Glasses – How do glasses actually work?
For many people, the day only begins to take shape when they put on their glasses in the morning, and their vision is sharper. But how do glasses work, and what exactly is a frame made of? Normal-sighted eyes have no problem seeing objects near and far in focus without any issues. In eyes with normal vision, the lens focuses the light rays entering the pupil so that they meet on the retina inside the eye. The lens is flexible up to a specific range and can thus compensate for minor visual impairments and different distances. If the lens cannot focus the light on the retina in this way, the receptors can only transmit a blurred image.
myopia and farsightedness
All short-sighted people can see close objects perfectly sharp – but distant objects only imprecisely. This is due to the not quite exact “construction” of the short-sighted eye: This is either a little too long, and the lens bundles the incident light rays before they fall on the retina at the back of the eye. Or the refractive power of the lens could be better. As a result, the image impinging on the retina is slightly blurred.
Precisely, the opposite is the case with the far-sighted eye. This looks good at a distance but struggles up close, typically when reading. The reasons: Either the refractive power of the lens could be better – or the eye has grown a little too short. As a result, the lens only focuses the light precisely on the retina a little later. The image information hitting the retina is blurred.
What do glasses do?
The single-vision glasses in front of the eye cause additional bundling of the light (in the case of long-sightedness) or scattering (in the case of short-sightedness ), with the result that the light rays meet precisely in the centre of the retina—the result: a sharp look.
The glasses frame
Compared to the lenses, a frame is quite simple at first glance: one frame, two temples, one nose pad, done? Not even close. There is also a great deal of engineering know-how and creativity in eyewear frames. It starts with choosing the suitable material: Steel? Sheet? Titanium alloys? Plastic? Horn? Or a combination?
The possible variations are almost endless, but so are the difficulties that must be considered when designing the frames. Because only some types of material can be easily combined with every other, once these technical problems have been solved, there are different requirements that the wearer places on his glasses. These are highly contrary: the model should be chic, light, flexible, skin-neutral, sweat-resistant – and ideally super cheap.
Almost anything is possible: the engineers’ answer to the demand for “flexible temples”, for example, can be either cheap (spring hinge) or elegant (highly flexible metal alloy). Whether glasses for allergy sufferers are made of allergy-free materials or are coated with a thick coating that ensures compatibility also affects the price and appearance.
Glasses: constantly in development
The nice thing is that new production methods and materials constantly push their way onto the market, allowing designers to keep reinventing glasses. A few years ago, flexible, pliable metal was still in high demand, but today, the trend is towards plastic again. However, this was introduced with the same material properties as metal glasses. What seemed impossible just a few years ago is now available from opticians.
