These variables include internal aberrations caused by the shape of the lens as well as the interaction between pupil size and the IOL’s refractive or diffractive characteristics, said Dr.
Hoffer, a clinical professor of ophthalmology at the University of California, Los Angeles. The most obvious of the variables is the optical approach used to achieve multifocality.
In clinical studies, patients with the nontoric version of AT LISA had binocular central intermediate acuity, at 70 cm, of 0.27 to 0.34 log MAR (approximately 20/38 to 20/45). “I used the [nontoric] AT LISA extensively a couple of years ago,” said Erik L.
Mertens, MD, medical director and eye surgeon at Medipolis in Antwerp, Belgium.
“My favorite multifocal IOLs are diffractive, and they represent a growing percentage of my total IOL share,” said Dr. “In my opinion, diffractive IOLs provide more consistent results on average [than refractive lenses].
And each design represents a different solution to the central dilemma of multifocal lens design: how to divide up incoming light to optimize distance, intermediate, and near vision.
The single-piece, aspheric AT LISA, available in toric and nontoric versions, is a refractive-diffractive hybrid lens with 3.75 D of near add (Fig. The lens directs light to one focal point for distance vision and another for near vision, requiring the patient to neuroadapt to the presence of two simultaneous images. The lens has stepped, concentric rings of alternating power that, independent of pupil size, divide usable light 65 percent for distance and 35 percent for near.
The concentric diffractive rings on the posterior IOL surface are divided into main zones and phase zones; the latter zones assume the function of the steps of diffractive IOLs.
AT LISA rounds off the sharp edges of the optical steps on its surface in order to reduce the internal reflections that cause glare and halos at night.