Vision Correction: Taking a Look at What's New
Vision correction has come a long way since the 13th century when the first
pair of spectacles was made by riveting together the handles of two magnifying
lenses. Today, surgical developments in vision correction, as well as advances
in traditional eyeglasses and contact lenses, can potentially improve a person's
vision to better than the optimal range of "20/20."
It's no surprise, then, that people dependent on glasses or contact lenses
are visiting their eye-care specialists, hoping to find a quick fix for some
age-old vision problems among the array of new techniques, products and technologies.
Learning about some of the common disorders that can threaten vision and how
the eye "sees" can help you determine the best treatment to correct
your vision. It's also important to understand the advantages, disadvantages,
and limitations that come with vision correction procedures and aids.
How the Eye Sees
Having 20/20 vision means seeing at 20 feet what a person with normal vision
sees at 20 feet. A person who has 20/40 vision can see at 20 feet what the person
with normal vision sees at 40 feet. And so on.
The eye does not actually "see" objects. Instead, it sees the light
that objects reflect. To see clearly, light striking the eye must be bent or
"refracted" through the cornea--the clear window at the front of the
eye that provides most of the focusing power. Light then travels through the
lens, where it is fine-tuned to focus properly on the nerve layer that lines
the back of the eye--the retina--and sent to the brain via the optic nerve.
The retina acts like the film in a camera, and clear vision is achieved only
if light from an object is precisely focused on it. If not, the image you see
is blurred. This is called a refractive error.
Refractive errors usually occur
in otherwise healthy eyes. They are
caused mostly by an imperfectly shaped
eyeball, cornea or lens. There are
four basic types of errors:
Myopia or nearsightedness--Close objects appear sharp but those in the
distance are blurred. The eyeball is longer than normal from front to back,
so images focus in front of the retina instead of on it.
Hyperopia or farsightedness--Distant objects can be seen clearly but
objects up close are blurred. The eyeball is shorter than normal, so images
focus behind the retina.
Astigmatism--Objects are blurred at any distance. The cornea, lens,
or both are shaped so that images aren't focused sharply on the retina.
Presbyopia or aging eye--The eye loses its ability to change focus due
to the natural aging process. This usually occurs between ages 40 and 50.
Glasses, contact lenses, and laser
eye surgery attempt to reduce refractive
errors by making light rays focus
properly on the retina.
Laser Eye Surgery--A Popular Alternative
Laser eye surgery is intended for people who want to minimize their dependency
on glasses or contact lenses. Laser surgery can provide vision correction similar
to what would be obtained with glasses or contact lenses. People under the impression
that surgery can improve their vision beyond what they can see with glasses
or contact lenses, however, likely will be disappointed.
By far, the largest increase in laser eye surgery interest recently has been
in a procedure called "laser in situ keratomileusis," popularly
known as LASIK. Advertising for this technique appears prominently on broadcast
outlets, including the Internet and in newspapers and magazines. Fortunately,
says Terrence P. O'Brien, M.D., a spokesman for the American Academy of Ophthalmology
(AAO), most surgeons and medical centers are doing a good job of educating the
public about the risks and benefits of LASIK. "But patients need to be
very well-informed in advance," he says.
LASIK permanently changes the shape of the cornea, and is performed for varying
degrees of nearsightedness, farsightedness, and astigmatism. A surgical knife,
called a microkeratome, is used to cut a flap in the cornea, leaving a hinge
at one end of the flap. The flap is then folded back to reveal the middle layer
of the cornea, called the stroma. Pulses from a computer-controlled excimer
laser vaporize a portion of the stroma and the flap is then replaced. By removing
this tissue, the shape of the central cornea is changed, and the refractive
error is reduced.
O'Brien, who is also director of refractive surgery at the Wilmer Eye Institute
at Johns Hopkins University in Baltimore, has performed over 10,000 eye surgeries.
Still, he warns that people considering LASIK need to be wary of ads that make
"Price should not be the first factor" in considering to have delicate
eye surgery, he says. "People fear blindness second only to cancer, and
just as they wouldn't consider a discount open heart operation or budget brain
surgery, they shouldn't take a chance with their eyes." The real struggle,
he says, is in training doctors. "The most advanced technology and precise
laser will give poor results if you don't have an experienced, capable surgeon."
This latest hype about LASIK's now-more-affordable advantage, coupled with
some pretty appealing results, makes surgery one of the most exciting vision
correction options available. Doctors say that LASIK gives a rapid visual recovery,
with minimal pain, and little or no post-operative discomfort. In fact, most
people who undergo LASIK, like Beth Polazzo--one of O'Brien's patients--can
see well enough to drive immediately after surgery, and usually have excellent
vision within a week.
"I had good vision immediately," says the 54-year-old Brooklyn, N.Y.,
resident, even though eventually one eye had to be retreated. "This is
the best I've seen since I was seven years old." The laser does its work
on each eye in less than a minute, and patients are typically back to work or
normal activities within three days.
While most people are pleased with the results of their surgery, O'Brien says
that, as with any medical procedure, there are risks involved. Some include:
over- or under-treatment; the inability to wear contact lenses; permanent loss
of vision; reduction in the quality of vision including the development of glare,
halos, and starbursts; difficulty with night-driving; and reduced vision in
dim lighting conditions. The risks are doubled when both eyes are treated at
the same time.
Also, LASIK is not reversible. That's why in Polazzo's case, O'Brien intentionally
undercorrected her distance eye. "We were aiming for modified monovision,"
he explains, which means that one eye would see close up while the other would
be corrected to see distances. But Polazzo experienced some regression in her
distance eye--that is, her distance vision began to worsen as she returned to
nearsightedness--some weeks following surgery. However, because of the initial
undercorrection, O'Brien was able to fix the problem.
A. Ralph Rosenthal, M.D., director of the Food and Drug Administration's division
of ophthalmic and ear, nose and throat devices in the Center for Devices and
Radiological Health, says that no one knows the long-term effects of laser eye
surgery. "We just can't know that yet," he says, so when people call
looking for a guarantee in years for the success of the procedure, "I can't
give them one."
Before undergoing LASIK, Rosenthal says people should carefully weigh the risks
and benefits based on what's important to them, and potential side effects,
including the pros and cons of having one or both eyes done on the same day.
It's also important to avoid being influenced by friends who have had LASIK
surgery or doctors who encourage patients to do so.
A second laser procedure used today as an alternative to LASIK is photorefractive
keratectomy, or PRK. Although O'Brien says that less than 5 percent of people
undergo PRK, it is still the procedure of choice for certain eye conditions.
This type of refractive surgery gently reshapes the cornea by removing microscopic
amounts of tissue from the outer surface with a cool, computer-controlled ultraviolet
beam of light. It does not, however, involve cutting. The procedure takes only
a few minutes, and patients are typically back to daily routines in five to
Clinical studies indicate that about 5 percent of PRK recipients continued
to need glasses for distance vision following the surgery, and up to 15 percent
need glasses occasionally, such as when driving. In addition, many people experienced
mild corneal haze following surgery, which is part of the normal healing process.
The haze appeared to have little or no effect on final vision, and could only
be seen by a doctor under a microscope. For about 5 percent of PRK patients,
best-corrected vision without corrective lenses was slightly worse after surgery
than before. These conditions, however, improved or disappeared in most people
in six months.
Another new, less-invasive laser procedure--indicated for temporarily reducing
hyperopia--is being aimed exclusively at people over 40. Laser thermal keratoplasty,
or LTK, involves zapping 16 spots on the outer part of the cornea to shrink
the tissue. People usually can leave 30 minutes after the procedure and resume
normal activities the following day. The advantage of LTK is that it's a "no
touch" procedure, meaning there's little chance of infection or loss of
vision. The disadvantage is that the procedure is considered temporary since
the treatment effect regresses--for many people, about half of the correction
is gone within two years. Another drawback is that people may become nearsighted
in the first six weeks, enough to require glasses for driving, and their vision
can fluctuate for weeks after surgery.
Rosenthal wants people considering laser surgery to know and carefully weigh
the pros and cons. "FDA mandated that manufacturers of all excimer lasers
make available to people a patient information booklet," he says, that
spells out this information. If the doctor fails to offer one, Rosenthal says
that you should ask for it.
Experts say that the reliability of laser vision correction is quite good in
mild to moderate levels of refractive errors. But people desperate for clear
vision need to understand the dangers. The most satisfied laser surgery patient
is one who has realistic expectations and a thorough understanding of the risks
and possible complications of refractive surgery.
Contact Lenses--More Choices
Whether you're interested in wearing contact lenses for the first time, or
are considering an upgrade for comfort and convenience, discussing the latest
innovations with your eye-care practitioner will help make your choices easier
and minimize the risks. Advances in materials for precision lenses have made
soft and rigid gas permeable contacts--the two main contact lens groups--an
option for more people. These medical devices are made of many different types
of plastic, and offer numerous options. With daily wear or extended wear (overnight)
lenses, the options include frequent- or planned-replacements, disposables,
bifocals, UV-blocking contacts, and more. There are clear, tinted, opaque, spherical
and rounded lenses. So where does someone start when deciding if contact lenses
are the right choice for vision correction, and what to choose?
Hal Balyeat, M.D., professor of ophthalmology at the University of Oklahoma's
Dean A. McGee Eye Institute, says people satisfied with their vision correction
may not need to look very far. "If you are already a satisfied contact
wearer," he says, "you may not consider other options worthwhile when
you're wearing your contacts as well as you are." Satisfied wearers typically
have no allergies and have not developed an intolerance to contact lenses. The
bottom line: If contact lenses are working for you, Balyeat says, it's hard
to justify other options, such as permanent laser alteration of otherwise healthy
Balyeat cites his wife, Marilyn, as an example. Although she was a good candidate
for the LASIK surgery, she opted for monovision contacts--one lens focuses close
up while the other lens corrects for distance vision. "At 60," she
says, "I can still read without glasses." And that, says her husband,
is the single most important factor: "If you like being able to take out
your contacts and still see up close, surgery is not a worthwhile trade-off."
Balyeat adds that many people don't realize that laser surgery, performed on
people over 40, won't let you see up close without glasses or contacts unless
you opt for monovision LASIK.
Contact lens quality continues to improve. Soft contacts contain from 25 percent
to 79 percent water, are easy to adjust to, and are more comfortable than rigid
gas permeable (RGP) lenses, thanks to their ability to conform to the eye and
absorb water. Soft lenses aren't likely to pop out or capture foreign material
such as dust underneath, as hard lenses are. Extra-thin soft lenses are available
for very sensitive eyes.
While the ability to hold water increases oxygen permeability of soft lenses,
it also makes them more fragile. And soft lenses are more likely to absorb chemicals
and residues on the wearer's hands.
RGP lenses are more durable and resistant to deposit buildup, and they generally
give clearer, crisper vision. They tend to be less expensive over the life of
the lens, but the initial cost often is higher. RGP contacts last several years,
while soft contacts, depending on the type, are meant to be replaced after periods
ranging from a day to about a year. In addition, RGP lenses can be marked to
show which lens is for which eye, and they're less likely to tear or rip, making
them easier to handle. However, it often takes several weeks to get used to
wearing rigid lenses, compared with several days for soft.
Many changes are occurring in the world of disposable (defined by the FDA as
used once and discarded) and frequent- or planned-replacement contacts. The
latest innovations include daily disposables, bifocals and toric contacts for
"It's healthier to replace lenses more often," says James Saviola,
O.D., chief of the vitreoretinal and extraocular devices branch in the FDA.
"And if you reuse your lenses, you need to do something more than store
them in saline solution." The FDA approved in 2000 the first "no-rub"
cleaning solution for contact lenses. The solution adds a safeguard for people
who do not rub their lenses--but should--when cleaning. The no-rub directions
for this first solution initially applied to lenses replaced within a month
or less. Now, it has been expanded to include lenses that are replaced after
a month or more. Other products also are available that have no-rub directions
for lenses replaced within a month. But Saviola reminds people that in some
cases, rubbing is still necessary to keep their lenses clean.
A new generation of lens materials
is being studied. Lenses made of
these materials provide a greater
amount of oxygen permeability, says
Saviola. Two types have received
FDA approval, one for seven days
of continuous wear, the other for
30 days. Others, such as the 30-day
continuous wear contact, now are
The most serious safety concerns with any contact lens deal with overnight
use, or extended-wear. Rigid or soft, wearing these types of contacts overnight
increases the risk of corneal ulcers--infection-caused eruptions on the cornea
that can lead to blindness. Symptoms include vision changes, eye redness, eye
discomfort, and excessive tearing. Extended-wear rigid lenses also can cause
unexpected, sometimes undesirable reshaping of the cornea. Saviola advises that
keeping lenses clean, replacing them often, and wearing them as prescribed by
your eye-care specialist increases the safety of wearing contacts.
People should not wear contact lenses longer than the time prescribed by their
eye-care practitioner. But whatever he or she prescribes, be sure to ask for
written instructions and follow them carefully. Patient package inserts usually
accompany contact lenses, and Saviola emphasizes that people who are not offered
this information by their doctors should ask for it.
For those who haven't been able to wear contacts, implantable lenses may be
an option in the future.
Orthokeratology, or Ortho-K, is a procedure that uses RGP contact lenses to
change the curvature of the cornea to improve its ability to refract light and
successfully focus on objects. Unlike regular RGPs, Ortho-K RGPs have a design
that can reshape the curvature of the cornea. This method, however, does not
produce a permanent result.
With conventional Ortho-K, the lenses are worn about eight hours a day. After
the cornea has achieved the best shape for optimal vision, the lenses are worn
less frequently--perhaps for a few hours every two or three days. If someone
starts and then discontinues Ortho-K, says Saviola, the corneas will eventually
return to their natural state. People choose Ortho-K over refractive surgery
because Ortho-K's effects are not permanent.
One disadvantage of Ortho-K is that clear vision may fluctuate during the day.
Also, Ortho-K may take many months to change a person's vision. A more advanced
technique known as "accelerated Ortho-K" takes less time, and may
be recommended to achieve a rapid effect.
Since 1998, Saviola says the FDA has cleared a number of daily wear Ortho-K
lenses, but overnight Ortho-K lenses have not been approved.
The best candidates for prescription Ortho-K are people of any age who have
low amounts of nearsightedness or astigmatism. The goal is to bring the person's
vision to at least 20/40. But for some, Ortho-K will provide 20/20 vision.
Corneal Ring Segments
In 1999, the FDA approved a non-laser surgical procedure for correcting small
amounts of nearsightedness. Corneal ring segments are tiny, clear crescent-shaped
pieces of plastic polymer that are implanted in the cornea. The ring segments
reshape the cornea so that it becomes flatter, allowing it to focus light rays
onto the retina and producing sharp vision. The procedure takes about 15 minutes
and is done on an outpatient basis. Before surgery, anesthetizing drops are
placed in the eyes.
Corneal rings are still being studied to treat mild hyperopia and astigmatism,
although these uses have not been approved by the FDA. Several other intraocular
and corneal implants, from several companies, also are in various stages of
Eyeglasses--The Old Standby
In some cases, modern technology can provide the best vision correction option.
In those cases in which it can't, eyeglasses can often help. Glasses correct
refractive errors by adding or subtracting focusing power to the cornea and
lens. The power needed to focus images directly on the retina is measured in
diopters. This measurement is also your eyeglass prescription.
Like contact lenses, glasses come in all shapes and sizes, offering an array
of choices for both function and fashion. Eyeglass frames, for example, are
more durable and tout materials such as titanium and new "memory metals."
Lenses are thinner, stronger and lighter. Lens options include antireflective
coating, light-changing tints, progressive (line-free) bifocal lenses, and polycarbonate--the
most impact-resistant lens material available.
Perhaps the greatest troubling aspect for eyeglass wearers is the constant
feel of something sitting on the nose, despite such advances as featherweight
glasses. Paul Trossevin of Falling Waters, W.Va., knows all too well the uncomfortable
feeling of something permanently perched on his nose. Like a scar that never
fades, Trossevin's glasses have been with him every day since he was 4 years
old. Now 35, he says, "There was a time when I'd have done anything to
get rid of my glasses." Or so he thought.
Although he could never wear contact lenses because of the severe flatness
of his cornea, Trossevin was a candidate for laser eye surgery. But the one
thing he was unable to obtain from any doctor was a guarantee that after surgery
he wouldn't see starbursts and halos around lights--a big concern since he drives
a good part of the day and plays baseball at night. "The guarantee was
everything," he says. "When he couldn't give me that, suddenly my
glasses took on new meaning--a guarantee of the good eyesight they have given
me for over 30 years."
Among some of the more intriguing developments in the vision-correction pipeline
is an alternative to LASIK, called LASEK, a new avenue for refractive surgeons
that disturbs less corneal tissue than its sound-alike counterpart. There's
also talk of investigational devices that could be placed inside the eye to
correct refractive errors. Over the next decade, there are sure to be improvements
in current techniques and technologies, in addition to new procedures.
While you can't do anything about age or genetic makeup, you can eat a balanced
diet, wear sunglasses that block ultraviolet light, and get regular eye exams
to help maintain good vision. Regular eye exams are important because they can
detect early signs of disease long before the disease leads to vision loss.
Doctors recommend that everyone have an eye exam shortly after birth, and at
least every few years until age 40. After that, the eyes should be routinely
checked every 2 or 3 years.
Buying Contact Lenses by Phone, Mail or the Internet
If you buy contact lenses--an FDA-regulated product--on the Internet, over
the phone, or by mail, the agency wants you to be well-informed. While such
purchases are often a convenient and economical way to get your lenses, consumers
need to exercise caution when using alternatives to a prescription from an eye-care
specialist, or reputable pharmacy. The following information and tips can help:
- Get regular eye exams. You may have problems with your eyes that you are
not aware of, and your contacts may not correct your vision properly. Some
untreated infections can lead to blindness.
- Have an eye-care specialist check to make sure that your contact lenses
fit properly and that the contact lens prescription was filled properly. Failure
to do so could cause discomfort or damage to your eyes.
- Beware of attempts to substitute a different brand than what you normally
wear. There are differences in water content and shape between brands. The
choice of which lens is right for you should be made only based on examination
by your eye-care specialist, not over the phone or the Internet.
- Request the manufacturer's written patient information for your contact
lenses. It will give you important information, as well as instructions for
- The minimum elements contained on a valid contact lens prescription should
include your name, doctor's name, contact lens brand name and material, expiration
date (if mandated by your state), and lens measurements, including power,
diameter and base curve.
- Make certain your contact lens prescription is current when ordering. The
expiration date is currently set by each state. Some states require one- or
two-year expiration dates, while other states leave it to eye care-specialists
to decide. Never order lenses using a prescription that has expired.
- Be sure the lenses the company sends matches your prescription exactly.
Check that you have the brand and lens name you ordered, and that the numbers
indicating power, sphere, cylinder and axis (if any), diameter, and base curve
are the same as on your prescription. This information is required to appear
on the contact lens package or container.
- If you think you have received an incorrect lens, check with your doctor.
Don't accept substitutes for any contact lens unless your doctor approves.
- Some Internet sites ask for information about your doctor so that they
can check the prescription. If they do check and receive a verbal OK, then
they have complied with the Federal prescription device regulation. If the
company does not check, they have not obtained a valid prescription. Some
state laws require that a written prescription be presented.
- Order your contacts from a supplier you are familiar with and know is reliable.
- You won't break any laws if you buy lenses on the Internet, by phone, or
through the mail without a prescription, but you should know that the company
is selling you a prescription device as if it were an over-the-counter device.
This violates federal regulation. Be wary when companies tell you they will
check with your doctor to confirm the prescription. They don't always check.