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
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 excessive
"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
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 eyes.
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
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
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 astigmatism.
"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 being considered.
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 clinical
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
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
- 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
- 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
- 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
- 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