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Home > Archive > Lasik Eyes Surgery > August 2005 > Your night vision will most certainly be worse after LASIK.
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Your night vision will most certainly be worse after LASIK.
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| EyesRBAD 2005-08-17, 10:57 pm |
| Your night vision will certainly be worse after LASIK. Here is a discussion
of factors that can REALLY trash your post-LASIK night vision.
http://www.lasikfyi.com/articles9.html
Night Vision and LASIK
By Louis Probst, MD
It is somewhat ironic that the greatest advancements toward eliminating the
problem of night glare after LASIK have occurred at the same time that the
media and the general public have become most aware of the problem. With the
advent of lasers that allow the doctor to create what is known as a blend
zone, the incidence of night glare is dropping significantly.
The most important preoperative factor in preventing night glare following
LASIK is identify whether a patient is at risk so that the appropriate
adjustments can be made. Preoperative patient education and informed consent
should address night glare in all patients. That said, night glare can be
minimized or prevented after small-zone LASIK with several simple but useful
methods.
Pupil Size: A Critical Factor
Colvard pupillometry is the most important screening test for pupil size
because it standardizes measurement of the pupils and gives reproducible
results. Patients with larger pupils are asked about their degree of night
glare prior to surgery to determine the severity as well as to bring it to
their attention. This is done so that patients with large pupils do not
incorrectly blame postoperative night glare on their doctor, since these
patients are at increased risk for postoperative night glare. In addition,
patients with high degrees of myopia and astigmatism will typically have
smaller, more oval treatment zones, which can increase this risk of night
glare following surgery; as such, these patients are advised of the risks.
Patients with large pupils (pupillary diameters greater than 6.5 mm), higher
degrees of myopia, or astigmatism will sign an informed consent document
stating that they are aware that they have a greater chance of experiencing
postoperative night glare. These patients are told that night glare usually
improves with time but some degree of night glare can be permanent. Patients
should be counseled very carefully, especially if their
lifestyles/occupation involve a significant amount of night vision demands.
Those patients with several of the risk factors listed above may not be good
candidates for LASIK.
The importance of pupil size cannot be understated. There are other factors,
however, that often play a part in night glare. I have found that the
typical patient who exhibits night glare after LASIK is male, young (less
than 30 years of age), highly nearsighted (greater than 6.0 D), highly
astigmatic (greater than 3.0 D), with large pupils (greater than 6.0 mm in
dim light), and suffers from dry eye.
Lasers for Large Pupils
Once the risk of postoperative night glare has been identified, the
treatment should be "customized" to minimize the postoperative symptoms.
Each excimer laser differs in the functionality of its own specific tools,
which include ablation patterns, optical zones, and blend zones. This makes
it difficult to generalize about the treatment parameters that should be
used.
However, a few generalizations can be made. For example, if your eye dilates
to 7mm but the laser being used can only correct out to 6.5mm, that's .5mm
of corneal tissue that isn't being ablated. This un-ablated 'ring' is what
causes halos. This makes some lasers more likely to cause halos than others.
Specifically, LASIK procedures performed with the VISX S2 laser, which has a
maximum spherical ablation zone of 6.5 mm, can be expected to cause some
degree of postoperative night glare in the form of halos, if the pupils are
larger than these measurements in dim light.
Some lasers, however, succeed in preventing halos to an extent. Scanning
lasers such as the Bausch and Lomb 217, the Alcon-Summit Autonomous
LADARVision, and the LaserSight LSX allow programmable treatment zones with
'blend zones.' These blend zones reduce the risk of halos. Following
ablation, an abrupt division between treated cornea and untreated cornea is
left at the outer edge of the laser's treatment zone. Without blend zones,
which effectively create a smooth transition between the laser's treatment
zone and the untreated area of the cornea, this abrupt change in angle can
create visual aberration in the form of a "halo." The smoother the
transition, the less likely halos are.
For patients with larger pupils, the ablation should be centered on the
center of the pupil to avoid any 'edge glare' from a de-centered ablation.
Surgeons need to carefully monitor the corneal thickness, as the increase in
the zone sizes will dramatically increase the ablation depth. It is very
difficult to preserve an adequate amount of corneal tissue (250 microns)
when LASIK is performed with an optical zone greater than 7.0 mm.<>
Patients that do experience postoperative night glare should be seen
immediately, as the loss of ability to drive at night can be a very
stressful event. These symptoms generally subside after a period of between
3 to 6 months. During the recovery phase, the treatment of dry eyes and any
residual refractive error or monovision often improves the symptoms. For
those patients that still have difficulties, there are still treatment
options to help patients manage during the recovery phase. These include
night driving glasses, turning the car dome light on when driving, and,
although rare, the use of special drops just before night driving. For those
rare patients with persistent night glare, custom/ wavefront LASIK should
offer a refined method of enlarging the treatment zones in the next 12
months.
[Don't count on it, the industry has been promising that a new laser would
come along and 'fix us all' for years].
Louis Probst, MD, is Medical Director for TLC Chicagoland, TLC Madison, and
TLC Windsor.
| |
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| In article <1124321339.bf7bcb4dc6f16d3fc82c1fc16a58ba09@teranews>,
"EyesRBAD" <EyesRBAD@AOL_nospam.com> wrote:
> Your night vision will certainly be worse after LASIK. Here is a discussion
> of factors that can REALLY trash your post-LASIK night vision.
Interesting you should conclude that from this article, because this is
what the author actually concludes:
>With the
> advent of lasers that allow the doctor to create what is known as a blend
> zone, the incidence of night glare is dropping significantly.
--
~RT
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| serebel 2005-08-17, 10:57 pm |
|
RT wrote:
> In article <1124321339.bf7bcb4dc6f16d3fc82c1fc16a58ba09@teranews>,
> "EyesRBAD" <EyesRBAD@AOL_nospam.com> wrote:
>
>
> Interesting you should conclude that from this article, because this is
> what the author actually concludes:
>
>
> --
> ~RT
Loonies like this one don't even read what they post, so they
actually shoot themselves in the foot. They come across as extremely
stupid also.
SErebel
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