How to insert your lenses
Removing the lens
Look up. With middle finger, hold down lower lid. Use forefinger to slide lens to lower part of eye. Pinch lens with thumb and forefinger and remove without excessively folding the lens.
Contact lenses are held in place by the tears in the eye between the lens and the front of the eye. Most contact lenses are worn on a daily basis and they should not be worn overnight. In some cases your optician may advise you that it is safe to wear your lenses when sleeping but check if you are not sure.
There are different types of lenses available for different eye problems, but they generally fall into two categories of hard and soft lenses. Almost anyone can wear contact lenses although special care is needed for children and older people. Contact lenses can treat short sightedness and long sightedness. There are also lenses available for astigmatism and presbyopia.
Types of Contact Lenses
After an eye examination, which includes checking your eyes are suitable for contact lenses as well as eye problems and the early signs of eye disease, your optician will fit the lenses. They will check that your tears are a good quality to ensure that the lenses are kept lubricated. They will also measure the size of your cornea, the pupil and the position of your eyelids to ensure the correct size lenses are fitted.
Soft Contact Lenses
Soft lenses are made from oxygen permeable plastics which become pliable during manufacturing. They contain between 30 and 40 per cent water and are very comfortable to wear, as well as being easy to fit.
Astigmatism, where the shape of the cornea causes distorted eyesight, can be treated with ‘toric’ contact lenses. Bifocal contact lenses are used to treat presbyopia, when a person has difficulty seeing close up particularly when reading. This condition was traditionally treated by wearing reading glasses for close up tasks but now bifocals ensure the person can see objects in the distance and as well as for reading.
Hard Contact Lenses
When contact lenses were first developed they were hard lenses. These lenses didn’t allow for oxygen to pass through the lens to the cornea. As they needed to be very small to leave the cornea uncovered as much as possible, they could easily fall out especially when blinking. Although these are still available for certain specialist needs they have largely been replaced by rigid gas permeable lenses.
Rigid Gas Permeable (RGP)
These lenses combine the functions of both hard and soft lenses. These are firmer than soft lenses but are made of oxygen permeable plastic. RGP lenses usually last longer than soft lenses and are very hard-wearing. Some prefer to wear these lenses as they are easier to handle than soft lenses. People with a high level of astigmatism are often prescribed RGP lenses. Once a person has got used to the lenses they are generally just as comfortable to wear as soft lenses.
Extended Wear Contact Lenses
Extended wear contact lenses are available for overnight or continuous wear ranging from one to six nights or up to 30 days. Extended wear contact lenses are usually soft contact lenses. They are made of flexible plastics that allow oxygen to pass through to the cornea. There are also a very few rigid gas permeable lenses that are designed and approved for overnight wear. Length of continuous wear depends on lens type and your eye care professional’s evaluation of your tolerance for overnight wear. It’s important for the eyes to have a rest without lenses for at least one night following each scheduled removal.
Disposable (Replacement Schedule) Contact Lenses
The majority of soft contact lens wearers are prescribed some type of frequent replacement schedule. “Disposable,” as defined by the FDA, means used once and discarded. With a true daily wear disposable schedule, a brand new pair of lenses is used each day.
Some soft contact lenses are referred to as “disposable” by contact lens sellers, but actually, they are for frequent/planned replacement. With extended wear lenses, the lenses may be worn continuously for the prescribed wearing period (for example, 7 days to 30 days) and then thrown away. When you remove your lenses, make sure to clean and disinfect them properly before reinserting.
Specialized Uses of Contact lenses
Conventional contact lenses correct vision in the same way that glasses do, only they are in contact with the eye. Two types of lenses that serve a different purpose are orthokeratology lenses and decorative (plano) lenses.
Orthokeratology, or Ortho-K, is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the curvature of the cornea to temporarily improve the eye’s ability to focus on objects. This procedure is primarily used for the correction of myopia (nearsightedness).
Overnight Ortho-K lenses are the most common type of Ortho-K. There are some Ortho-K lenses that are prescribed only for daytime wear. Overnight Ortho-K lenses are commonly prescribed to be worn while sleeping for at least eight hours each night. They are removed upon awakening and not worn during the day. Some people can go all day without their glasses or contact lenses. Others will find that their vision correction will wear off during the day.
The vision correction effect is temporary. If Ortho-K is discontinued, the corneas will return to their original curvature and the eye to its original amount of nearsightedness. Ortho-K lenses must continue to be worn every night or on some other prescribed maintenance schedule in order to maintain the treatment effect. Your eye care professional will determine the best maintenance schedule for you.
Soft lenses have numbers, are round shaped,cylindrical, minus(-) and plus(+), combined and can have colors. Lenses are daily,monthly,yearly but they are not so prefered. Most used are daily and monthly,for big numbers there are 6-months lenses too.
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” daily material (polymacon) by the United States FDA in 1971. Soft lenses are usually comfortable shortly after insertion, while rigid lenses require a period of adaptation before full comfort is achieved. The biggest improvements to soft lens polymers have been increasing oxygen permeability, lens wetability, and overall comfort.
In 1998, 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. Because silicone allows more oxygen permeability than water, the oxygen permeability of silicone hydrogels is not tied to the water content of the lens. Lenses have now been developed with so much oxygen permeability that they are approved for overnight wear (extended wear). Lenses approved for daily wear are also available in silicone hydrogel materials.
Disadvantages of silicone hydrogels are that they are slightly stiffer and the lens surface can be hydrophobic, and thus, less “wettable.” These factors can influence the comfort of the lens. New manufacturing techniques and changes to multipurpose solutions have minimized these effects. A surface modification processes called plasma coating alters the hydrophobic nature of the lens surface. Another technique incorporates internal rewetting agents to make the lens surface hydrophilic. A third process uses longer backbone polymer chains that results in less cross linking and increased wetting without surface alterations or additive agents.
Glass lenses were never comfortable enough to gain widespread popularity. The first lenses to do so were lenses made from polymethyl methacrylate (PMMA or Perspex/Plexiglas). PMMA lenses are commonly referred to as “hard” lenses. A disadvantage of these lenses is that they do not allow oxygen to pass through to the cornea, which can cause a number of adverse clinical events.
Starting in the late 1970s, improved rigid materials which were oxygen-permeable were developed. Lenses made from these materials are called rigid gas permeable or ‘RGP’ lenses.
A rigid lens is able to replace the natural shape of the cornea with a new refracting surface. This means that a spherical rigid contact lens can correct for astigmatism. Rigid lenses can also be made as a front-toric, back-toric, or bitoric. This is different from a spherical lens in that one or both surfaces of the lens deliver a toric correction. Rigid lenses can also correct for corneal irregularities, such as keratoconus. In most cases, patients with keratoconus see better through rigid contact lenses than through glasses. Rigid lenses are more chemically inert, allowing them to be worn in more challenging environments than soft lenses.
A cosmetic contact lens is designed to change the appearance of the eye. These lenses may also correct refractive error. Although many brands of contact lenses tried to make them easier to handle, cosmetic lenses worn to change the color of the eye are far less common, accounting for only 3% of contact lens fits in 2004.
In the United States, the Food and Drug Administration frequently calls non-corrective cosmetic contact lenses decorative contact lenses. As with any contact lens, cosmetic lenses carry risks of mild and serious complications, including ocular redness, irritation, and infection.
A new trend in Japan, South Korea and China is the circle contact lens. Circle lenses extend the appearance of the iris onto the sclera by having a dark tinted area surrounding the iris. The result is the appearance of a bigger, wider iris, a look reminiscent of dolls’ eyes.
Cosmetic lenses can have more direct medical applications. For example, some lenses can restore the appearance and, to some extent the function, of a damaged or missing iris.
Rigid lenses can also correct for corneal irregularities, such as keratoconus. In most cases, patients with keratoconus see better through rigid contact lenses than through glasses. Rigid lenses are more chemically inert, allowing them to be worn in more challenging environments than soft lenses.
Until about 10 years ago for the treatment of keratoconus treatment method was used only with strong contact lenses.
But, in this day a new method is introduced, effective for the treatment of this disease. This is fizioenzimatic stabilization method of keratoconus