Eyeglasses & Eye Care Community

A myriad of options of objective

The material to be left whose objective is fact has little impact on the corrective power of the objective, but he can have an significant impact on the lifestyle. You inform about the material of objective the different and made options best choice for your next pairs of glasses.

Objectives of Safety-Index:

objectives of Safety-index are made of a special plastic which refracts the light in a different way that the regular plastic objectives. With objectives of safety-index, the vision can be corrected with less material, making with the objective much thinner. Plastics are evaluated in the numbers, such as 1.50 or 1.67. More the number is high, the thinner the objective. Since they are thinner, the objectives of safety-index are also lighter, making them more comfortable to carry. It is important for patients presenting of the raised regulations, because their glasses can be returned more in an aesthetic way attractive and attractive. the materials of objective of Safety-index tend to cost the plastic objectives more than standard.

Polycarbonate objectives:

Polycarbonate objectives are made of a type of plastic which is more resistant to the shocks than the standard plastic objectives. The polycarbonate objectives are also much of thinner and lighter in the weight. They are considered a high plastic of index. The polycarbonate objectives also have integrated ultraviolet protection. Because of these properties, it is the material of objective of the choice for the objectives of the children, the objectives of sport and the objectives of safety. However, some complain that the polycarbonate objectives do not give them the vision more crunching and clearest.

Objectives of Trivex:

Trivex, also known under the name of Phoenix or trilogy, is a relatively new material which is similar to the objectives of polycarbonate but with an optical system more high-quality, and thus provides a clearer vision. Trivex is lighter in the weight than the standard plastic but not as slightly as polycarbonate. Trivex is a more rigid material, making him a better choice of the reinforcements without mounting or drill of frame. Trivex is right like resistant to the shocks which the polycarbonate and can also be prescribed for the objectives of the children, the objectives of sport and the objectives of safety.

Aspheric objectives:

An aspheric design of objective gives several advantages to the objectives of monocle. An aspheric objective has peripheral curves more punts that a regular spherical objective. This reduces the quantity which an objective can swell out of a reinforcement of monocle, reducing the optical report/ratio of the eyes, which improves the cosmetic aspect. Peripheral curves more punts also reduce the deformations which occur while looking starting from the center of the objective, making the CAP with vegetables of vision much. The aspheric objectives are also much lighter in the weight that the standard spherical objectives.

anti-r3fl chissants coatings:

the Anti-r3fl chissant coating is applied to the objectives of monocle to reduce the quantity of internal and external reflexions to an objective. This increases the quantity of light transmitted by the objective, which improves quality of the vision. the Anti-r3fl chissant coating also decreases the nondesired gleam and halations at the night. It also makes the objectives seem somewhat invisible and very slightly. While each one could draw benefit from an anti-r3fl chissant coating, it is particularly salutary for the people with raised regulations, the people who have a reduction in the vision the night, and the professions in which the cosmetic aspect is important.

Stripe-Resistant coatings:

Stripe-resistant coatings are applied to before and to the back of the objectives in the manufacturing process. Although it is important to realize that no objective is scratch-proof, this special coating makes objectives harder to stripe once dropped or rubbed against a hard surface. While the majority of the objectives are made with the stripe-resistant coating, sometimes the stripe-resistant coating of limit indicates a type of  guarantee of scratch.  The guarantee of these guarantees against scratches, ensuring the objectives will be remade if a scratch occurs. Be sure to clarify any guarantee of this nature.

Ultraviolet treatments:

The ultraviolet treatment is applied to the objectives to protect itself from the harmful sunrays UV which can accelerate the development of the cataracts and the macular degeneration. It is extremely important to protect from the eyes against the effects prejudicial of the sun. Treatment UV is easy to apply to the objectives and is often included with the purchase of the glasses.

Polarized objectives:

Polarized objectives are usually used to make sunglasses. They are most generally available in the colour gray or brown but much of other colors are available. The objectives vertically polarized decrease the luminous gleam and reflexions by blocking horizontal polarized reflected light. Polarized objectives were employed by fishermen during years to improve the business with the luminous light being reflected in addition to water and to see deeper in water.

Objectives of Photochromatic:

The objectives of Photochromatic have a special chemical coating which makes the modification to them to a colour sunk in the free space of sunlight and turn inside. The objectives of Photochromatic are large for the people who do not wish to carry a separate pair of sunglasses of regulation. It is important to identify that these objectives do not darken as well while driving a car. The windshield prevents the major part of light UV from achieving the goal.

Best glasses online shop:  GlassesShop.com

Popularity: 11% [?]

How to understand the glasses prescription

The forms of the glasses prescription are in a great variety, but the basic items are the same such as name, sex, age, occupation and so on.

The most important items are the nature of the sphere lens, the diopter, the refraction degree of the column lens, the axial position, uncorrected visual acuity of the right and left eyes, corrected visual acuity as well as the pupil distance.

Now I would like to tell you the meaning of the marks in the prescription.

OD / RE / R :  right eye
OS / LE / L : left eye
+ :  Convex lens   ( for the hypermetropia )
- :  Concave lens   （for the myopia）

After “ +” or“ –”  , the Arabic value is lens’ diopter, but what needs to pay attention to is that diopter in the prescription glasses  and the strength are not the same, a difference of 100 times between them, for instance, – 1.00D is equal to 100 degrees which we usually say;

DS :  Spherical lens （both for hyperopia and myopia ）
DC :  Cylindrical lens ( for astigmatism )

Behind DS, there is a mark “()”, representing the spherical lens “United” the following the cylindrical lens; at the back of DC, there is also a mark “×”, separating  the front degree of astigmatism from the behind the astigmatic lens axis （1～180°）;

PD :  pupil distance
For example,
Ｒ：—2.OO DS () — 2.OO DC × 90°
ＰＤ：63mm

It stands for right eye，200 degrees of myopia with 200 degrees of astigmatism, degree of astigmatism axis is 90 °, the pupil distance is 63 millimeters .

Popularity: 12% [?]

Eyeglass Prescription: Lens Strength

The values indicated in the “sphere” and “cylinder” columns of an eyeglass prescription specify the optical power of the lenses in diopters, abbreviated D. The higher the number of diopters, the more the lens refracts or bends light. A diopter is the reciprocal of the focal length in meters.

If a lens has a focal length of 1/3 meters, it is a 3 diopter lens.A +10 diopter lens, which has a focal length of 10 centimeters, would make a good magnifying glass. Eyeglass lenses are usually much weaker, because eyeglasses do not work by magnifying; they work by correcting focus.

The eye itself has a refractive power of 60 diopters.Stacking lenses combines their strength. A +1 diopter lens combined with a +2 diopter lens forms a +3 diopter system.

Lenses come in positive (plus) and negative (minus) powers. Given that a positive power lens will magnify an object and a negative power lens will reduce it, it is often possible to tell whether a lens is positive or negative by looking through it.
Positive eyeglass lenses can concentrate sunlight.

This series of pictures shows the shadow cast by a pair of 1 diopter drugstore “reading glasses” outdoors in sunlight as we hold it farther and farther away from a wall. As the distance from the wall increases, the shadow of the frame seems to thicken and the bright area in the center gets smaller and brighter. It slowly changes from being “eyeglass-shaped” to circular.

Negative lenses spread sunlight instead of concentrating it.

A negative lens combined with a positive lens removes some of its strength. A -2 lens combined with a +5 lens forms a +3 diopter system.

A -3 lens stacked on top of a +3 lens looks almost like flat glass, because the combined strength is 0.

In science textbooks, positive lenses are usually diagrammed as convex on both sides; negative lenses are usually diagrammed as concave on both sides. In a real optical system, the best optical quality is usually achieved where most rays of light are roughly normal (i.e., at a right angle) to the lens surface.

In the case of an eyeglass lens, this means that the lens should be roughly shaped like a cup with the hollow side toward the eye, so most eyeglass lenses are menisci in shape

Popularity: 14% [?]

Classifies of Contact Lenses By Wear Time

A daily wear contact lens is designed to be removed prior to sleeping. An extended wear (EW) contact lens is designed for continuous overnight wear, typically for 6 or more consecutive nights.

Newer materials, such as silicone hydrogels, allow for even longer wear periods of up to 30 consecutive nights; these longer-wear lenses are often referred to as continuous wear (CW). Generally, extended wear lenses are discarded after the specified length of time. These are increasing in popularity, due to their obvious convenience.

Extended- and continuous-wear contact lenses can be worn for such long periods of time because of their high oxygen permeability (typically 5-6 times greater than conventional soft lenses), which allows the eye to remain healthy.

Extended lens wearers may have an increased risk for corneal infections and corneal ulcers, primarily due to poor care and cleaning of the lenses, tear film instability, and bacterial stagnation.

Corneal neovascularization has historically also been a common complication of extended lens wear, though this does not appear to be a problem with silicone hydrogel extended wear.

The most common complication of extended lens use is conjunctivitis, usually allergic or giant papillary conjunctivitis (GPC), sometimes associated with a poorly fitting contact lens.

Popularity: 17% [?]

Classifies of Contact Lenses By Material

Contact lenses are classified in many different manners.

Contact lenses, other than the cosmetic variety, become almost invisible once inserted in the eyeThe first contact lenses were made of glass, which caused eye irritation, and were not wearable for extended periods of time.

But when William Feinbloom introduced lenses made from polymethyl methacrylate (PMMA or Perspex/Plexiglas), contacts became much more convenient. These PMMA lenses are commonly referred to as “hard” lenses (this term is not used for other types of contacts).

However, PMMA lenses have their own side effects: no oxygen is transmitted through the lens to the cornea, which can cause a number of adverse clinical events. In the late 1970s, and through the 1980s and 1990s, improved rigid materials ??which were also oxygen-permeable ??were developed.

Collectively, these polymers are referred to as rigid gas permeable or ‘RGP’ materials or lenses. One advantage of hard lenses is that, due to their non-porous nature, they do not absorb chemicals or fumes. The absorption of such compounds by other types of contacts can be a problem for those who are routinely exposed to painting or other chemical processes.

Rigid lenses offer a number of unique properties. In effect, the lens is able to replace the natural shape of the cornea with a new refracting surface. This means that a regular (spherical) rigid contact lens can provide good level of vision in people who have astigmatism or distorted corneal shapes as with keratoconus.

While rigid lenses have been around for about 120 years, soft lenses are a much more recent development. The principal breakthrough in soft lenses made by Otto Wichterle led to the launch of the first soft (hydrogel) lenses in some countries in the 1960s and the approval of the ‘Soflens’ material (polymacon) by the United States FDA in 1971. Soft lenses are immediately comfortable, while rigid lenses require a period of adaptation before full comfort is achieved.

The polymers from which soft lenses are manufactured improved over the next 25 years, primarily in terms of increasing the oxygen permeability by varying the ingredients making up the polymers.

A small number of hybrid rigid/soft lenses exist. An alternative technique is piggybacking of contact lenses, a smaller, rigid lens being mounted atop a larger, soft lens. This is done for a variety of clinical situations where a single lens will not provide the optical power, fitting characteristics, or comfort required.

In 1999, ’silicone hydrogels’ became available. Silicone hydrogels have both the extremely high oxygen permeability of silicone and the comfort and clinical performance of the conventional hydrogels. These lenses were initially advocated primarily for extended (overnight) wear, although more recently daily (no overnight) wear silicone hydrogels have been launched.

While it provides the oxygen permeability, the silicone also makes the lens surface highly hydrophobic and less “wettable.” This frequently results in discomfort and dryness during lens wear. In order to compensate for the hydrophobicity, hydrogels are added (hence the name “silicone hydrogels”) to make the lenses more hydrophilic.

However the lens surface may still remain hydrophobic. Hence some of the lenses undergo surface modification processes which cover the hydrophobic sites of silicone. Some other lens types incorporate internal rewetting agents to make the lens surface hydrophilic.

Popularity: 16% [?]

Introduce oIntroduce of Lens Types of Sunglasses

There are about four common types of lens including polycarbonate, glass, acrylic and unless started otherwisePolycarbonate: The most common lens material used in sunglasses today.

Offers the highest impact resistance of any lens material.

Addition, polycarbonate lenses are 10x more impact resistant than conventional plastic or glass lenses.

Polycarbonate can be mixed with many tints to produce lens shades. After injection, the material is placed in a centrifical force mechanism to adjust its optical correctness and curvature base.

Glass: Has the best optical quality and higest scratch resistance of all lens materials, although its weight should be considered. Also the material of choice for perscription sunglass lenses.

Acrylic: Unlike polycarbonate or glass, acrylic is not naturally UV protective. As a result, UV coatings are applied during the manufacturing process.

Unless stated otherwise, all sunglasses featured at The Sunglass Man feature polycarbonate lenses.

Popularity: 15% [?]