Today’s prescription spectacle lenses are a miracle of technology. HELEN GRANGE tried the Zeiss experience
If you’ve been for an eye test, you’ll be familiar with the big letter “E”, and if your vision is poor, you’ll know well the squinty effort you have to make as your eyes descend the chart and the letters get smaller and smaller.
It’s called the Snellen chart, and it made Dutch ophthalmologist Herman Snellen famous when it was first published in 1862.
For the next 100 years, eye testing remained virtually unchanged. Fast forward to today, and technology has been added to this old eye examination procedure to the extent that your provisional prescription can be determined without you having to read out any letters.
This is because the global optics company Zeiss has developed instruments that do the job, and all it entails is pressing your forehead against the frame of a sophisticated computer which analyses the “fingerprint” of your eye, enabling the optometrist to determine your prescription to the nearest 0.01, instead of 0.25 as in older eye tests.
I did a test run of the Zeiss experience test at the Mellins-Zeiss Vision Centre in the new Mall of Africa, and it takes about 45 minutes, of which only about 15 minutes is spent effortlessly looking through three hi-tech testing machines, one of which does incorporate the Snellen chart.
The rest is spent telling your optometrist what you expect your eyes to do, be it working long hours on a computer, seeing clearly for hours of night driving, reading for hours or playing sport, in order to customise your spectacle lenses or contact lenses, and to help you choose frames that are right for your face and, importantly, your vision.
The machine that does the remarkable “fingerprinting” work is called a Zeiss i.Profiler, which digitally maps about 2 500 points on each eye in under 90 seconds. This machine enables Zeiss to manufacture arguably the world’s most individualised lens.
“On the digital map produced, the green colour indicates the least distortion of light that enters and exits the eyes, and the yellow, red and blue colours demonstrate irregularities in the eyes,” explained André Horn, senior optometrist and managing director of Mellins i-Style.
The Snellen chart still has a place in the process. It’s the subjective eye test you’re familiar with, where different lenses with varying strength are placed in front of your eyes and you’re asked to describe what and how well you see.
The last step in the Zeiss experience is about how the lenses fit the spectacle frame and the effect of the positioning and shape of the frame on your lenses.
Lens-fitting errors can reduce optical performance by up to 40 percent, so in this step, Zeiss lens configuration technology, the i.Terminal (accurate to 1/10 of a millimetre) is used to optimally position the lenses.
It also calculates the effect of the positioning and shape of the frame on the lenses, so that your precision lenses can be manufactured and fitted more accurately.
All this data is then sent to the Zeiss computer server in Germany, which is used to manufacture optical lenses, called i.Scription, which are perfectly customised for each of your eyes.
“The lenses are able to provide clearer night and twilight vision, reducing irritating reflections or halo effects, and you can obtain improved colour vision and contrast. In essence, you’ll be able to see more clearly,” said Horn.
You also get to choose the lens thickness by choosing from various index lenses. Your lenses can therefore be up to 50 percent thinner and lighter. All the Zeiss lenses come with UV coating as standard.
You can also choose a Zeiss Photofusion lens that will turn dark in the sun and light indoors.
Zeiss has also introduced DriveSafe lenses, everyday lenses specifically designed to improve vision, focus and comfort on the road. The DriveSave multifocal lenses provide up to a 43 percent larger mid-distance viewing zone to quickly refocus between the road, dashboard and mirrors.
The lenses also reduce perceived glare from oncoming traffic at night, which improves vision in low-light conditions, making driving in the dark safer.
Radio and TV presenter John Walland is a Zeiss lenses wearer, and says it has enhanced his ability to do his job. Mellins i-Style is contracted in by most medical aids.
Have your eyes tested
Your optometrist will examine not only the quality of your vision and ascertain your visual needs, but will also inspect eye injuries, abnormalities and early signs of conditions such as cataracts, glaucoma and macular degeneration before you’re aware of any symptoms, many of which can be treated if detected early enough. Your eyes’ ability to function as one will also be evaluated.
Prolonged conditions such as diabetes, high cholesterol and high blood pressure can be detected during an eye examination.
Children, especially, should be regularly tested, says André Horn, senior optometrist and managing director of Mellins i-Style. “Sight is directly connected with academic development as children with undetected vision problems will regularly have trouble with their schoolwork. Often children will not mention if they have a problem with their sight simply because they don’t know what it means to have 20/20 vision.
“Also, without regular eye examinations, it can be difficult to determine whether a child’s sight is developing normally and if they have the necessary vision skills to perform well at school,” he says.
“Optometrists recommend that most people should get their eyes tested every two years, with more frequent eye tests if you are a child wearing glasses, have diabetes, are aged 40 and over, and have a family history of glaucoma,” says Horn.