People with visual impairments have two options: opt for glasses or contact lenses. If they choose the latter, they face another alternative.
It is not a question of whether to choose a colour lens or a colourless lens. The choice is between spherical, toric and multifocal lenses. Everything depends on what kind of vision defect we have.
Lens uneven to the lens
Almost everyone can wear contact lenses, but not everyone can wear the same contact lenses. It’s not just about power, or the number of dioptres, it’s also about type. Among contact lenses there are spherical, toric and multifocal lenses. Simply put, spherical lenses are worn by people with myopia and farsightedness, toric lenses by people with astigmatism (you can find them here), while multifocal lenses are worn by people with presbyopia, commonly known as presbyopia. What kind of lenses we should wear is determined by the vision test. They should be worn by an ophthalmologist or optometrist. Currently, usually in every optical salon there is an ophthalmologist and optimist’s office, where you can not only examine your eyesight, but also choose the right lens for you.
Spherical lenses – for myopia and farsightedness
Short-sightedness and farsightedness are the most common sight defects. Short-sightedness focuses the image in front of the retina instead of on the retina, which makes it better to see only from close up, while farsightedness focuses the image behind the retina instead of on the retina, which makes it better to see only from a distance. Spherical lenses are used in both cases. Spherical lenses, otherwise known as single focal lenses, correct vision to the near or far, depending on the need. They have a PWR parameter that determines the spherical power. For short-sighted people, lenses are used that disperse the image, depending on the defect from -0.25 dioptres to -25 dioptres, while for farsighted people, lenses that focus the image are used, depending on the defect from +0.25 dioptres to +25 dioptres.
Toric lenses – for astigmatism
Astigmatism, apart from short-sightedness and farsightedness, is one of the three main defects of vision. Astigmatism results from the asymmetry of the cornea of the eye, which makes the image appear distorted and out of focus. In astigmatism, toric lenses are used. Toric lenses, apart from correction of vision to near or far, adequately refract the image. Apart from the PWR parameter, they also have the CWL cylindrical power parameter and AXE cylinder axis parameter.
Multifocal lenses – for presbyopia or presbyopia
As the name suggests, presbyopia occurs in many people when they reach a certain age. A defect in presbyopia causes corneal sclerosis. As a result, this person needs a different power to the near and a different power to the far. Multifocal lenses are used for this defect. Multifocal lenses, otherwise known as bifocal or progressive lenses, correct vision to the near and far at the same time. They have a PWR parameter, i.e. spherical power.
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