EDOF Lenses and the Hidden Power of Contrast Sensitivity: What 9,000 Patients Taught Us

Last week I'v been talking at the biggest Ukrainian Ophthalmic conference OphthalmicHUB 2025, and I was sharing my data from 9,000 patients from IOL-adviser.com web site, showing how the real-world patients across the globe wants to see, and how these needs are matching with modern EDOF IOLs.

Special attention was taken to contrast sensitivity, an issue which is always underestimated, but vitally important for high quality of functional vision. And interestingly, quite often contrast sensitivity is misunderstood by both - ophthalmologists and for sure patients.

Here is a vide of my presentation here, and full transcribed text below.

Good afternoon, dear colleagues. Many thanks to Professor Vitovska for the invitation and the opportunity to share my experience and possibly provide new insights and tools for your work.

And today I want to start with some interesting numbers.

As you probably know, part of my work is the YouTube blog Non-Ophthalmologist in Ukrainian and IOL-adviser in English and besides the blog, I am managing the IOL-adviser.com website, where patients can get basic information about lenses. The main thing is to get help in choosing a lens through automated tools. And on my side, I get information about real vision issues, patient needs — a win-win situation. And today I want to share with you some data that I'v presented last year at the “Ophthalpreneurs” conference in Italy. It’s a conference about refractive cataract surgery in the private sector, organized by Francesco Carones. And I’ll show some key slides from here, adding one slide that I deliberately didn’t show last year.

So, I have gathered 9 000 unique responses to Dr. Dell’s questionnaire. This is a well-known questionnaire, it’s available publicly. A questionnaire that helps doctor and patient to choose a lens, to understand the limitations of presbyopic lenses and choose, let’s say, the direction to go — into monofocals, EDOFs, trifocals, full range of vision, etc.

Unlike the paper version, this questionnaire on my site gives an automated response — it calculates the patient’s score, gives an automatic answer that the patient can take to the doctor and discuss clinical limitations, models, etc. So, it’s a tool to facilitate the workflow. And of course, I collected data, and here’s what I got.

First, who are these people? As you can see, 90% are over 40, and even 15% are over 70. So, this is our target audience — 9,000 people who are presbyopic or cataract patients. And now there are results of the lens selection. The lenses suggestion wich patients received as an initial recommendation to bring to their doctor.

As you can see, 30% are monofocals, but importantly, 61% are lenses chosen by patients who don’t want to wear glasses. That means that the segment of presbyopia-correcting lenses important to people. More than half of patients need that! And have a look: 32% of this segment is MonoVision.

And what is MonoVision? In the questionnaire, MonoVision is when a patient consciously chooses maximum night vision quality or absolutely cannot tolerate night-time dysphotopsia.

And, by the way, MonoVision is kind of an alternative to achieve vision without compromises between near and far. And yesterday, thanks to Professor Lutsenko and Dr. Kavalov, we had a good discussion about MonoVision — because it also has its limitations. Having the basec MonoVision earlier as a reasonable option for presbyopia correction, nowadays it makes no sense as now we have enhanced monofocal lenses for mini-MonoVision, and modern EDOF lenses for micro-MonoVision if clinically indicated for the patient.

And what’s interesting — if we go back to that slide — note that MonoVision was recommended for 32% of patients. If you will think about it deeply, that’s 50% of patients who want something from the EDOF segment. And it’s easy to make the wrong conclusion that maybe full range of vision — trifocals — are no longer needed. There’s only about 10% here — not a lot. But no.

In my experience, patients who truly need a full range of vision are nearly guaranteed to convert to the premium segment. They want it, they strive for it, they’ll get it.

In these 50% who are supposed to be an EDOF segment — patients split into the two groups. One group ends up with an enhanced monofocal lens simply due to budget constraints. The other group might choose full range of vision after consulting with the doctor. Because sometimes, patients reflect and think that maybe these halo effects are not as scary as the desire to see small print up close without glasses — what is delivered by full range vision lenses. That’s the story we’ll discuss later today. Important is that is it a real-world data — how your patients really want to see.

Now, back to EDOF IOLs.

The EDOF segment has been created in 2014 by the Symfony lens, which is well known to you. It had a diffractive echelette design and was sometimes mistakenly seen as a multifocal lens. But it isn’t — we’ve talked a lot about this. It’s an EDOF lens, just based on diffractive technology. Then, the era of non-diffractive technology began in 2019 — also by Johnson & Johnson — with the Tecnis Eyhance. But I want to note: Eyhance is not an EDOF lens in the sense of criteria defined by the American Academy of Ophthalmology or ESCRS. It’s an enhanced monofocal lens, though the internal technology is an EDOF based. The first true non-diffractive EDOF lens was Alcon’s Vivity, well known since 2020, with its X-Wave technology — well visible in the central optics its core element which refracts the light into a single elongated focal point.

Then in 2024 J&J released Tecnis PureSee, a fully refractive lens using completely different technology, with no visible optical elements. We’ll discuss it details shortly.

And now, let's focus on what is important if we are talking about presbyopia-correcting lenses.

Here we should focus on three key components: first — the defocus curve; second — positive dysphotopsia or night halo effects; third — possibly the most underestimated yet most critical for functional vision — the contrast sensitivity.

We need to discuss contrast sensitivity thoroughly. Because in many real-life situations, it’s more important for human functioning than the visual acuity.

There have been publications on this since 1987 (which I’ll mention today), maybe earlier, and even newer publications from 2022–2023 in literature. Driving, facial recognition, signs, emotions — all rely on contrast sensitivity under low contrast conditions. There are two parts: the patient’s subjective contrast sensitivity and the Modulation Transfer Function (MTF) of the optics. A patient’s contrast sensitivity depends on many factors — corneal condition, tear film, retina, axial length, vitreous, optic nerve, the visual cortex etc.

But if we take two identical patients (theoretically), whether healthy or with retinal or glaucomatous conditions, under the same conditions, and implant two different lenses — one with lower MTF, one with higher MTF — the patient will have better contrast sensitivity with the higher MTF lens.

What is MTF — or Modulation Transfer Function? Briefly: MTF describes how optics transfer fine detail and contrast. 

If you will look at the world around you, you will notice large objects, like chairs. They are large and have fewer elemenets per space that is low spatial frequency. And fine details like texture of fabric have more elements per space or high spatial frequency. And all these frequencies have different contrast. And we combine all this on one graph.

One lens or optical system can transmit, for example, 40% of visual information at certain contrast and frequency levels, and another can transmit only 20%. Transmitting 100% across all frequencies and contrasts is physically impossible. That’s a limitation.

So MTF essentially merges resolution and contrast into one metric.

As you see in this image: top left — crisp, detailed; bottom — less defined, blurry. When we think of contrast loss, we often imagine such type of images.

That’s wrong!

Contrast loss is actually the loss of image detail, or entire visual elements in shadows. And this is explained by the Spatial Vision Theory — a critical element in understanding of how do we see the world. It’s also the principle behind digital cameras — your phone camera works on this.

Briefly the idea is the following: visual information consist of elemental sinusoidal patterns with varying orientation, brightness, and spatial frequency. All the information we see is decomposed into those elemental patterns. Then, in cameras, mathematical Fourier transforms recompose the image from those pieces. In the human visual system, similar computations happen — not like a phone, but conceptually close.

These transformations rebuild the image from elements into a whole picture we see and perceive — like in this face example. First, we just see a person. And then magic happens our brain combines high contrast and large objects and low contrast fine details to a complete image. And we see a person and recognize emotions.

So, important point here is that contrast loss means the loss of details — or even entire components — especially in shadows!

This is a slide from an interesting 1987 study by Arthur Ginsburg — available online — which discusses all this thoroughly in an ophthalmology context. So, when we talk about losing details with a lens, we imagine a slightly lower-quality image as I said. And we think “It’s not good, but it's okay to live with it, nothing special”

But no — it’s about unrealistic images, where parts of the image or entire low contrast objects in the shadows may dissapper, like pedestian on a dark road. This is the problem.

And how do we avoid it? By using an IOLs which keeps as much of contrast as possible and that's why transmit more contrast-rich images to improve patient contrast sensitivity and needed details.

Today we have such a lens — Tecnis PureSee — a fully refractive lens we talked about yesterday.

I’ll skip technical details as all of you either know or can google it. Let's talk about important things. Back to the three key elements — defocus curve, dysphotopsia, contrast sensitivity.

Defocus curve: identical to the well-known Symfony, and we already have a lot of clinical experience with both Symfony and PureSee. Some of your colleagues who’ve used PureSee say that it works at least as good as Symfony and sometimes even better.

Another critical factor related to defocus curve is a tolerance to refractive errors, especially important for complicated eyes — hyperopes, high myopes — but really for everyone.

Have a look at the interesting comparison. Look at Eyhance vs PureSee. That lower zone is larger for PureSee — these are patients who got uncorrected 1.0 distance acuity. It’s larger for PureSee. The second, darker zone is 0.8 to 1.0 acuity — smaller for PureSee. So PureSee gives you more safety.

Next — the magic explained by physics. PureSee has no distinct optical zones, so there’s nothing to distort light sources. As said yesterday — virtually zero patient complaints of night dysphotopsia. That’s very important. 

Contrast sensitivity — again, crucial. In PureSee, contrast sensitivity is comparable and almost identical — to Eyhance. But, let’s recall what Eyhance gives in terms of optics. We said “everything is fine,” but let’s compare, maybe Eyhance isn’t as perfect as we think.

Here’s official optical bench testing data from JNJ — publicly available. They tested various lenses. Eyhance has slightly lower MTF than the basic Tecnis monofocal, but in wide pupils and low-light conditions, it performs 31% better than standard monofocal lenses, including Alcon Clareon. That means better contrast sensitivity potential overall.

What about PureSee? Same test — optical comparison with similar lenses. Big difference here — PureSee vs Vivity — especially 36% better in low light. Again, it’s about giving patients more contrast, better visual quality — simply better vision.

Next — this part is personal. I'm planing a refractive lens exchange due to my high hyperopia.

And I want to compare two worlds — which I believe no one has yet done. I compare MTF on the same scale for monofocals vs EDOFs — Eyhance, PureSee, Vivity and monofocal Clareon. And look at this magic. In low-light, where all compromises of presbyopia correcting IOLS are well noticeable, with a 5 mm pupil, monofocal Clareon performs slightly worse than presbyopic PureSee. That’s amazing.

So what does that mean to me? First, personally — it inspires me. Second — 61% of patients want to see without glasses — remember that. We now have PureSee — good range of vision. Not as wide as Synergy — but with no night-time visual effects. No contrast loss in low light comparing to well known monofocal. So we can expand the range of patients to whom this lens can be safely offered, isn't it? That expands your candidate pool, and with better tolerance to refractive error, this lens gives you more safety in daily practice, especially with complex eyes.

Oleksii Sologub

MSc, LLB, MBA

Premium IOL Clinical Integration

Patient Communication & Conversion Strategy

Board-Level Advisor in Ophthalmology