Home Therapies Glasses: when are they necessary? Which ones are there?

Glasses: when are they necessary? Which ones are there?

by Josephine Andrews
Published: Last Updated on 421 views

Glasses (more precisely: corrective glasses) are optical aids that correct ametropia, such as nearsightedness or farsightedness. In addition, glasses can protect the eyes from external influences such as UV light (sunglasses) or sparks and dust (safety glasses). Read here what glasses are available, how the different types of models work and what risks and inconveniences you have to expect with glasses.

What are glasses?

Glasses consist of a frame and two lenses. The frame of the glasses rests with the so-called bridge on the nose and with two brackets on the side of the head behind the ears. Spectacle frames can be made from plastics, metals, wood and other materials such as titanium or horn. Shape and color also vary considerably – glasses are now often seen as a fashion accessory.

Eyeglass lenses are traditionally made of mineral glass. In the meantime, however, plastic has overtaken glass. Although glass is more scratch-resistant and easier to care for, it is heavier and less shatterproof than plastic.

There are different types of glasses, each with different (main) tasks. Prescription glasses (corrective glasses) are used, for example, to correct ametropia of the eye via the refractive power in the glass. This is done by means of dioptres that are matched to the wearer’s visual acuity.

eyesight

Eyesight describes the ability of the eye to see things and contours clearly. The functional principle behind it is similar to that of a camera: the eye can focus on a point by muscles stretching or compressing the lens behind the cornea (accommodation). This change in the shape of the lens is accompanied by a change in the refraction of light, i.e. the shape of the lens is adjusted so that the light passing through is refracted in the optimal way – the focused object is sharply imaged on the retina .

If the lens can no longer (sufficiently) change its shape, this process no longer works properly – the person concerned is ametropia.

diopters

Dioptres are a unit of measurement that describes the strength with which a lens refracts light. The higher the number of diopters, the more pronounced the ametropia.  

When do you need glasses?

Glasses are visual aids intended to correct ametropia in the eye:

nearsightedness (myopia)

In short-sightedness (myopia), the eyeball is too long or the refractive power of the eye is too strong. As a result, light rays entering the eye – despite the deformation of the lens to adjust the refractive power – are not focused on the retina, but in front of it. This makes distant objects appear blurry. Glasses compensate for this with so-called diverging lenses (minus lenses) .

farsightedness (hyperopia)

In the case of farsightedness (hyperopia), the eyeball is too short or the refractive power is too weak. The incident light rays are therefore not focused on the retina, but behind it. As a result, those affected see nearby objects only out of focus. Glasses with so-called converging lenses (plus lenses) are the right corrective aids here.

Astigmatism

In the case of astigmatism, the cornea – rarely the lens – is not evenly curved. Therefore one speaks of astigmatism . As a result, the incident light rays do not hit the retina in a bundle, but rather in a line. For correction, the optician uses so-called cylindrical lenses.  

As with long-sighted and short-sighted people, there are also special contact lenses as an alternative to glasses for people with astigmatism.

What types of glasses are there?

There are different types of glasses, which can be distinguished depending on the lens or purpose. There are, among other things:

  • Glasses for long-sighted, long-sighted and short-sighted people
  • Glasses for people who do not see well both in the distance and near and do not want to constantly change their glasses (bi-/trifocal and varifocal glasses)
  • Glasses for people who only need visual aids for reading, driving a car or using the computer (reading glasses/screen glasses).

In addition, there are glasses that are specially tailored to the needs of children or athletes.

children’s glasses

Children’s glasses correct – like glasses for adults – ametropia. In addition to nearsightedness, farsightedness and astigmatism, this also often includes squinting ( strabismus ) in children. In addition, children’s glasses prevent so-called weak vision (amblyopia). In weak-sightedness, visual acuity is impaired by a developmental disorder in the visual system (eye, optic nerve , brain ): The two eyes send such different images to the brain that it cannot combine the information into a uniform visual impression.

If a child crosses their eyes in the first six years of life or if it is ametropia, the brain will not receive the stimuli it needs to train and develop binocular vision without appropriate visual correction.

Signs of vision problems in children

Because children often don’t notice their vision problems themselves, you should talk to your doctor about children’s glasses if you notice one or more of the following signs in your child:

  • headache
  • rapid eye fatigue
  • frequent winking or blinking
  • Clumsiness in playing or grasping

The ophthalmologist can check your child’s vision with various age-appropriate tests. For example, the so-called cover test can be used to detect squinting in infants:

To do this, the child should first fixate on an object with both eyes. For children who cannot speak yet, this can be done with brightly colored or glowing objects. Now the doctor covers first one and then the other eye of the child with a plastic disk. If it is the healthy eye, the squinting one will give up its squinting position and snap into the fixation position (saccade), because a squinting eye fixes objects with only one eye.

Children’s glasses: what to consider when choosing

As useful as children’s glasses are for ametropia and strabismus, they can also harbor risks. One thing may be that they do not (properly) compensate for the ametropia (short-sightedness, squinting, etc.). Then there is a risk that weak vision will develop. In addition, glasses can pinch on the nose or behind the ears if the size or shape is not optimally selected.

When choosing the frame for children’s glasses, the child should also be allowed to say what they like (as long as they are not too small for it). Then they will be more willing to wear the children’s glasses consistently.

Unbreakable materials such as plastic have proven their worth for children’s glasses. Glasses for small children should also be as light as possible and not slip when playing.

sports glasses

Sports glasses are primarily used to protect the eyes from environmental influences during sports and other outdoor activities. Examples:

  • Skiing, hiking , sailing & Co.: Strong UV radiation can cloud the lens (cataract) and permanently damage the cornea and retina. This danger arises especially when snow and water reflect the light. Sports sunglasses offer protection here.
  • Swimming : Swimming goggles protect the eyes from chlorine and water and the germs they contain.
  • Cycling: If you are out and about on a racing bike or mountain bike, there is a headwind. And that can dry out the eyes because not enough tear fluid wets the conjunctiva and cornea. On the one hand, this reduces visibility and thus also safety on the bike. On the other hand, infections and inflammations up to and including scarring of the cornea can be the result. Cycling goggles protect against this – as well as against foreign bodies (such as mosquitoes or dust) penetrating the eye.

Sports glasses with prescription lenses are now available for people who wear glasses. Then the person concerned does not have to wear contact lenses under conventional sports glasses . The ametropia is corrected directly by the prescription sports glasses. There are various models for this, for example sports glasses with ground-in correction or a clip that the athlete clamps behind the glasses of normal sports glasses.

Sports glasses: What to consider when choosing

A danger with sports glasses can arise if the model does not fit the intended purpose and/or the head shape of the wearer. For example, a poorly chosen lens tint can restrict vision, a frame that is too small can let drafts into the eyes, or the lenses can fog up as soon as the athlete starts to sweat. It is therefore important to ensure that sports glasses do not impair sharp vision in any way.

Possible risks are also:

  • Pressure points on the nose or behind the ears if the sports glasses do not fit properly
  • Eye injuries when lenses and frames are not stable enough and break during sports
  • Radiation damage to the eye if the UV protection of the glasses is too low

That is why you should always choose your sports glasses depending on how they will be used later. When buying, also make sure that the sports glasses are as light and comfortable as possible to wear and have the right fit. With jerky movements, the glasses must not slip, but they must not press either. Glasses and frame should be made of a shatterproof material. The glasses should offer sufficient UV protection.

Get advice from an optician when buying sports glasses. If you need sports glasses with prescription, your optician should do an eye test with you and adjust the glasses to your individual needs.

progressive glasses

To the questions “What are progressive lenses?” could be answered flatly: A pair of glasses for all visual situations. To put it more precisely: the task and function of progressive lenses is to combine different visual solutions in one and the same lens. This allows the wearer to see sharply at different distances without having to change glasses.

In contrast to multifocal glasses such as bi- or trifocal glasses (two or three-focal lenses), in which the different visual areas are separated from each other by a recognizable line in the lens, the transition between the different visual areas is fluid with varifocal glasses. This means there are no so-called image jumps at the edges when the wearer looks up or down.

Complex structure

Glasses with varifocal lenses seamlessly correct near vision (up to 0.5 m), distance vision (from 2 m) and also for the intermediate range, so that the wearer always sees clearly. The lenses are constructed in a correspondingly complex manner: in the lower visual range of progressive lenses, the lens has a different curvature than in the areas above. Below, varifocal glasses improve close-up vision (eg for reading), above distant vision and in the intermediate range vision in the range between half a meter and two meters (eg for reading the raised display board at the train station).In addition to the normal varifocal glasses, there are also special variants for drivers or for working on the computer screen.

Types of progressive lenses

There are differences in progressive lenses. So exist:

  • Simple varifocal lenses: relatively small fields of vision, less visual comfort, longer time to get used to them
  • Universal progressive lenses: Sufficiently large fields of vision, good comfort and good tolerability
  • Individual varifocal lenses: Made-to-measure products, offer maximum visual comfort and the highest imaging quality

It doesn’t matter which type of lens you choose: In order for the smooth vision correction transition to work with varifocals, the lenses in the frame must be large enough that the surfaces for the individual vision areas are large enough. You should also be able to see well over the edges of your glasses. With progressive lenses of lesser quality, the field of vision outdoors is often blurred.

Another quality feature is the transition from local to television. With cheap glasses, it is sometimes not fluent, but abrupt.

Cost of varifocals

The price of varifocals depends on the frame and lens quality. In any case, it costs more than glasses with conventional corrective lenses, because the production of progressive lenses is much more complex.

It is not advisable to buy very cheap glasses that cost around 30 euros. Their visual ranges are usually much too small, and the transitions are bumpy. Only from around 100 to 200 euros can one speak of “high quality” with progressive lenses – with such glasses the “change of vision” succeeds smoothly and immediately, the wearer gets used to the visual aid accordingly quickly.

Disadvantages of progressive lenses

As practical as they may be, varifocals also have disadvantages. For example, gliding vision is limited to the middle lens area. If you look to the side, you sometimes have to follow your gaze with your head to stay in the correct correction zone. Accordingly, varifocal glasses are not suitable for people who also need to see sharply in the side area, for example draftsmen.

Even people who have to work overhead (e.g. car mechanics) are better off with single-vision glasses because they can look “the other way round” overhead. So you would need the area for close-up vision at the top and the one for distance vision at the bottom.

Which glasses do I need?

If you notice for the first time that your vision is deteriorating, you should see an ophthalmologist. This also applies if you suddenly see double or flashes of light. The ophthalmologist will examine you thoroughly to determine whether the ametropia can be corrected with glasses.

Both an ophthalmologist and a master optician may issue glasses on prescription. Both are qualified to measure and prescribe the required prescription glasses.

To begin with, a doctor or optician will usually check your visual acuity using typical eye charts . To do this, you sit at a certain distance from these boards and have to read numbers or letters of different sizes – with both eyes at the same time and also with each eye individually.

The specialist then uses a so-called autorefractometer to determine the objective refraction , i.e. the refractive power of your eyes, without you having to help. To do this, it projects an image onto your retina, which the autorefractometer uses to determine the additional refractive power required to focus the image.

For the subjective refraction , you look through special glasses (photoropter) where the doctor or optician swaps lenses with different refractive powers until you see sharply.

The specialist documents all examination values ​​in a glasses passport.

What are the risks of glasses?

At first you can get headaches and dizziness from your new glasses, because the brain first has to get used to the changed visual conditions. If you don’t notice any improvement, even though you wear the glasses consistently, this may be due to the incorrect prescription of the glasses. It can then be necessary and helpful to have your eyesight checked again and, if necessary, to change your glasses.

If the glasses frame does not fit properly, you can also get pressure points on your nose and/or behind your ears from glasses.

What do I have to consider when buying glasses?

Glasses improve your vision. If your vision is blurred despite glasses, an examination by an ophthalmologist or optician will clarify the situation. You may need to have your glasses adjusted. Since the eye changes with age, an eye test is also required regularly (ie every one to two years) in order to have its refractive power determined.

Although anti-reflective glasses cause additional costs, they prevent annoying reflections and increase safety on the road or at work.

Special glasses for PC or screen work are required when normal glasses restrict vision or cause problems (such as headaches).

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