Diffractive-refractive multifocal IOL shows promise

The combination IOL comes in 0.01 D steps, features square-edge haptics and has shown good early results in a small cohort of patients.

Issue: October 2014

BySudi Patel, PhD

The demands of modern living command good vision, not just for the young but for all, irrespective of the culture and host nation. The colossal rise in use of static video display terminals, laptops, palmtops, mobile phones and smartphones has shifted the zenith of visual requirements from distance to near vision. It is estimated that the worldwide number of presbyopes will increase from 1.04 billion in 2005 to 1.37 billion by 2020, and this will affect not just cataract surgery but also the demand for spectacle-free high-quality distance and near vision.

Multifocal IOLs

Today, in many countries, the cost of multifocal IOL surgery is affordable and, in some cases, more attractive compared with monofocal IOL surgery supplemented with glasses. Of the various multifocal IOL designs, some patients prefer diffractive while others are happy with refractive, and there is a gender bias when it comes to patient satisfaction. Generalizing, female patients are less demanding and less fussy, and there is a greater chance of achieving satisfaction when a woman is implanted with a multifocal IOL compared with a man.

In some quarters, there is still resistance to implant multifocal IOLs based on concerns relating to quality of vision and even loss of sensitivity when checking visual fields. We do not have a “crystal ball” clinical test that guarantees if a patient is suited for a diffractive or refractive multifocal IOL. So why not produce a multifocal IOL that combines the optical benefits of both designs? A multifocal IOL that combines the positive optical gains of both diffractive and refractive technologies with a design not expected to affect the sensitivity of peripheral vision would be welcome. But such a multifocal IOL should either reduce or maintain the inherent effects of higher-order optical aberrations such as coma and trefoil. The multifocal IOL should not increase the higher-order aberrations that plague our patients.

Diffractive-refractive combination

The MTO Presbysmart Plus is a biconvex multifocal IOL that features a unique blend of a diffractive anterior surface complemented by an aspheric posterior surface. The combination is tuned to gradually reduce the plus power of the lens in a radial manner from the center to the periphery and minimize the impact on total ocular higher-order aberrations. The unique blend should produce good distance and near acuity by extending the depth of field of the pseudophakic eye.

Presbysmart IOLs are individually customized and available in 0.01 D steps. Do patients need IOLs manufactured to such a high resolution when the ISO standard for IOL power labeling is ±0.5 D for powers 25 D to 30 D? When you combine the typical error in biometry, ±0.4 D, with the uncertainties of refraction and this ±0.5 D standard, it is possible to end up with a few isolated cases in which the end residual refractive error could be ±1.5 D off target. Today’s patients deserve and demand better outcomes. Collapsing the manufacturing tolerance down to 0.01 D effectively nullifies the IOL as the source of any refractive surprises. Reducing the chances of significant refractive surprises reduces the chances of patients requiring glasses, thus reducing the cost of secondary procedures to elevate patient satisfaction. The IOL also features square-edge haptics to reduce the incidence of posterior capsule opacification, thus extending its economic gain.

Preliminary clinical results of the Presbysmart Plus based on a small cohort of cases revealed mean uncorrected logMAR acuity improved from 0.3 to 0.15 between 1 and 3 months postop. Over the same period, average uncorrected Jaeger acuity improved from J4.8 to J2.5 at near, residual equivalent sphere fell from –0.8 ± 0.19 D to –0.6 ± 0.33 D, and patients reported good quality intermediate vision for their daily activities. Furthermore, there was no obvious effect on the visual fields. So far, the clinical results look promising for this innovative combination diffractive-refractive multifocal IOL.

References:
Aychoua N, et al. JAMA Ophthalmol. 2013;doi:10.1001/jamaophthalmol.2013.2368.
Barisic A, et al. Coll Antropol. 2008;32(Suppl 2):27-31.
Cimberle M. Gender differences impact multifocal IOL choice, outcome. Ocular Surgery News. www.healio.com/ophthalmology/cataract-surgery/news/print/ocular-surgery-news/%7B957aa478-4cee-4833-8782-19d6b9eb85ad%7D/gender-differences-impact-multifocal-iol-choice-outcome. Published Dec. 25, 2010.
Holden BA, et al. Arch Ophthalmol. 2008;doi:10.1001/archopht.126.12.1731.
Lafuma A, et al. Eye (Lond). 2009;doi:10.1038/eye.2008.223.

For more information:
Sudi Patel, PhD, FCOptom, FAAO, can be reached at Practitioner Services, NHS National Services, Edinburgh, Scotland, UK, EH12 9EB; e-mail: spatel9@nhs.net.

Disclosure: Patel has no relevant financial disclosures. The views expressed are his own and not those of NHS National Services Scotland.