The SIFI Mini WELL IOL provides a progressive, extended depth of- focus experience for patients – not just a few sharp foci. How is this achieved? What does this mean for patients? And who are the best candidates? Gerd Auffarth shares his thoughts.
How does the SIFI Mini WELL work to give progressive depth of focus?
By having two concentric central zones with spherical aberrations of opposite sign, and an external monofocal zone (Figure 1).
The key concept is that it doesn’t use the diffractive principle of having different foci. Instead, the lens optics has zones of different asphericity with a refractive central zone that translates to around 2.5 D in near, with optically efficient transition zones, to give a good quality of vision across all distances (Figure 2).
What are the advantages of the aspheric approach over other approaches to multifocality?
There’s a big problem with a lot of multifocal or extended depth of focus (EDOF) lenses, and that’s the loss of light energy that’s inherent with diffractively separating the incoming light to near, intermediate and distance. The Mini WELL’s progressive optics use more or less all of the light that comes in, and it all gets diverted to the retina and used for vision. This also has the advantage of minimizing any issues with contrast loss, halo or glare – these photic phenomena are almost absent with the Mini WELL which, in several of our studies, has proven itself to be similar in optical performance to monofocal IOLs when it comes to these factors. This is a truly EDOF lens – because the patient experiences continuous focus, unlike seeing things sharply at, say, 30 cm for near, then nothing, then back towards sharpness around 80 cm, then very little until you reach 5 meters or so for distance. For the patient, it feels like he or she is accommodating – the eye can zoom automatically between two different distances, unconsciously. In other words, from near to distance, they experience a continuous flow of good-quality images.
What’s it like for the surgeon to implant?
It’s an IOL with four haptics, and this means that you get a very nice and safe fixation in the capsular bag. As it’s a true four-point fixation (unlike a plate haptic), it results in very good lens centration, which is important for an IOL like this – even when the capsulorhexis is decentered. The lens is very thin, and comes pre-packaged, hydrated, in an injector with a special coating that means, in my experience, you don’t need any viscoelastic to inject the lens – you just inject with saline solution.
I usually implant it under irrigation, so I have the irrigation handpiece through the paracentesis and I just inject the lens (without viscoelastic) into the capsular bag.
The lens is so soft and forgiving, that I’d say it’s straightforward and easy to use – even with irrigation.
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