. OM

REFERENCES

  1. Knorz MC. Multifocal intraocular lenses: overview of their capabilities, limitations, and clinical benefits. J Refract Surg. 2008;24:215-217.
  2. Esteve-Taboada JJ, Dominguez-Vincent A, Aguila-Carrasco AJ, et al. Effect of large apertures on the optical quality of three multifocal lenses. J Refract Surg 2015; 31:666-672.

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