In today’s scenario, you must have noticed that whether the person is young or old, everyone is using contact lenses to rectify vision and look great. So, the popularity of contact lenses now-a-days is obvious. There are reasons for their popularity including their use as the substitute for eyeglasses to enhance the vision by correcting the refraction errors of eyes. They just need to be placed on the cornea of the eye as a small plastic plate that helps to correct different corneal refractive errors.
About Contact Lenses
Contact lenses are sort of thin transparent plates that are well planted on the cornea of the eyes. These plates are generally made of plastic material that are well polished and mould. These planted plates are well designed to fit the eye lenses of the cornea to correct various corneal errors, commonly known as refractive errors of the eyes. Some of the corneal errors that are eradicated by the contact lenses are myopia, hyperopia, cylindrical errors, astigmatism and presbyopia. They eradicate these errors similarly as normal eyeglasses do. Eyeglasses work as external aid to correct these errors whereas contact lenses work as an internal aid. Contact lenses help the light rays coming to the retina to focus exactly to form a correct image of the object and let the eyes to see it clearly.
Apart from correcting the above said corneal errors, contact lenses are also used as correcting aid for some other sort of errors such as colour scarcity that is also known as color blindness.
Types of Contact Lenses
Depending upon different factors, there are various kinds of contact lenses that are being used to correct the refraction errors of the eyes. The major factors that categorize contact lenses are their way of functioning, material of the lenses, the wearing plan and the replacement plan of the contact lenses.
Contact lenses that are designed according to their functional features are commonly known as corrective contact lenses. These kinds of lenses correct different refractive errors of eyes. Contact lenses are categorized differently according to various kinds of errors. There are various kinds of refraction errors such as myopia, hyperopia, cylindrical errors, astigmatism, presbyopia and more. For the correction of each of these refraction errors, there are different contact lenses.
The reason behind this is that the contact lenses bend the light rays in different directions according to their structure. Some of them bend the light rays vertically and some of them bend horizontally and others bend in various directions according to the structure of their plane.
For example, spherical contact lenses bend light rays constantly in various directions. Generally, spherical contact lenses are used to correct myopia and hyperopia. Toric contact lenses focus the light rays well in horizontal direction, in comparison to vertical direction due to the specific structure of their planes. Since, for the correction of astigmatism refraction error light rays needs to be bent in horizontal direction instead of vertical direction, the toric lenses are used to correct this error. Not only toric lenses but few spherical stiff lenses are also used for the correction of same kind of refraction error.
Two different kinds of approaches are used by the designers to design contact lenses for the correction of presbyopia refraction. Depending on different kinds of approaches used for designing contact lenses the type of lenses differ accordingly. These two different kinds of lenses are multifocal contact lenses and mono vision lenses that correct the presbyopia refraction. Multifocal contact lenses are designed in such a way that they have more than one focal point. Generally, they are similar in structure to the bifocal lenses that have two focal points. The lenses that have one focal point are known as mono vision lens.
For the correction of colour blindness, certain contact lenses are used such as X-chrome and Chroma Gen lenses. Though X-chrome lenses don’t have the capability to eradicate colour blindness totally from the patient’s eyes, but still they help the user to be able to differentiate between the different kinds of colours. Chroma Gen lenses eradicates the error of colour blindness up to an extent as they have certain limitations. They are not much helpful in differentiating the colour in dark or night time.
Cosmetic contact lenses are especially designed to complement your eyes with the help of attractive colours. These types of contact lenses are generally used by celebrities in film and entertainment. But, nowadays even common people have started using cosmetic lenses to increase the beauty of their eyes. Sclera lens is type of cosmetic contact lens that is used in today’s scenario. There might be certain problems while using cosmetic contact lenses without having any proper instructions from eye doctor prior to their use.
Therapeutic or remedial Contact lenses are those lenses that are especially designed in such a way that they have the property to work as a remedy for the infected eyes. There are certain infections that cause eyes to be unhealthy. Some of the common infections are corneal abrasions and erosion, dry eyes, corneal edema, anterior corneal dystrophy, neurotrophic keratoconjunctivitis. Patients that have these kinds of infections are advised to wear remedial contact lenses.
Material of the lenses used during their manufacturing also differentiates them from each other. There are essentially three types of lenses according to the property of the material used during the construction of the lenses. These three types are rigid, soft and hybrid lenses.
Rigid lenses are generally made of polymethyl methacrylate (PMMA) also known as Perspex/Plexiglas. Rigid lenses are also known as hard lenses as they are generally made up of those materials that are hard in nature. Rigid lenses are not always favourable in nature as they also have some drawbacks. The most common drawback that they have is that they don’t permit oxygen to pass from the cornea without any interruption. Interrupted supply of oxygen can lead to severe problems and make your eyes unhealthy. Earlier, certain conventional oxygen-permeable lenses were manufactured and they were commonly known as rigid gas permeable or ‘RGP’ lenses. Sometimes rigid lenses are also used for the correction of corneal error and help the cornea to restore their normal shape. For the correction of astigmatism refraction error, spherical rigid contact lenses are used. They are designed to form a new refraction surface and with the help of this refraction surface cornea is able to restore its normal shape and lets the user to see clearly by eradicating the error of astigmatism. Rigid lenses are a little different from spherical lenses. This difference is due to the reason that one or both planes of the lenses can work as a solution to toric errors. Rigid lenses can also be used for the solution of a corneal error known as keratoconus. Patients having corneal irregularity of keratoconus generally use normal eyeglasses to eradicate this error, but they don’t work better in comparison to rigid lenses and that is the reason why rigid lenses are used. Being less chemically inactive is an added advantage to the rigid lenses in comparison to the soft lenses. They can be used to be worn in different kinds of environments due to this property. While soft contact lenses can only be used in soft environments. Thus, we can say that rigid gas permeable or RGP lenses are finer enough to suite well with your eyes but still they have some of the drawbacks that need to be kept in mind while using them.
Soft lenses need less time in comparison to hard lenses to adapt to your eyes. Earlier, a special kind of lenses were used as soft lenses that were hydrogel lenses but now some of the polymers of the soft lenses are achieving the capability to pass oxygen through them. So, these are the reason why most of the people are using soft lenses these days. Though hydrogel lenses have lots of positive features but still they have some of the problems that can cause trouble. Some of the negative features with soft lenses are as, they might be slightly harder so they can have similar problems that we have in case of hard or rigid lenses.
If there is a combination of soft and hard lenses for a new lens then this newly formed lens is known as hybrid lens. Now, the question arises that why hybrid lenses are called so. This is due to the reason that they have combined properties of hard as well as soft lenses. The structure of the hybrid lens is somewhat different from the normal contact lenses. These hybrid lenses are designed in such a way that they have the center that is known as rigid center and apart from this center they also have a skirt that is soft in nature. For the formation of hybrid lenses, a special kind of technique is used and this technique is known as piggybacking. In this technique, hard and soft lenses are placed in such a way that they form a piggybacking structure in which there are two lenses backed up on each other in such way that rigid lens is backed on the surface of a soft lens. Rigid lens is smaller in size and the soft lens is larger in size. Both the lenses have different functions, the rigid lens helps to correct the vision and the soft lens helps in proving comfort to the wearer’s eye.
Schedule of wearing and replacing differs according to the time of wearing the lenses. Some lenses are meant for daily wear, some for extended wear and some for continuous wear.
The lenses that can be worn for a day only during the day time and must be removed before sleeping are known as daily wear lenses. Daily wear lenses are also known as daily disposable contact lenses as they are meant to be worn just for a day and are advised to be removed or disposed after a day’s use, before going to sleep. Extended wear contact lenses are meant to be worn continuously throughout the day and even in night, while sleeping too. The designing of the extended wear contact lens is in such a way that they can be easily worn for six consecutive nights and after wearing them for six nights and days they are advised to be removed and replaced with the new one. Modern extended wear contact lenses are being designed in such a way that they can be worn up to 30 nights continuously without replacing them from the new one. After 30 nights, they are advised to be removed as they can cause certain problems if the user is continuously wearing them. So, it is advised to replace the contact lenses after their expiry date as there may be certain complications that can lead to unhealthy eyes. Modern extended wear contact lenses are made up of special kind of materials such as silicone hydrogels. Due to the properties of silicone hydrogel, extended wear contact lenses are generally high in oxygen permeability. With the help of this property, the user can use these lenses for the whole night, even while sleeping. After entering into eyes, oxygen dissolves in the tears and further they are able to pass to the cornea, but while the user is sleeping, there are some problems in passing oxygen through the cornea at the back side of the eyelid. Modern extended wear contact lenses are able to supply oxygen through the cornea of the eyes whereas normal contact lenses don’t do that. The reason behind that why the modern contact lenses are able to pass oxygen through is that they have silicone hydrogel in them. Modern extended wear contact lenses are able to supply oxygen 5-6 times more in comparison to the normal soft contact lenses. This helps the eyes of the user to be healthy and comfortable even during sleeping.
According to the replacement program, first kind of contact lenses is single use contact lenses that are generally thrown away after using them just for one day. This is due to the fact that they can’t retain their properties after one day of usage and that is why repeated uses are not preferable for these kinds of lenses. The lenses that are advised to be replaced after a single use generally are thin and light in weight, to provide comfort to the eyes. Single use lenses are usually worn by those patients who wear contact lenses rarely just for some occasions. Apart from single use, there are other types of disposable contact lenses according to their replacement schedule and these contact lenses are those that need to be replaced after usage of two-three weeks. The third kind of lenses are called annual lenses as they can be worn up to a year and they should be replaced after using them for one year. These kinds of lenses have long life in comparison to earlier discussed disposable contact lenses. Apart from annual lenses, there are certain lenses that can last up to 5-10 years and can be used for several years without any replacement. These types of lenses are rich in gas permeability and are able to pass oxygen easily through cornea. The replacement schedule of the lenses differ according to the manufacturing process of the lenses and not the material of the lenses as generally these lenses are manufactured with the help of similar kind of materials. So, different manufacturing processes decide that the lens is daily disposable or it is the one that is to be disposed after wearing them for two-three weeks.
There are different kinds of manufacturing processes that are used by the manufacturers. Manufacturer’s produce rigid contact lenses only after getting specific directions from the user as these specifications differ from person to person. They need to be manufactured only according to the directions so to not cause any trouble to wearer’s eye and to make them feel comfortable while wearing these lenses. Different types of manufacturing process are spin-cast, diamond turning and molding method.
The lenses that are manufactured using spin-cast method are known as spin-cast lenses. The lenses manufactured with the help of this process are generally soft lenses. In spin-cast manufacturing method, liquid silicone revolves in a pattern at a very high speed so and that leads to the formation of soft lenses.
The lenses that are manufactured using diamond turning method are known as diamond turning contact lenses. Diamond turning contact method is a method that includes cutting and polishing of lenses with the help of lathe machine known as CNC lathe machine.
Initially in this method, a cylinder shaped disk holds the chops of the lathe machine. This lathe machine has diamond as the cutting equipment that is of industrial-category. This lathe machine has very high RPM that is somewhat around 6000. It cuts the cylindrical disk and eliminates the desirable amount of mater from the disk for the formation of the lens. After cutting the front surface of the disk, the other surface or the concave surface of the lens is polished. Polishing is done with a special kind of rough paste such as oil. A high speed truing ball that is made of polyester cotton is used for polishing the lenses. After polishing the concave surface of the lens is turned and another surface is cut and polished using the same process. Generally, the hard or the rigid lenses are used to shape with the help of this process. While shaping, the softer lenses there is a little difference in cutting the surface of the lens.
At last, the lenses that are manufactured using molding method are known as molding contact lenses. During the manufacturing of these lenses revolving moulds are used. A liquid is poured into the revolving moulds and this liquid gets the shape of the mould due to the centrifugal forces. Slight differences can be seen in the manufacturing processes that differ from manufacturer to manufacturer.
Care of Contacts in the Frigid Winters
Dry air during winters can harm your eyes and it could be a more complicated case if you are wearing contact lenses. That is why contact lenses should have wet ability to provide comfort to the eyes and they need some care also. That is why it is advised that lenses should be of good quality so that they can tackle the situation during winters.
If you want to keep your eyes healthy during frigid winters then you can take certain steps as a caution. You can change the contact lenses regularly according to the comfort of your eyes and the life of the lenses. You are also advised to visit the optometrist and have a regular eye check up during winter if you are feeling any problem with your eyes or contact lenses. You can also use a humidifier to restore the moisture of your room that is generally removed by the room heaters. Last but not the least, there is also a solution to the problem that you can use sunglasses to protect eyes and contact lenses.
Why is Lenskart the Best Place to Buy Contacts?
If you are looking for contact lenses then you are advised to go to lenskart.com and buy lenses online as this site has some of the well trusted best sellers of contact lenses that are selling contact lenses in India at affordable rates just according to the budget of customers. Some of the trusted brands that you will find at lenskart.com are Johnson & Johnson, Ciba Vision, Bausch & Lomb, Cooper Vision, Aryan, Acme Yearly Toric, Celebrations, Silk Lens, Fresh Kon, Biomedics and Glamour Eye and many more trusted brands of the world. These brands provide lenses with quality and class. So, you can have a nice online shopping experience with this website and have a correct pair of contact lenses for your eyes to enhance your vision.