What's the best way of developing spectacle lenses tailored to our digital lifestyle?

You might think people have already created spectacle lens solutions for every conceivable vision-related problem – but it turns out that's not the case. ZEISS decided to take a closer look at how vision works in our new digital world of regular smartphone and tablet PC use – and the results were nothing short of astonishing. The findings led to the development of a vision solution that provides effective relief from eye strain. Keen to discover what lay behind the development of ZEISS Digital Lenses, BETTER VISION decided to interview Timo Kratzer, who heads up the development department for lens design and patents at ZEISS.

Timo Kratzer: The development of Digital Lenses was a lengthy process, and the idea behind the development came from many different sources. These included, feedback from opticians and consumers, the results of the wearer trials that we regularly carry out for our lens products, and the data from our lens production processes which we constantly evaluate.

Digital devices, such as smartphones and tablet PCs have become our constant companions, something that we are continually looking at and browsing. We decided to analyse people's vision in this context because we saw that many people between the ages of 30 and 40 were suffering from tired, strained eyes, particularly in the evenings. In some cases, people didn’t realise that it was getting harder to focus on close-up objects, they simply felt less relaxed and comfortable than they did before. In many cases, they were having to hold their smartphones, iPads and other devices further and further away from their eyes in order to focus properly.

Our findings showed that this stems from a combination of multiple factors. Firstly, the eye's ability to adjust its focal length to different distances – what we refer to as accommodation – is already starting to deteriorate by the time people hit their mid-30s. That's something that tends to creep up on us without us really noticing it. Secondly, smartphone use in particular – though this also applies to reading the newspaper – requires us to switch our gaze from a close-up viewing to distance vision much more frequently than usual. Our eyes are continuously having to focus on varying distances. This causes strain, especially if the eye muscle's flexibility has deteriorated due to the hardening of the crystalline lens. And, thirdly, it involves a different visual distance to the one we're familiar with for reading, for example. Reading materials used to be the closest things we focused on with any great frequency, but now people hold digital and mobile devices much closer to their eyes than a book.

Timo Kratzer: Yes, the ZEISS Digital Lens design is also available in a tinted version and as self-tinting lenses. For people wearing glasses for the first time who don't need any distance correction, it's also possible to simply design the upper part of the lens without optical power and confine the support for close-up vision to the lower part of the lens.

Timo Kratzer: Intensive wearer tests are critical when it comes to developing new lens designs. We always want to know exactly how our design will work for different people on a day-to-day basis. For example, whether it will offer real improvements and be well tolerated. So we recruit a group of testers who follow a standardised process and provide us with a detailed account of the positive and negative aspects of each new lens. That enables us to compare designs based on slightly different calculations and continuously optimise our calculations until we get things exactly right.

Timo Kratzer: As we get older our eye’s crystalline lenses get harder. If we're constantly switching between close-up and distance vision, it can be very tiring for our eyes, and that's what we refer to as digital eye strain. It doesn't necessarily mean that your eyes can no longer focus on objects at certain distances, but rather, that they take longer to do so and have to work harder in the process. I've noticed it myself, for example when my little boy had a splinter in his finger and I was trying to remove it with tweezers. You have to look at the finger very closely, but nowadays I have to hold his finger further away to get it in focus, because close-up vision is simply becoming more difficult.

We've actually developed a test to determine whether people’s eyes are showing the first signs of digital strain. You switch between looking at a display and looking into the distance and the test analyses how quickly your eyes re-focus on each respective distance. This test can be performed by your ZEISS optician or you can even carry out a quick test yourself using our free eye strain test app.

Timo Kratzer: There is some debate about whether eye training is effective or not. But what definitely helps is to periodically give your eyes time to relax over the course of the day. You can do that by looking into the distance while keeping your eyes relaxed and without focusing on anything in particular. But they say you need to do it regularly during the day – for five minutes every hour!