strong>Correcting Vision With Contact Lenses

Eyeglasses are great for some people. Laser surgery works for many. But millions now enjoy the comfort, ease of use and sharp optics given by contemporary contact lenses.

Because of the way the eye and visual system work, it’s relatively straightforward today to design contact lenses that correct most vision problems. Manufacturing techniques have been raised to a high art and most of the research now goes into finding materials for longer wear or less likelihood of eye health problems.

That makes choosing a contact lens a snap today. A modern, professional eye exam allows for extremely accurate measurement of the eye and vision correction needs. The result is a prescription that fits you perfectly in any of dozens of designs and types you might want.

Choices run the gamut.

Soft contact lenses have been in use for a generation now and they continue to be the choice of millions. Virtually gone are the hard, glass contacts of yesteryear. Today’s soft lenses come in disposable, extended wear and many other options, including different types of tinting or coloring. Some tints are only meant to make the contact easy to see and handle and hard to lose. Others are intended to shift or change entirely your eye color.

But firmer lenses are still desired by or needed by many. RGP (rigid gas permeable) types are the most common here. Midway between a hard lens and a soft lens, they allow considerable oxygen through the lens to optimize eye health. Their extra firmness makes them a good choice for those with mild astigmatisms or who desire extra long life in a contact lens.

Toric contact lenses, particularly the prosite type, are useful for those with more pronounced astigmatisms. They’re also a good choice for those who want a multifocal lens, such as bifocals or progressives.

Whichever type of contact lens you get, they will generally be comfortable and provide excellent vision, if cared for and used correctly. That means cleaning them when needed, inserting and removing them according to the manufacturer’s and your doctor’s guidance. It also means using them the right way, not trying to treat daily contacts like extended wear, for example.

But, even lenses that are designed and used perfectly can occasionally cause complications. Dry eye, blurred vision, discomfort and other issues do happen to a small percentage of contact lens users. In some cases, conjunctivitis, corneal abrasions and other eye health issues are possible. When they happen, remove the contacts and consult your physician immediately. In most cases, the problem can be cleared up quickly and you can resume wearing your contacts soon.

Get a careful exam, buy from reputable dealers and use your contacts the way they were meant to be worn and you can enjoy years of perfect vision.

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strong>Contact Lenses - Material and Types

What your contact lenses are made of affects how they wear in many senses of the word, including how long they last, your comfort and their health impact. For many years contact lenses were made of glass. Today, fewer than 1% are, with the other 99% made from various types of plastic. The choices are predominantly some type of PMMA (polymethyl methacrylate), polycarbonate or silicon hydroxy gel.

Hard contact lenses introduced in the 1960s are made of PMMA and don’t allow oxygen to move directly through the lens, but some air does reach under it anyway. When a person blinks the lens moves slightly and some air diffuses through the tear solution that covers the eyeball.

Soft contact lenses, first introduced in 1971, were made of a polyacrylamide containing nitrogen (hydroxyethyl methacrylate or HEMA) which made them what is called ‘hydrophilic’. This ability to absorb water makes them flexible, and therefore more comfortable. At the same time, they are slightly more permeable to air than their older cousins.

RGP (Rigid Gas Permeable) lenses are midway between a truly hard lens, like glass or PMMA, and a soft lens. They combine PMMA with silicone and fluoropolymers that allow air to get to the eye. That increases your comfort and reduces the odds of health problems due to long-term wear.

Extended wear lenses, which come in anywhere from 2-day to 7-day to even 30-day use models, are made of silicon hydroxy gel. That material allows up to seven times the amount of oxygen to pass through the lens, making it possible to wear them longer than others.

Disposable contact lenses, first introduced in 1987, have now become extremely popular. They can be worn daily for a week or two and removing them every night is an option. Most are designed to be worn continuously then simply thrown away. Made from a combination of a polymer called etafilcon (42%) and water (58%), they’re very thin, flexible and have excellent gas permeability.

Disposables are especially popular among sports enthusiasts because of the fact that they fit close to the eye, making them very difficult to dislodge. They’re also very comfortable, so they can be easily ignored during activity. However, many don’t offer quite the level of crystal clear vision as other types, so they’re not suitable for everyone. Also, they don’t correct some vision problems as well as other types, which limits their use for some.

Apart from the choice of material and wear characteristics, there are several options today in contact lenses that simply didn’t exist 20 years ago.

Single vision lenses are like a pair of glasses worn close to the eye. They were once the only choice. Today, bifocals in contact lenses are possible. Even multifocal or progressive lenses are an option. These help compensate for presbyopia, a type of farsightedness that affects nearly everyone as they age, typically beginning in the mid-40s.

Investigate your options with your eye care professional and you’ll soon find a pair of contact lenses just right for you and your lifestyle.

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strong>How Contact Lenses Work

A clear, relatively hard mound of tissue called the cornea sits in front of the pupil of the eye. Behind the pupil is the lens that focuses light onto the retina, which creates reactions that stimulate the optic nerve to send signals to the visual cortex in the brain. That, in a nutshell, is what makes sight possible. But along the way several things can go wrong.

With age (usually) or disease, or simply because of genetics, the shape of the lens and eyeball can and do become distorted. That distortion also affects the shape of the cornea. The change in shape causes the light rays to focus in front of the retina, behind it, or to be scattered in several directions.

In the first case, the result is nearsightedness or myopia. That is the ability to see things near, but far things appear out of focus. Reading a book is easy, reading road signs while driving can be difficult or impossible without contact lenses or glasses.

When the rays would focus at a point behind the retina the effect is to produce farsightedness, also called hyperopia. Farsightedness is the ability to see things sharply that are (relatively) far away, but things up close look blurry. Reading road signs is easy, reading text on your computer without contact lenses or glasses becomes impossible.

The third case is a little different from either of the other two. In this instance, the eyeball can be misshapen or out of round, making the cornea and lens an improper shape. That produces a condition called astigmatism, the effect of which is to make images appear blurry whether near or far. That double-whammy is one of the reasons that, until recently, it was difficult to produce contact lenses or use laser eye surgery to correct this.

But the solution is (today) straightforward. Insert another lens between the light rays and the human eye’s lens. That works like a camera, which has multiple pieces of glass that can work together to focus the rays onto the film. In this case the ‘film’ is the retina. For centuries, this was done by using glasses, today, contact lenses offer an option enjoyed by millions.

The extra lenses (the contact lenses) ‘float’ on a thin layer of tear-like moisture over the cornea. Because of liquid surface tension and the shape of the eye - carefully matched by shaping the contact lens just right - the lenses can stay on and stay in place.

In short, in technical language, they change the refractive angle of the light. Refract is just a fancy word meaning ‘to bend’. That’s exactly what the lenses do. They bend the light a little bit. It’s bent a little more by the cornea, lens and fluid in the eye and - when everything is adjusted just right - the light is focused sharply onto the retina. The net result is to provide the type of array the visual cortex can correctly process as ‘car’ or ‘baby’ or whatever you happen to be looking at.

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