Spheric vs. Aspheric: Which lenses are better?
Daily, weekly and monthly lenses are the main distinguishing features of contact lenses. Besides, you can choose between coloured lenses, multifocal lenses and lenses specially made for people suffering from presbyopia. Not to mention the different combinations of prescriptions that are possible today. Almost any ametropia can now be corrected with the help of contact lenses.
But those are not the only differentiators. In fact, technical aspects determine whether your contact lens fits well and corrects your vision properly. Thus, the curvature of the lens plays a big role, when it comes to getting the best visual results. Read on and find out to what extent the sphere is crucial for your vision and the comfort of your eyes.
Spheric and aspheric contact lenses – modern corrections for modern ametropics
The curvature of a contact lens is distinguished by spheric and aspheric designs.
Aspheric contact lenses provide much more precise light guidance, whereas spheric contact lenses do not provide this additional advantage to such an extent.
Spheric lenses have excellent imaging properties. But when it comes to severe ametropia, aspheric surfaces perform better. This is particularly evident in the marginal areas of the lenses. From there, the light is directed to the focal point of the visual aid.
For the wearer, this not only results in a clearer and brighter image. The visual range is less restricted, as larger parts of the lens can be used for viewing.
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What are the limits of spheric lenses?
Spherical contact lens models are the most commonly used. For a long time, there were no other forms of contact lenses at all. But they are not always the best choice. The reason for this is their sometimes inadequate optical quality. They can cause aberrations that lead to blurred vision.
Opticians call this phenomenon spherical aberration because it only occurs in spherically shaped optical lenses: Not all light rays that hit the lens surface subsequently converge at the same point. The rays incidence in the area of the curved lens edge are refracted differently than those in the axis area. Thus it is not possible for the eye to focus all rays at the same time. This results in a blurred image.
Aspherical contact lenses for improved visual comfort?
To eliminate this disadvantage, we offer aspheric lenses that do not follow the spheric shape.
In comparison to spheric lenses, aspheric ones also have a curvature in order to sit optimally on the eyeball. But their edges are flattened. The flat curvature changes the optical properties of the lens. The latest manufacturing processes make it possible to produce this special shape.
The largely freely formable surface allows the avoidance or reduction of aberrations that are unavoidable with spherical lenses.
The lenses can be better adapted to the curvature required
by the eye. They deflect light rays as required by the wearer
and avoid image errors. Therefore, an optimal visual result is
Are aspheric contact lenses suitable for every contact lens wearer?
It is best to ask an ophthalmologist, if you suffer from an eye disease. He or she will determine whether your eyes are suitable for wearing contact lenses at all. Generally, ophthalmologists do not recommend wearing aspheric lenses if your hyperopia has been corrected by laser eye surgery.
The situation is different for patients with cataracts. Since the effects of spheric aberration are stronger, ophthalmologists recommend aspheric contact lenses, or spectacle lenses in this case. In addition, the type of ametropia, as well as eye diseases, play a major role. Lenses with an aspheric front are the best choice in cases of severe nearsightedness or farsightedness. People with a large pupil diameter should also use this type of lens.
Aspherical contact lenses at a glance
- Aspheric contact lenses are similar to their spheric counterparts. However, they do not have a spherically curved surface and their edges are flattened, so the image is less distorted than with spheric lenses. The vision is sharper due to better peripheral imaging.
- Aspheric contact lenses prevent the so-called spherical aberrations, i.e. the peripheral distortions caused by pupil enlargement during some activities.
- The aspheric lens design can help to increase visual acuity even in poor lighting conditions, or when driving in the dark, when working with a computer, or for sports activities that require fast focus.
- Aspheric lenses can correct low astigmatism up to –0.75, or presbyopia.
- BUT: There are individuals who do not profit from the aspheric lens surface. Their eyes depend on spherical aberrations to ensure optimal vision.
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