80 % of all the information our brains receive is via the eyes. But as well as the magic of sight, it also has its defects. At least 47% of the UK population suffer from Ametropia and should wear spectacles from the age of 16 and up (Source: The Global Need for Refractive Correction, University of Oxford, 2008). The problem can be quickly identified with a vision test.
Whether an individual is far-sighted (only distant objects are seen sharply), short-sighted (only near objects are sharply reproduced on the retina), astigmatic (vision is blurred or distorted due to a warped cornea) or presbyopic (cumulative short-range ametropia) – the right spectacle lenses are out there for every visual defect.
Our eyes function like a precision camera. The cornea and lens of the eye represent the camera lens. They concentrate the light rays and project them accurately onto the retina. The accommodation is a sort of focusing system of the lens. It is comparable to a camera in that it makes it possible for us to accurately see objects both at a distance and up-close. However, only a small minority of people can rely on eyes that function that well.
Only 58 percent of non-spectacle wearers over the age of 40 achieve full visual acuity. In the Europe and even among spectacle wearers, only 66 % achieve pin-sharp vision. (Source: Allensbach survey 2006).
For this reason, starting at the age of 40 at the latest, everyone should have an annual eye and vision test. An ophthalmologist can check your visual acuity. The good news: The right spectacle lenses are out there for virtually every visual defect, regardless of the form of ametropia.
An ophthalmological test should be also conducted regularly to check for further abnormalities and organic changes to the eye.
The shortfall in the eye’s refractive power is balanced by a corrective concave lens so that the image is once again sharply reproduced on the retina.
The excessive refractive power of the eye is balanced by a corrective convex lens so that the image is once again sharply reproduced on the retina.
The uneven refractive power of the eye is balanced by a corrective cylindrical lens so that the image is once again reproduced sharply and undistorted on the retina.
The failing refractive power of the eye in the near range is re-balanced with a corrective convex lens (reading spectacles). As a result, near objects are once again sharply reproduced on the retina.
Single vision lenses
These spectacle lenses have a uniform corrective effect over the entire surface of the lens. They facilitate sharp and relaxed vision for the spectacle wearer at all distances.
The eye itself still undertakes the necessary acuity adjustment for seeing at various distances, for example when reading. Reading glasses for presbyopia are an exception, as the spectacle lenses used are optimised for short distances.
Thanks to the most modern technology, it is now possible to keep the weight of spectacle lenses to a minimum. Even for severe cases of ametropia, there are slim, flat and light spectacle lenses with high wearing comfort.
With many ZEISS products, even the colourless spectacle lenses absorb so much UV light that optimal UV protection is provided under normal weather conditions.
As the name suggests, these spectacle lenses contain two (= the prefix “bi”) optical effects – for near and far distances.
For natural-glass bifocal lenses, the dioptric value required for the near range is achieved by a fused additional lens in the bottom part of the glass. For organic-glass bifocal lenses, the near range effect is achieved by a moulded additional surface with a small front face radius. Bifocal lenses are now being overtaken by progressive lenses.
Besides enabling the wearer to see far and near, they also have an additional, third intermediate zone for medium-range vision (50 cm to 1.50 m). Trifocal lenses are also increasingly losing importance due to progressive lenses.
Innovative stars – the modern, now-available progressive lenses offer key advantages over bifocal and trifocal lenses: Progressive lenses make sharp vision possible at all distances. There are no image jumps in the visual field, nor is there a separating edge.
As early as 1983, ZEISS was setting new standards for progressive lenses with its Gradal HS solution. The acronym HS stands for Horizontal Symmetry. It ensures homogenous visual impressions for the right and left eye in eye movements.
Thanks to Gradal Top E, the ranges of vision, and especially the intermediate range, could be widened substantially and were further adapted to the physiological requirements of the user. The first customised progressive lens by Carl Zeiss was used in 2000 and has been further developed to this day. The latest generation is called ZEISS Progressive Individual2. The functional surface can now be optimised for each individual effect. In addition, the individual features, such as inter-pupil distances, tilt, distance between the vertex of the cornea, frame size and the near-range primary working distance were all taken into consideration.