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Contact Lenses After LVC
Surgeries:
Gas permeable (GP) or hybrid
contact lenses may improve
the eyesight of people who
have less-than-perfect
results from LASIK or other
refractive surgery,
especially when another
surgical procedure or
enhancement is not possible.
The smooth, rigid surface of
these lenses can correct
optical imperfections that
eyeglasses and soft contacts
can't address, making gas
permeable contact lenses or
hybrids the best choice if
you're looking for the
sharpest vision possible.
Despite high refractive
surgery success rates,
LASIK, PRK and other laser
vision correction procedures
don't produce perfect vision
for everyone. Your results
depend a great deal on the
unique way your corneas
respond to laser energy and
how they heal after surgery.
Glare, halos and starbursts
around headlights and street
lights can sometimes be a
problem after refractive
surgery. LASIK and other
procedures can also
sometimes cause irregular
astigmatism, with
accompanying blurred and/or
distorted vision.
For most people who have
less-than-perfect vision
after refractive surgery,
problems are quite mild and
usually tolerable. But for
others, post-surgery vision
problems can decrease
overall quality of life with
side effects such as
eyestrain, headaches and
difficulty driving at night.
Post-Surgery Contact Lenses
Indications:
LASIK and other laser vision
correction procedures
reshape your eye's front
surface by removing
microscopic amounts of
tissue from the cornea.
Occasionally, this can cause
irregularities in the shape
of the cornea that can make
your vision less distinct
after surgery than it was
when you wore glasses or
contact lenses before the
procedure.
These irregularities
sometimes can be corrected
with a follow-up laser
procedure called an
enhancement. But if your
cornea is too thin for a
second surgery, or other
problems rule out an
enhancement procedure, GP or
hybrid contact lenses may be
your best solution.
Post-Surgery Gas
Permeable Contact Lenses
Because gas permeable
contacts are rigid, they
maintain their shape on the
eye - unlike soft lenses
that drape the cornea,
losing their shape.
That's significant because
the space between the cornea
and the back surface of a GP
lens is filled with tears.
This "lake" of tears covers
all the tiny irregularities
(aberrations) on the
cornea's surface. The smooth
front surface of the GP lens
then optically replaces the
irregular corneal surface,
eliminating blur and visual
distortions.
In comparison, soft contact
lenses are pliable and
conform to the surface of
the cornea. This means soft
lenses can't achieve the
same aberration-cancelling
effect that GP lenses
provide.
And conventional eyeglasses,
which do nothing to change
corneal irregularities,
cannot correct the vision
problems those
irregularities cause. These
glasses can correct only the
basic refractive errors -
nearsightedness,
farsightedness, and regular
astigmatism.
Special Contact Lens
Designs for Post-Surgery
Fittings
Because LASIK and other
laser refractive surgery can
significantly alter the
shape of the cornea, fitting
contact lenses on a
post-surgery eye is more
challenging than fitting
lenses on a normally shaped
cornea. Instead, special GP
lens designs are usually
required in these
circumstances.
These modified designs may
include a larger lens
diameter, aspheric optics or
a design where the center of
the lens is significantly
flatter than the periphery
(called a reverse geometry
design), similar to the gas
permeable lens design used
for orthokeratology to
correct nearsightedness
without surgery.
Special computerized
instruments (not needed for
regular contact fitting) are
usually required to obtain
highly accurate,
point-to-point measurements
of the post-surgery corneal
surface to obtain the best
possible fit for vision
correction. These
instruments, called corneal
topographers or
aberrometers, use the same
LASIK technology that
measures the cornea before
laser vision correction.
Because of these added
complexities, contact lens
fittings after refractive
surgery are typically more
time-consuming and involve a
higher fee than regular
contact lens fittings. Also,
if you've never worn GP
lenses before, be aware that
it takes longer to adapt to
them than to soft contacts.
You may have to wear the
lenses at least part-time
every day for several weeks
before they feel completely
comfortable.
Fitting GP contacts on an
eye that has undergone
refractive surgery requires
special skills similar to
those needed to fit lenses
on an eye with an irregular
cornea, such as an eye with
keratoconus or one that has
had a cornea transplant
procedure called a
penetrating keratoplasty.
Several lens modifications
may be required to achieve
the optimum fit, comfort and
visual acuity.
New Technologies: Hybrid
Contact Lenses and Wavefront
Glasses
Recently, two new eyewear
technologies were introduced
that offer an alternative to
GP contact lenses for
correcting irregular
astigmatism and higher-order
aberrations after eye
surgery.
One technology involves a
type of contact lens that
has a rigid gas permeable
optic zone in the center and
a soft outer skirt. Called
SynergEyes, these new
"hybrid" lenses may offer
the best of both worlds: the
aberration-correcting optics
of a rigid GP lens, combined
with comfort that often
rivals that of soft contact
lenses. Early reports
indicate SynergEyes lenses
may be equally as effective
as GP lenses in correcting
aberrations after surgery,
but may be easier to adapt
to and wear.
The second new technology is
a type of eyeglass lens that
uses LASIK-style wavefront
measurements to create a
custom lens design for each
person. In addition to
correcting common refractive
errors like nearsightedness,
these new eyeglass lenses
can also correct some degree
of irregular astigmatism and
higher order aberrations
(HOAs) caused by corneal
irregularities.
Studies suggest that these
new wavefront lenses, called
iZon High Resolution Lenses,
provide sharper vision at
night than conventional
eyeglass lenses and may be
an acceptable alternative to
GP or hybrid GP/soft contact
lenses for the correction of
post-surgical vision
problems.
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