|
Home > Archive > Lasik Eyes Surgery > May 2005 > Aberrations and Contrast Loss after LASIK
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
Aberrations and Contrast Loss after LASIK
|
|
| gospa68@aol.com 2005-05-06, 5:58 pm |
| Ocular Higher-Order Aberrations and Contrast Sensitivity after
Conventional Laser In Situ Keratomileusis
Authors - Nayori Yamane,1 Kazunori Miyata,2 Tomokazu Samejima,2
Takahiro Hiraoka,1 Takahiro Kiuchi,1 Fumiki Okamoto,1 Yoko Hirohara,3
Toshifumi Mihashi,3 and Tetsuro Oshika1
1From the Department of Ophthalmology, Institute of Clinical Medicine,
University of Tsukuba, Tsukuba, Japan; the 2Miyata Eye Hospital,
Miyazaki, Japan; and the 3Topcon Research Institute, Tokyo, Japan.
PURPOSE. To investigate prospectively the relation between induced
changes in higher-order aberrations of the eye and changes in contrast
sensitivity by conventional laser in situ keratomileusis (LASIK) for
myopia.
METHODS. In 200 eyes of 110 consecutive patients (mean age, 32.7 =B1 8.4
years) undergoing LASIK, ocular aberrations and contrast sensitivity
function were determined before and 1 month after surgery. The amount
of myopic correction was 5.2 =B1 2.8 D (range, 1.0-13.0). Ocular
higher-order aberrations were measured for a 4-mm pupil using the
Hartmann-Shack wavefront analyzer (KR-9000PW; Topcon, Tokyo, Japan).
The root mean square (RMS) of the third- and fourth-order Zernike
coefficients was used to represent coma- and spherical-like
aberrations, respectively. Total higher-order aberrations were
calculated as the RMS of the third- and fourth-order coefficients.
Contrast sensitivity and low-contrast visual acuity were measured. From
the contrast sensitivity data, the area under the log contrast
sensitivity function (AULCSF) was calculated.
RESULTS. LASIK significantly improved logMAR best corrected visual
acuity (Wilcoxon signed-rank test, P < 0.001), but significantly
reduced AULCSF (P < 0.001) and low-contrast visual acuity (P =3D 0.007).
Total higher-order (P < 0.001), coma-like (P < 0.001), and
spherical-like (P < 0.001) aberrations were significantly increased
after LASIK. The greater the amount of achieved myopia correction was,
the more the changes in contrast sensitivity function and ocular
higher-order aberrations were. The induced changes in AULCSF by LASIK
showed significant correlations with changes in total higher-order
(Pearson r =3D -0.221, P =3D 0.003), coma-like (r =3D -0.205, P =3D 0.006),
and spherical-like (r =3D -0.171, P =3D 0.022) aberrations. The changes
in logMAR low-contrast visual acuity by surgery significantly
correlated with changes in total higher-order (r =3D 0.222, P =3D 0.003),
coma-like (r =3D 0.201, P =3D 0.007), and spherical-like (r =3D 0.207, P =
=3D
0=2E005) aberrations.
CONCLUSIONS. Conventional LASIK significantly increases ocular
higher-order aberrations, which compromise the postoperative contrast
sensitivity function.
| |
| Glenn - USAEyes.org 2005-05-06, 10:52 pm |
| >CONCLUSIONS. Conventional LASIK significantly increases ocular
>higher-order aberrations, which compromise the postoperative contrast
>sensitivity function.
This is one of the reasons we recommend every potential refractive
surgery patient be evaluated for higher order aberrations before
making a decision about refractive surgery. See
http://www.usaeyes.org/faq/subjects...ustom_lasik.htm
Glenn Hagele
Executive Director
Council for Refractive Surgery Quality Assurance
Email to glenn dot hagele at usaeyes dot org
http://www.USAEyes.org
http://www.ComplicatedEyes.org
I am not a doctor.
| |
| CatmanX 2005-05-06, 10:52 pm |
| We actually know this already and this is why most (good) ophthals now
do wavefront scans and have access to wavefront guided devices.
THe reason we are getting better outcomes now is that we do know more
about what happens and are in most cases taking precautionsd in advance
of problems.
dr grant
| |
| serebel 2005-05-06, 10:52 pm |
| Which is how all surgical techniques evolve.
SErebel
| |
| Sandy - LASIKdisaster.com - LASIKmemorial.com 2005-05-07, 8:57 am |
| Wavefront LASIK also increases higher order aberrations, although not
as severely, but Glenn forgot to mention that tidbit.
| |
|
|
| Ragnar 2005-05-07, 8:57 am |
| What is this WE? You are talking about ophthalmologists having
wavefront scans.. then you say "we are getting better outcomes"
implying that you are an ophthalmologist.
On 6 May 2005 19:47:28 -0700, "CatmanX" <grantm@connexus.net.au>
wrote:
>We actually know this already and this is why most (good) ophthals now
>do wavefront scans and have access to wavefront guided devices.
>
>THe reason we are getting better outcomes now is that we do know more
>about what happens and are in most cases taking precautionsd in advance
>of problems.
>
>dr grant
| |
| BarnardClassics 2005-05-07, 10:52 pm |
| Yes, surgeons do wavefront scans but they certainly don't share the 'before
and after' results with patients to show them how many aberrations were
induced during their procedures! It's a myth that wavefront LASIK actually
'goes after' your natural aberrations to 'fix' them. All wavefront does is
increasespherical aberration a bit less by doing a bettter job ablating the
periphery. Meanwhile wavefront LASIK eats more precious corneal tissue.
Wavefront LASIK still increases higher order aberrations, on average - but
about 20% LESS of an increase than with standard LASIK.
So what are these aberrometry readings really for? Mainly to see how much
damage was done - that is, to assess how much loss of visual quality a
patient may experience. Very few people have been 'fixed' by wavefrront
retreatment. Many have been made worse. Problems with tear film can affect
wavefront readings, or a problem in the flap. Lift the flap and retreat for
a flap problem? May not be all that helpful.
Are refractive surgeons getting better results these days? I think not....
LASIK is severing people's corneal nerves and causing other permanent
pathology in addition to permanent nerve loss. Too many surgeons are still
ignoring pupil size as a major factor in outcome. And LASIK is a medically
unsound procedure because it damages healthy eyes.
Dr. Mason, someone may be using your identity. There are too many typos in
'your' post.
"CatmanX" <grantm@connexus.net.au> wrote in message
news:1115434048.639292.75010@o13g2000cwo.googlegroups.com...
> We actually know this already and this is why most (good) ophthals now
> do wavefront scans and have access to wavefront guided devices.
>
> THe reason we are getting better outcomes now is that we do know more
> about what happens and are in most cases taking precautionsd in advance
> of problems.
>
> dr grant
>
| |
| serebel 2005-05-07, 10:52 pm |
| Surgeons are getting better results these days and changing the
pathology is the point of refractive surgery.
SErebel
| |
| Ragnar 2005-05-08, 8:57 am |
| Barnyard, never underestimate the number of errors Mr. Grant Mason
makes.
On Sat, 7 May 2005 19:52:49 -0400, "BarnardClassics"
<BarnardClassics@Yahoo_nospam.com> wrote:
>Dr. Mason, someone may be using your identity. There are too many typos in
>'your' post.
>
>"CatmanX" <grantm@connexus.net.au> wrote in message
>news:1115434048.639292.75010@o13g2000cwo.googlegroups.com...
>
| |
| HyperRK 2005-05-18, 11:45 am |
| So if Wavefront and Conventional do not lower HOA then why is it that vision
improves?
"Glenn - USAEyes.org" <glenn.hageleSTOPSPAM@USAEyes.org> wrote in message
news:kpno719uinmb9g9hmmnhs3mbf2upmaqul5@4ax.com...
> http://www.usaeyes.org/faq/subjects...ustom_lasik.htm
>
> Read it, Keller.
>
> Glenn Hagele
> Executive Director
> Council for Refractive Surgery Quality Assurance
>
> Email to glenn dot hagele at usaeyes dot org
>
> http://www.USAEyes.org
> http://www.ComplicatedEyes.org
>
> I am not a doctor.
| |
| Glenn - USAEyes.org 2005-05-18, 11:45 am |
| Oh, wavefront-guided LASIK, IntraLASIK, PRK, LASEK, and Epi-LASIK do
lower higher order aberrations...sometimes...not predictably.
Overall, all ablations, be they conventional or wavefront-guided,
induce higher order aberrations (HOA). Wavefront will induce less HOA
than conventional. Wavefront sometimes reduces HOA, but not always,
not predictably, and usually only when the HOA is already quite
elevated. That is one of the reasons Complex Wavefront Retreatment
(CWR) has worked as well as it has. Candidates for CWR usually have
astronomical HOA, especially spherical aberration, coma, and secondary
astigmatism (as presented in Zernike polynomials).
In nearly all instances, wavefront-guided ablation is an improvement
over conventional, but it is by no means a cure for all LASIK's
limitations.
Glenn Hagele
Executive Director
USAEyes.org
"Consider and Choose With Confidence"
Email to glenn dot hagele at usaeyes dot org
http://www.USAEyes.org
http://www.ComplicatedEyes.org
I am not a doctor.
|
| |
|
|