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What is CTF?
Fred Wassenburg: CTF stands for continuous transitional focus. Most multifocal IOL designs – bifocals and trifocal – generate multiple foci on the retina. So with a trifocal IOL, this means a harsh change between distance to intermediate, and from intermediate to near. CTF optics achieve a continuous, smooth transition from distance through to near, with good, usable vision in between.
How do the Precizon Presbyopic IOL’s CTF optics work?
FW: It is a refractive lens with two distinct foci in the optical zones, and there is some refractive ‘magic’ in the transition zone between those distinct foci, which results in a smooth transition in focus. The ‘magic’ essentially takes a sharp image and elongates it so that it creates a workable image on the retina, which achieves a very nice defocus curve between infinity to intermediate, and from intermediate to near. Where other multifocal IOLs’ functional vision drops off, ours retains it.
Ramón Ruiz Mesa: Everything within optics is a matter of compromise. There is only so much light that you can use. But the patients that have been treated so far are all happy with the comfort of the lens – without having this drop between the foci.
What other advantages does CTF have?
RRM: We’ve found that neuroadaptation in patients is much quicker with the Precizon Presbyopic IOL than other lenses. It feels more like natural vision and they rapidly find their vision to be comfortable and acceptable.
FW: It’s also a very forgiving lens. The multiple zonal design that we chose maintains the light distribution on the foci, regardless of whether you tilt or decenter the lens, and the same distribution and exposure of the lens is maintained, irrespective of pupil size or decentration. It’s a completely new optical approach. And the CTF design means that the lens can be implanted in patients with middle-to-high angle of kappa and even those with a greater than normal pupil diameter under mesopic conditions.
All this can give the doctor comfort. Many IOLs have been optimized for the optical bench – but the human eye is not an optical bench... Unlike benches, you can’t perfectly align, outline and center an IOL in a human eye. On the bench, under laboratory conditions, ours might not be the best lens around. But if any slight decentration or tilting occurs, our lens has far more predictable – and a smaller bandwidth of – outcomes.
And does that open up a greater patient population?
FW: Thanks to the optical compromises inherent with all multifocal IOLs, patient selection remains important – even with our lens. If someone has unreasonable expectations of postoperative vision – like ‘eagle vision’ at all distances – they’ll be disappointed. But people with reasonable expectations will have a balanced outcome, and doctors can be sure that they will always be within the same narrow bandwidth of results. Further, because our lens is a refractive lens design, it’s less prone to photic phenomena than multifocal IOLs with Fresnel rings or diffractive optics.
What kind of patients should be recommended the CTF lens?
RRM: The typical multifocal IOL candidates – patients that want to achieve
You’re one of the first surgeons to implant a Precizon Presbyopic IOL. What made you want to try it?
RRM: I was very familiar with the Precizon IOL family and had implanted many monofocal and toric Precizon IOLs with great results. I could see the potential of this completely new CTF optical design approach – and that’s why I wanted to participate.
What were your patients’ visual outcomes like, and how happy were they with their postoperative vison?
RRM: The visual results from the defocus curve, contrast sensitivity and patient satisfaction were all satisfactory. The uncorrected visual acuity obtained with this new lens was good for all distances (far, intermediate and near) with low rates of photic phenomena.
Would you implant this lens in a family member or friend?
RRM: Absolutely! I implanted one in a great friend of mine – a celebrity chef from my city, who suffered from both hyperopia and presbyopia. He now has a good visual acuity at all distances and is spectacle independent. He’s beside himself with happiness! I want to offer the best to my patients and friends – and this technology is it!
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