There are various types of lenses to correct the different visual defects that exist:
- Monofocal lenses: Monofocal lenses are those that correct nearsightedness, farsightedness or astigmatism. The entire lens has the same graduation.
- Progressive lenses: correct presbyopia. There are different graduations throughout the lens to correct the distance and near defects. The prescription is arranged in a gradual manner starting at the top of the lens with the prescription needed for far away to the middle part of the lens with the prescription for objects in the intermediate distance to the bottom of the lens where the near prescription is located to read or focus well on the cell phone.
- Bifocal lenses: correct presbyopia. In contrast with progressive lenses, they are characterized by having a line on the lens that separates the necessary distance prescription from the near one. This type of lens does not have the prescription necessary to see objects well at intermediate distances. It only has the prescription of the far and near distance separated only by a line.
- Occupational lenses: provide good near vision at 40 cm and intermediate distance where the computer is located. However, at far distances it is not valid. It is a good option for people who spend part of their time in the office in front of screens and the distances they use are not very long. It is designed for people suffering from presbyopia. They have difficulty focusing on objects and reading at a distance close to the eyes at about 40 cm.
- Photochromic lenses: they correct all the defects mentioned above. They are lenses containing particles that are activated by sunlight. When these particles are activated, the glass darkens so that it becomes a sun glass that protects against solar radiation. When the sunlight disappears, for example when we are indoors, the particles are deactivated and the crystal is no longer dark.
TYPES OF LENSES ACCORDING TO THIKNESS
Crystals can also be classified according to their thickness. It will depend on the prescription needed. If the person has a very high prescription, it will be necessary to choose a lens that is not very thick because, apart from aesthetics, thick lenses are heavier. Depending on the thickness of the lens, they can be classified numerically from 1.5 to 1.9. This number corresponds to the refractive index. The lower the number, the thicker the lens. In other words, a 1.5 index lens will be thicker than a 1.9 index lens. Lenses that are very thin (1.9) are mostly used for prescriptions that are very high such as very high myopia or very high hyperopia. Generally, lenses between 1.6 and 1.67 are used and they look good aesthetically and also because of the weight. It will also depend on the type of frame you choose. If the frame is large, it is better to use a thin lens as the lens may protrude at the edges. If the frame is small, the glass will be thinner, so there is no need to choose even thinner glass. Eye care professionals will advise you on your choice.
TYPES OF LENSES ACCORDING TO THE TREATMENT
For the greatest comfort and well-being in any situation, the lenses have a series of special treatments:
- Anti-reflective: prevents reflections outside and inside the lens, giving you a sharp, clear and beautiful image while reducing eye fatigue.
- Photochromic lenses: Corrects all the defects mentioned above. These lenses contain particles that are activated by sunlight. When these particles are activated, the glass darkens so that it becomes a sun glass that protects against solar radiation. When the sunlight disappears, e.g. when we are indoors, the particles are deactivated and the glass is no longer dark.
- UV filter: these glasses have solar filters that absorb ultraviolet radiation and protect the health of our eyes.
- Polarized: Glasses with polarized lenses are designed to filter and stop the reflection of sunlight on soft surfaces such as snow or water, allowing only useful light to pass through. This results in a light-free image with natural color and contrast.
- Screen treatment: This special treatment is intended for those who spend a lot of time indoors and are exposed to LED lights from computer screens, cell phones, televisions, computers, etc. ultraviolet light.
TYPES OF LENSES ACCORDING TO THE MATERIAL
explain the unique characteristics of each model so you can decide which one best suits your needs and preferences:
- Mineral lenses: this type of lens is made from a mixture of silicon dioxide and metal oxides such as titanium or sodium. The result is a thin, tough glass that is scratch-resistant, but heavy and easily broken. This material is suitable for both advanced and traditional prescriptions, as the size of the lens can be reduced to make it more beautiful.
- Organic lenses: this lens is made of the same polyester resin and is suitable for medium or low prescriptions. This glass is the most used material, due to its technical characteristics, as it has many advantages. They are more durable than mineral ones, adaptable to any type of frame, light and almost indestructible, so they are good for children. However, they tend to scratch faster.
- Polycarbonate lenses : this lens is impact resistant, very light and thin, so it is good. It is especially recommended for children, athletes or people who do dangerous work, the disadvantage is that the quality of vision can be improved.
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