NEW OPTIONS IN OPTICAL DESIGN

Innovations in optical design are increasing the number of patients in whom multifocal IOLs could achieve their desired effect, according to a series of presentations at the XXX Congress of the ESCRS. “New options out there give us a broader range of patients to whom we can offer these lenses. And patients now have the choice of close-reading vision or intermediate vision, and we also now have the ability to correct astigmatism with multifocal toric lenses as well,†said Andrea Y Ang MD, MBBs, MPh, cornea fellow, Cincinnati Eye institute, Cincinnati, Ohio, Us.

She noted, for example, that AcrysofR ResTOR (Alcon) is now available in four different designs covering a broad range of visual requirements. Patients now have a choice of a toric or non-toric version with near adds of 2.5 D or +3.0 D. Patients who require good intermediate vision are likely to benefit from the newer, 2.5 D version. The ResTOR lens has an apodised diffractive structure consisting essentially of nine or seven concentric diffractive rings of different widths. The width between the steps determines the power of each ringsector and the step height that controls the lens’ light distribution, Dr Ang said.

The new 2.5 D near add version of the ResTOR lens differs from the +3 D in having only seven diffractive rings instead of nine. in addition, 100 per cent of the central zone of the new lens focuses light from distance object, compared to only 40 per cent in the older lens. The optic’s outer, distance-focusing area has been increased by six per cent and the apodised diffractive area has been decreased by 18 per cent. “The early users of the ResTOR +2.5 D add multifocals believe that it performs better for their patients in activities involving distance vision. The +3 D lens is better for reading a book or for reading small print and other near activities like that, and the 2.5 D lens is better for watching television or using the computer,†Dr Ang added.

The toric versions of the ResTOR have the same basic design as the non-toric lenses but have a posterior toric surface with posterior toric axis marks like those of non-multifocal Acrysof toric IOLs. They are available in cylinder powers of 0.68 D to 2.05 D at the corneal plane, 1.0 D to 3.0 D at the IOL plane.

Small incision toric multifocal

Another toric multifocal, the AT LisAR (Carl Zeiss Meditec), is especially designed for small incision cataract surgery and has produced good results for near and distance vision, said Roberto Zaldivar MD, Buenos Aires, Argentina. The IOL has a diffractive aspheric back surface and an aspheric toric front surface. The lens provides a theoretical addition of +3.75 D at the IOL plane. It is available in cylinder powers of 1.0 to 12.0 D in 0.50 D increments.

In a study involving 22 eyes with 1.0 D to 4.0 D of astigmatism, the distance visual acuity was 20/20 or better in 70 per cent of eyes and 20/25 in remaining 30 per cent of eyes at six months' follow-up. In addition, the near visual acuity at a distance of 40cm was 20/20 in 75 per cent of eyes, 20/25 in eight per cent of eyes and 20/50 in the remaining 17 per cent. Intermediate vision was on average 20/40 or 20/50 at distances of 60cm to 80cm.

Furthermore, of 12 patients who received a questionnaire about their quality of vision, eight said they had no problems with night vision and only four said they had moderate difficulties. On the other hand, eight reported moderate difficulties with glare at night. “All said they were satisfied with the surgical results. All patients also said that, given the choice, they would again opt for the AT LisA toric multifocal iOL and that the surgery did provide them with the result in achieving spectacle freedom,†Dr Zaldivar said.

Radial sectors

Another of the new IOLs, the Lentis MPlus (Oculentis), Like the Acrysof ResTOR, has one version suitable for those who want to read small print and another version for those to whom intermediate and distance vision is more important, said Prof Jorge L Alio MD, PhD, VissUM, instituto Oftalmologico de Alicante, Alicante, spain.

The Lentis Mplus is based on the concept of rotational asymmetry. instead of the concentric sections providing different foci, the lens is divided into two different radial sectors, the largest sector and the central zone focus light from distant objects and the smaller sector focuses light from near or intermediate objects, depending on whether the lens has a +3.0 D add or + 1.5 D add.

“The potential advantages of having radial sectors instead of concentric rings include better contrast sensitivity, less haloes and less glare,†Dr Alio said. he noted that he and his associates have been implanting the new multifocal lenses in patients for the past three years and the results achieved to date suggest that the lenses provide good spectacle independence, with contrast sensitivity close to that achieved with monofocal iOLs.

Around 50 per cent of eyes implanted with the new lenses have achieved an uncorrected distance visual acuity of 20/20 or better and around 60 per cent of those with the +3.0 D add version have achieved an uncorrected visual acuity of J2 or better. in addition, 83 per cent of eyes with the + 3.0 D lens achieved both a distance visual acuity of 20/32 or better and an uncorrected near visual acuity of J3. Among patients with the +1.5 D lens, 54 per cent achieved an uncorrected distance visual acuity of 20/32 or better, and an uncorrected intermediate visual acuity of J3 or better.