In customized LASIK treatment, the laser ablation
is specifically designed to treat every individual eye and
patient. A wavefront device is used to create a “power
map” of the entire cornea,
allowing the surgeon to treat small, localized areas. This
allows accurate focusing of all light rays onto the fovea
(centre of the retina)
Step 1
Aberrometer projects the laserbeam into the eye and onto
the fovea.
Step 2
Reflected laser light emerging from the eye.
Step 3
Detailed power map individual to the patient, captured
by aberrometer.
Wavefront-customized LASIK treatment is beneficial to patients
with distorted, irregular corneas and patients with large
pupils. The procedure
is most accurate for mild to moderate myopia
(100 to 700 degrees).
Customised LASIK takes longer to complete than standard LASIK
due to its expanded treatment zones and improved post-treatment
profiles. In Wavefront guided customized treatments more visual
distortions will be eliminated.
After many years of performing standard LASIK, it was discovered
that we were creating aberrations (visual distortions). Standard
LASIK most commonly causes a visual distortion called spherical
aberration. Spherical aberration causes halos and decreased
night vision.
Wavefront optimised LASIK has been designed to address this
surgically induced visual distortion – spherical aberration.
When we use the laser to alter the cornea shape, we induce
some contour distortions in the corneal periphery. Predicting
these changes and compensating for these changes leads to
a better final corneal shape (profile) and improved night
vision, especially in the prevention of halos
and glare.
This is a great advancement towards addressing a major post
operative visual problem associated with standard LASIK, i.e.
poor night vision.
A prolate cornea is a cornea that focuses all rays of light
whether in the centre or the periphery, exactly on the macula
which is the center of the retina.
After LASIK surgery, many patients are left with an oblate
cornea. This causes loss of correct focus in the periphery
of the cornea.
This causes halos and glare. Many lasers are creating oblate
corneas just by the nature of their ablation/treatment patterns.
Newer lasers, like the Allegretto Eye Q laser have the ability
to create a prolate cornea. This betters night vision and
many patients are reporting an improvement over their previous
vision at night with glasses or contact lenses. This type
of LASIK treatment has been called Custom-Q LASIK. The flattening
of the cornea is more gentle and over a larger extent of the
cornea’s periphery. There is no sudden change in corneal
contour. This shape change in treatment pattern has taken
years of research and development as each eye is different
and requires a highly customized approach.
At present, the shape of a person’s cornea is measured
and the amount of “prolateness” or Q value is
calculated. The treatment pattern is designed to maintain
or improve the patient’s natural “prolateness”.
All predators like eagles and humans have a prolate cornea.
Animals preyed upon, like frogs, have oblate corneas. Eagles
require sharp distance vision to catch prey while frogs need
wide (but blurred) peripheral vision to make sure they are
not caught by predators. Frogs do not need good distance vision
as their food is usually within a few centimeters of their
reach. Personally, I rather be an eagle than a frog!
PerfectShape™ LASIK or Corneal Wavefront Q-Adjusted LASIK - Reduces Risk of Poor Night Vision
Wavefront guided, wavefront optimized, Zyoptix, Aspheric LASIK? Confused? These are all different ways to treat the cornea to correct shortsightedness and astigmatism.
Corneal Wavefront Q-Adjusted LASIK is the latest software development that Dr. Jerry Tan has developed since 2005. Pioneering this technique Dr. Tan has just presented results of this surgery at the ESCRS (European Society of Cataract and refractive Surgeons) in London England (9th -13th September 2006). He has also presented this treatment technique at the Wavelight Laser user’s meeting in Vienna, Austria in June 2006. This treatment program marries the best aspects of all previous treatment programs into a single entity and improves on all previous treatment profiles. This results in a “PerfectShape™ Cornea” after this type of LASIK surgery. Jerry Tan Eye Surgery is the only centre in Asia providing this treatment. Doctors from Australia, Hong Kong, Korea, Taiwan and India are coming to learn this new treatment modality.
Night Vision Problems
The Achilles heel of standard and other LASIK and Epi-LASIK procedures is that they expose patients to a higher risk of poor night vision. This means patients’ night vision may be distorted by glare and halos. It is now possible to reduce this risk with “PerfectShape™LASIK”.
Results of a Night Vision survey done on 78 participants, 3 months after their “PerfectShape™LASIK” surgery.
Cornea with all the inherent imperfections found in all patients’ pre-LASIK surgery
Cornea treated with Wavefront guided treatment – does not take into consideration original shape/contour of the cornea. It does not anticipate induced aberrations caused by the LASIK procedure.
The Aspheric or Q-adjusted treatment is a very basic customization. It does not take into consideration the aberrations like coma and trefoil. This leaves behind imperfections that will deteriorate night vision in most patients. It treats only one of the three major aberrations.
The inherent imperfections are smoothed over and the cornea reshaped into a “perfect” shape. It takes the original corneal contours, wavefront into consideration and anticipates the induced aberrations caused by the LASIK procedure. It treats all aberrations as well as reduces aberrations.
This is PerfectShape™LASIK.
Traditionally, doctors have used an instrument called a microkeratome for the creation of corneal flaps. The microkeratome is a hand-held blade that moves across the eye, cutting the corneal flap as it goes. While LASIK is extremely safe, if complications do occur the microkeratome is most often the cause.
One of the latest developments in LASIK is the development
of a Femtosecond laser. At present, Intralase is the most
established company producing a Femtosecond laser that is
FDA approved, to create the LASIK flap.
Intralase does not cut the flap; It is a 100% blade-free approach to creating your corneal flap.Tiny pulses of laser light, a quadrillionth of a second each, pass harmlessly through the outer portion of your cornea and form a uniform layer of microscopic bubbles just beneath the surface of your eye to split it into a superficial (the flap) and deep layer (the bed). It merges thousands of these bubbles into a contiguous layer to create the flap.
The exact dimensions of this layer of bubbles are determined by Dr Tan based on what’s best for your eye, and are computer controlled for maximum precision – things that are not possible with a hand-held blade. The Intralase flap creation process currently takes about 20 to 25 seconds.
We have been able to offer this option to create the flap since 2004. With the Intralase 30K in December 2005 and our recent upgrade in 2006 to the 4th generation 60K, we are now able to offer even better safety, precision and predictability with a faster speed.
Why Intralase?
To create the LASIK flap with a microkeratome takes 10 seconds.
Intralase takes about 20 to 25 seconds depending on the size
of the flap. So why use Intralase?
Safety
Intralase has the edge in safety.
Buttonholes and partial flaps can occur with a microkeratome
more frequently than with the Intralase. Microkeratome buttonholes
occur 1 in 2000 cases.
Flaps created using Intralase are also less likely to displace post-operatively.
Flap Configuration
The depth, size and contour of the flap is more even, accurate
and predictable with the Intralase. This is especially so
for very flat or very curved corneas.
Aberrations
Microkeratome flaps create slightly more optical aberrations/
distortions than the Intralase flap. The Intralase Method delivers outstanding visual results: more patients achieve vision that is 20/20 or better when the Intralase Method is used. Patients also report better quality of vision overall, particularly in terms of their ability to see well in low light, such as at dusk or at night.
Very Small Eyes
The Intralase suction ring is soft and more comfortable in the small eye.
Dry Eye
Patients who have undergone Intralase have reported less dry eye, a common temporary side effect of LASIK.
Disadvantages of Intralase
Inflammation
Inflammation can occur more frequently with the Intralase, especially if the laser power is set at an incorrect and excessive power. However, this inflammation is minimal with the 4th generation laser and can be controlled by topical eyedrops.
Expense
Intralase is a much more expensive machine to purchase and maintain.
Both techniques are very safe, with the Intralase having
an advantage in certain eyes.
It is best to discuss with your LASIK surgeon which technique
is best for you.
