Contact lens wearers are blind to the risks

Used improperly, contact lenses can lead to infections and loss of sight.

By
August 29, 2010 01:53
Contact lenses

contact lenses 311. (photo credit: Ken Love/Akron Beacon Journal/MCT))

 
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Anyone about to undergo laser eye surgery has to sign a long form giving informed consent to the operation after reading about all possible complications. But if you want contact lenses on your corneas instead of glasses on your nose, neither the optometrist nor the ophthalmologist who prescribes them is obligated to get you to sign such a document.

In the US alone, more than 70,000 children and teens go to the emergency room each year for injuries and complications from medical devices – and contact lenses are the leading culprit, according to the first detailed national estimate, publicized a few weeks ago. About one-fourth of the problems were things like infections and eye abrasions in contact lens wearers. These are often preventable and can result from wearing contact lenses too long without cleaning them.

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While the vast majority of contact lens users manage to use them without ill effects, even the relatively small number who suffer serious infections are a lot of people, considering an estimated 125 million around the world wear them.

IN FACT, the Italian sculptor, painter, architect, scientist, engineer, musician, inventor, mathematician, geologist and anatomist of the 15th and 16th centuries, Leonard da Vinci, is credited with presenting the first ideas for contact lenses. He both described and drew them. But it took more than three centuries after his death before a German glassblower, F.E. Muller, produced the first eye covering to be seen through and tolerated and his compatriot Adolph Fick built the first successful contact lens.

Replacing early lenses made of glass, the first lenses made of polymethyl methacrylate (PMMA or Perspex/Plexiglas) were designed by William Feinbloom, which made them much more user friendly, but they were still inflexible. The first modern soft contact lenses were invented in 1961 by Czech chemist Otto Wichterle and his assistant Drahoslav Lim, who also invented the first hydrogel used to produce them. Almost four decades later, silicone hydrogels that allow much more oxygen in were developed, and these were followed by even more advances.

Special types of contacts are used in the entertainment industry to make the eye look cloudy, dilated as if taking illegal drugs or lifeless, as for horror movies. And there are some people who obtain lenses to “change” their eye color. The convex spheres can also treat vision problems – such as abnormally shaped eyeballs – that glasses cannot. One type of lenses have been shown even to make it easier for dyslexics with neurological rather than vision problems to read better, while another helps the color blind to differentiate better among colors. A rare type of contact lens is worn to cover defects such as the lack of an iris (the colored part of the eye) or damage to it. A “bandage contact lens” can be therapeutic, protecting a diseased or injured cornea from the constant rubbing of blinking eyelids. They are used to treat dry eyes, corneal ulcers, bullous keratopathy, anterior corneal dystrophy and other disorders. There are even drug-delivering contact lenses.

BUT COMFORT and personal appearance are the main reasons why the majority of people prefer contacts to glasses. When the eye’s length and refractive power are not matched, a refraction error is produced. Contacts can neutralize this and help the wearer’s eyes focus the light onto the retina properly.



Lenses can correct near- and far-sightedness, astigmatism (a common condition of blurred vision when the cornea is not perfectly spherical) and presbyopia (in which the lens in the eye becomes less able to focus on near objects as people age).

Dr. David Varssano, head of the cornea clinic at Tel Aviv Sourasky Medical Center and former chairman of the Israel Cornea Society, spends much of his time treating contact lens wearers suffering from infections and other complications.

“Some are treated in the emergency room,” he told The Jerusalem Post in an interview, “while others come to our clinic and some are even hospitalized.

Ours is one of the largest hospitals in the country; we we get many people with contact lens complications. Others are, of course, treated by ophthalmologists in the community.”

Eyeglasses, he noted, save the wearer lots of money, but that will not convince those who decide on contact lenses. While laser surgery to remove glasses has become very popular, Varssano has not noticed that this option has reduced the number of people wearing contact lenses.

Although in some parts of the world, opticians who merely sell glasses are permitted to “prescribe” and sell contact lenses, in Israel they have no license to do so; only the ophthalmologist, a physician who specializes in treating the eyes, or an optometrist who fits people with glasses and other eyewear, may do so. Contact lenses can even be ordered over the Internet, once one knows what to order, but doing so alone, without a medical address close by, is not safe. Varssano said many wearers are absolutely uninformed.

“They come to the hospital with a serious corneal infection that poses a risk to their sight and don’t understand what I’m talking about. They think contact lenses, which hug the eye, are as safe as eyeglasses! But some of them lose their sight or may need a cornea transplant.” The Sourasky ophthalmologist added that he didn’t know what optometrists tell their customers about possible dangers of lenses, but “most of them claim they knew nothing about these risks.”

In any case, those who wear lenses have to bear responsibility for their eye health. The vast majority of contacts wearers that he encounters are young people.

Children also wear contact lenses. While he has a feeling that those under 18 have relatively more infections than adults, Varssano says he has no statistics to back this up. “Relatively few people over 50 wear them; they opt for eyeglasses.”

While rigid, impermeable lenses account for over a fifth of those worn in Germany, Japan and the Netherlands, they are not common in Israel and in places like Scandinavia. Their advantage is that, because they have no pores, hey don’t absorb chemical fumes, so they would be beneficial for people whose occupation involves exposure to such harmful substances. Most of the rigid lenses used in Israel are gas-permeable substances that allow oxygen to get through to the cornea. While gas-permeable rigid lenses let in more oxygen, they are “less easy to wear. You can feel them on the eye.

People don’t like them as much as soft lenses,” said Verssano, who has been at Sourasky for 21 years.

The most important lens safety rule – besides the need to clean and disinfect them as prescribed and wash your hands with soap and water before inserting or removing your contacts – is never to leave them on while sleeping. This, said the ophthalmologist, not only reduces oxygen supply to the delicate tissue but also allows debris to accumulate and bacteria to grow on your corneas.

“Lens wearers are putting a plastic object on a very fragile part of the eye. They have to be careful.”

Although extended-wear contact lenses can be worn continuously for about a week at a time, Varssano does not recommend them.

The appearance of silicone hydrogels 11 years ago offered high permeability of oxygen, but although manufacturers initially said they can be worn overnight, in recent years they have not been approved by the health authorities for overnight use.

Like eyeglasses, noted Varssano, contact lenses can have one (single vision) or more (multifocal) focal points. But multifocal soft contact lenses are more difficult to manufacture and fit.

Ironically, in recent years there has been renewed interest in orthokeratology – the correction of myopia (nearsightedness) by deliberate overnight – temporary – flattening of the cornea, so that the wearer can see better without the lens in the eye during the day. As could have been expected, said Verssano, multiple reports of infectious bacterial keratitis following the use of such lenses have been published.

Some users of conventional lenses suffer from allergies, dryness or chronic eye infections. They may also have conjunctivitis – an acute inflammation of the conjunctiva, the outermost layer of the eye and the inner surface of the eyelids, most commonly due to an allergic reaction or an infection, But infectious bacterial keratitis, which is a potentially dangerous acute condition of the cornea itself, develops in only a few days and can be painful.

“We usually treat keratitis with antibiotics drops, since an infusion of antibiotics is less effective. But often we have to take a culture, and patients have to be under observation. One growing problem is that bacteria develop resistance to antibiotics. “We can’t solve all problems,” he concluded.

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