all about: contact lenses and how to choose them - water absorbent polymer manufacturers

by:Demi     2019-09-07
all about: contact lenses and how to choose them  -  water absorbent polymer manufacturers
Nadine bozjan
1977 this is a digital version of an article from The Times Print Archive, before it starts online in 1996.
To keep these articles as they appear initially, the Times will not change, edit, or update them.
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What is transparent, plastic, about the size of the fingernail, and it can stop playing when the basketball game loses?
This is contact lenses, and over the last 30 years it has significantly increased the way to treat eye defects and enabled patients to hide their need for visual assistance.
In fact, the idea of applying a small disk to the surface of the eye is not new --
Da Vinci is considered the most primitive concept.
But in 1887, after a Swiss eye doctor opened a glass shell for a patient with eyelid cancer, it became dormant for centuries.
Now, almost to make up for the lost time, the speed of making improvements and innovations so fast that the contact lenses 10 years ago were outdated and developed in the foreseeable future, such as sleep and a lens that can be worn once in a few months.
Currently, there are two basic types of lenseshard and soft—
Approved by the Food and Drug Administration, the authority has strict control over the industry.
The third product, the breathable lens, is currently in the research stage.
The main difference between advertising these three lenses is that they give the eyes a healthy nutrition.
Because the surface of the cornea does not contain blood vessels, it depends on the flow of tears.
Get oxygen and release carbon dioxide.
The design of the hard lens can meet this critical requirement by curvature or cutting, thus exposing a portion of the cornea.
The soft lens is hydrophilic or absorbent, so it keeps the eyes bathed in the liquid.
Oxygen reaches the cornea in two ways: directly through the lens, it is discharged from the tears under the lens, although it is more comfortable than the hand mirror.
The third is hard but breathable, which means that oxygen can pass through the material.
Each variety has its advantages and disadvantages, and the selection is based on a range of factors.
Hard lenses are often considered to have higher vision. Dr. Robert A.
Koetting, chairman of contact lenses for the American Society of optometrists, is in St.
Louis said, "the hard lens provides better optical quality than the soft lens.
They are firm and can be polished to good standards.
Soft bending, the quality of optical properties is not the same.
Other experts say the difference is so small that it makes almost no sense.
Hard lenses can correct a wider range of defects at present.
For example, most cases of astigmatism can only be remedied by hard changes.
The soft lens adapts to the irregular shape of the cornea and is not usually corrected.
In addition, only hard lenses can now be colored for sensitivity and beauty purposes.
But with more manufacturers leading the government, experts expect soft lenses to catch up in all areas.
The AdvertisementHard lens is made of a plastic called polynail grease, which is usually easier to care for, and only needs to be soaked overnight in a special solution, rinsed in the morning, it is more durable and at a lower cost.
However, despite the progress made, they still need a period of adjustment, and the soft lens is unnecessary. Dr. Morton D.
Sarver, professor of optometry and head of contact lens services at the University of California, Berkeley optometry College, said, "they were not very comfortable at first, but discomfort should not be painful or unbearable.
The doctor told the patient that he would get used to it, which was a bad suggestion.
Patients should wear the damaged period of the lens in a gradually increasing period of time should take two to three weeks to achieve 14 hours of tolerance.
"Soft lenses, F must be obtained. D. A. , were first O. K.
Made in 1971.
A license was issued to Bausch & Lomb.
Another permit was not issued until 1974.
Even today, only four manufacturers have approved Universal soft lenses.
But it is expected that about six companies will be approved in the near future.
The biggest attraction of soft lenses made of plastic polymers is poly (
2 ethyl acetate)
It's a more comfortable argument.
Some also say that it provides a wider view because it tends to be larger than a hard lens, overlapping in the sciera or white part of the eye.
Because it shapes the natural curve of the eye itself, dust and dirt particles are unlikely to be trapped under it.
"There are very few failures of soft lenses," Dr. Lawrence S.
Forgacs says his optometry practice here is limited to contact lenses and low-vision treatments.
"People prefer them because they are more comfortable during the day, during the day and at night, and want the path with the least resistance most.
In addition, the soft lens makes the wearer more relaxed in use. Dr. Richard H.
Keates, an eye professor at Ohio State University School of Medicine, said, "because there is no adaptability, it is easier to wear one day than three days.
Perfect for those wearing contact lenses on Saturday night.
"On the other hand, they deteriorate faster than the hard version and are easier to puncture and tear, and so far they require more sophisticated disinfection procedures.
October, F. D. A.
A set of three cleaning solutions has been approved, one for cleaning, one for soaking and one for flushing, but before that it requires lenses 1:1 :.
Boil in a dedicated heating device every night to prevent the growth of potentially harmful microorganisms in the soaking solution.
For those who are willing to wear lenses on a research basis, there is an option to combine the properties of hard lenses and soft lenses, which means more frequent inspections.
The well-known breathable lenses are made of a plastic called cellulose acetate. 1.
1 Paul T said that although it does not absorb water, it does bend.
Russo, president, ynpark, L. Rynco scienceI.
Pioneer in the lens.
Although some professionals predict that it will become a major competitor in the market when it is approved by F. D. A.
Not everyone can be sure of its benefits.
"Its true value has not yet been determined . "Keates said.
He asked the layman to explain the technical difference between glasses and contact lenses. G.
Peter Halberg, new chairman of the ophthamolists contact lenses Association, said, "glasses change light to adapt to defects before reaching the eyes.
Contact lenses combine the light inside the eye, and by placing a new surface in the corner, they should be combined.
They are artificial limbs floating on a layer of tears.
Like his colleagues.
Heiberg is the director of services for glaucoma and contact lenses at St.
Vincent Hospital and the New York Medical Center said that contact lenses are superior to standard glasses in addition to physiological taboos or psychological resistance, although other therapeutic uses are about to appear, patients with a cataract removed and those suffering.
Now, only contact lenses can help recover from a severe deformity known as the cornea.
With proper care and regular inspection, most doctors recommend lenses, the wearer is inspected by a professional every six months or at least every year, and the lens wearer should not be in long-term danger. Dr.
Sarver pointed out, "the cornea may be distorted with hard lenses.
It all depends on follow-up care.
Just be careful, they are as safe as we know.
The soft lens will not be used until 1971, but it should not (detrimental)
Long-term impact. ”Dr.
Koetting noted that since most contact lenses are installed between the ages of 18 and 30, in any case, when the eyes do not change much, this "leads to the wrong assumption, that is, the lens is responsible for what will happen anyway.
Although the price of contact lenses varies,
Halberg says he thinks the price of hard lenses is between $200 and $350.
The price of soft lenses is reasonable between $250 and $450.
Others say the price of soft lenses is within the range of $300.
The cost of advertising is not based on the device itself, but on a rigorous inspection, installation and tracking process.
Consumers are advised to ask in advance how long they can return to the adjustment without charging additional fees.
Three to six months is normal, but some experts include one year's service in the fees.
The expert himself is a key component of a successful prescription. As Dr.
Haiberg said: "The difference between perfection and disaster is to send line.
In the long run, lighting contact lenses can deform the eyes.
"How do patients find experts who don't cross the line, Dr.
Sarver said, "relevant consumers must seek the services of fitters who are familiar with and can use all the different lenses.
Consult those who are in good health, get advice from professional associations, and call universities with optometrists or departments of Ophthalmology.
Nevertheless, "he added," The question is similar to asking how to find the best surgeon to perform an appendix procedure.
"A version of this file was printed on page 77 of the New York edition on January 5, 1977 with the title: all about: contact lenses and how to choose them.
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